FOUS11 KWBC 220711
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
211 AM EST Sat Feb 22 2025

Valid 12Z Sat Feb 22 2025 - 12Z Tue Feb 25 2025



...Pacific Northwest through the Northern Rockies...
Days 1-3...

A closed mid-level low tracking slowly south of the Aleutians will
shed lobes of vorticity eastward and onshore the Pacific Coast,
spreading precipitation from the Pacific Northwest through the
Northern Rockies into early next week.

Generally W to SW flow will persist across the Pacific during this
time, with enhanced confluence south of the Aleutian Low enhancing
moisture advection and IVT as an atmospheric river (AR). Both ECENS
and GEFS probabilities indicate that IVT will almost certainly

90%) exceed 500 kg/m/s, with potentially 3 consecutive days of

IVT exceeding 250 kg/m/s surging onshore beginning this evening.
Within this moisture plume, PWs are progged by NAEFS to exceed the
99.5 percentile of the CFSR database, especially late D1 through
the end of D2 from the WA/OR coasts to as far inland as the Central
Rockies. Shortwaves/vorticity spokes rotating within this flow will
cause periodic enhancement to ascent leading to heavier and more
widespread precipitation. Although the timing of these features is
not fully agreed upon by the guidance, consensus suggests bouts of
heavier precipitation are likely beginning late D1 and again late
D2. While this will result in heavy snow in higher terrain features
across the region through the period, snow levels will climb
steadily within the AR/accompanying WAA. Snow levels begin the
period around 4000-6000 ft, then climb to as high as 7000-9000 ft,
especially during D2. This will keep most significant snow
accumulations above area pass levels.

Although waves of heavy snow are likely in the higher terrain each
day, the heaviest accumulations are forecast on D2 when WPC
probabilities support a high risk (>70%) for more than 6 inches of
snow across the higher WA Cascades, the Northern Rockies near
Glacier NP, the Sawtooth, and near the Grand Tetons/Yellowstone NP.
During D3, the highest probabilities shift back into the WA/OR
Cascades with slightly lower snow levels supporting high
probabilities (>70%) for more than 6 inches, and 3-day snowfall in
the Cascades could be measured in several feet above 5000 ft
elevation. Additionally, some light icing is expected in the
Columbia Basin and parts of eastern OR where WPC probabilities D2
reach 10-30% for up to 0.1" of ice.

Weiss

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FOUS11 KWBC 230738
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
238 AM EST Sun Feb 23 2025

Valid 12Z Sun Feb 23 2025 - 12Z Wed Feb 26 2025

...Pacific Northwest through the Northern Rockies...
Days 1-3...

Long duration atmospheric river (AR) begins before the forecast
period, and continues through Tuesday. This AR is driven by
confluent mid-level flow overlapped by multiple impressive Pacific
jet streaks, resulting in pronounced onshore flow of moisture. The
accompanying IVT has a high probability (>80% from ECENS and GEFS)
of exceeding 500 kg/m/s through Monday, with a slow wane
thereafter. Within this plume of moisture, forcing for ascent will
be periodically enhanced by shortwave troughs rotating through the
flow as impulses shed from a strong closed mid-level low out over
the Pacific Ocean. Each of these impulses will produce enhanced
ascent to expand and intensify the accompanying precipitation,
leading to rounds of heavy snow from the Cascades through the
Northern Rockies. However, the WAA within the AR will lift snow
levels to as high as 8000 ft, before latitudinal variations develop
on either side of a stalled front.

For D1, a closed 500mb low pushing onshore British Columbia will
pulse a lobe of vorticity into WA state, accompanied favorably by
coupled jet streaks. This will combine with a cold front pushing
eastward to enhance ascent and drive rounds of heavy precipitation
from northern CA through the Northern Rockies, with upslope flow
into terrain features resulting in the heaviest accumulations of
precipitation. Snow levels during this time will rise to generally
6000-8000 ft, keeping snow confined above pass levels. However,
where it does snow, accumulations will be significant as reflected
by WPC probabilities that indicate a high risk (>70%) for 8+ inches
in the Sawtooth, Northern Rockies near Glacier NP, and the Tetons of WY.

This first front will then become elongated west-east as the
mid-level pattern becomes flattened in response to a sharper trough
approaching from the West. This will allow some colder air to drain
southward but remain confined generally to WA, northern ID, and MT,
with a sharp gradient in snow levels existing along this boundary
(3000 ft north, 6000 ft south). This will be relatively short lived
however, as the stronger trough axis drives a potent closed low and accompanying surface low towards the WA/OR coast late Monday. This
will once again result in enhanced ascent through WAA, PVA, and
upper diffluence, with a second surge in precipitation expanding
east across the area. Snow levels climb again to as high as 6000 ft
in many areas late Monday into early Tuesday, before the associated
cold front drives eastward by the end of the period. While this
will cause snow levels to fall quickly, it will also result in
rapid drying of the column, bringing an end to the heavy
precipitation.

D2 snowfall is likely to be heaviest along the spine of the
Cascades and into the Olympics of WA, where WPC probabilities are
high (>90%) for 8 inches, and locally 1-3 feet is possible in the
highest elevations. During D3 the heaviest precipitation spreads
inland as far as the Northern Rockies and into the vicinity of
Yellowstone NP, but the heaviest accumulations are likely again
across the WA Cascades where WPC probabilities are above 50% for an
additional 8+ inches of snow.


Weiss


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FOUS11 KWBC 240647
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
147 AM EST Mon Feb 24 2025

Valid 12Z Mon Feb 24 2025 - 12Z Thu Feb 27 2025

...Pacific Northwest through the Northern Rockies...
Days 1-2...

Ongoing atmospheric river (AR) will intensify and continue through
today and into Tuesday before eroding as the driving trough pivots
inland. Until that occurs, persistent advection of moisture on IVT
exceeding 500 kg/m/s is expected into WA/OR and then spilling as
far east as portions of the Northern Rockies. This AR will be
driven by confluent flow downstream of an impressive closed low
(NAEFS 500-700mb height anomalies below -1 sigma) which will be
overlapped by a strengthening upper jet streak. Weak impulses
shedding eastward from this closed low as it moves into British
Columbia will help to periodically enhance ascent, with additional
lift likely in the vicinity of a surface low moving near the Strait
of Juan de Fuca Tuesday morning. Impressively confluent flow will
keep moisture advection nearly perpendicular to the Cascades and
other N-S ranges, leading to strong upslope ascent as well.

The guidance is well aligned overall with the synoptic and
mesoscale features, leading to high confidence in the evolution of
this event. However, the consensus has trended colder Monday in
areas north of a draped front from west-east near the WA/OR border.
This will keep snow levels more suppressed, generally remaining
around 3000-3500 ft in WA, ID, MT D1 before a slow rise occur late
D1 due to the enhanced WAA as a warm front lifts north ahead of
the surface low. Thereafter, snow levels crash again quickly during
D2 as the accompanying cold front pivots east. Despite the lowering
snow levels D2, this will occur in tandem with a drying column,
which indicates most of the heavy snow should accumulate only at
the higher elevations thanks to rapid wane of precipitation
coverage and intensity by the second half of D2.

WPC probabilities for heavy snow accumulating to more than 6 inches
are high (>90%) in the Olympics and along the crest of the Cascades
D1, with locally 2-3 feet possible at the highest elevations.
Additionally, impactful pass-level snow is likely especially at
some of the higher passes like Washington Pass. During D2, heavy
snow continues across the Cascades but also expands eastward
towards the Northern Rockies. WPC probabilities D2 are high (>70%)
for 6+ inches across the higher elevations of these ranges, before precipitation winds down into D3.


Weiss



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FOUS11 KWBC 250630
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
130 AM EST Tue Feb 25 2025

Valid 12Z Tue Feb 25 2025 - 12Z Fri Feb 28 2025

...Pacific Northwest through the Northern Rockies...
Day 1...

Strong surface low pressure will be moving eastward near the Strait
of Juan de Fuca, pivoting onshore beneath a strong but filling
upper level shortwave trough. This upper feature will weaken
rapidly as it gets replaced by upper level ridging, resulting in
the surface low eroding as it moves across WA state. E/SE of this
stacked system, the ongoing atmospheric river (AR) will persist
another 12 hours as reflected by GEFS/ECENS IVT probabilities,
surging moisture into the Pacific Northwest and Northern Rockies
D1. The lingering precipitation D1 is expected to be lighter than
the heavy amounts that have fallen already, but still should
result in heavy snow in the WA Cascades and Northern Rockies,
including the Bitterroots and Lewis Range, especially above
3000-3500 ft. In these areas, WPC probabilities for 6+ inches of
snow are high (>90%), and pass level impacts will continue until
snow wanes at the end of D1.


...Northeast...
Day 3...

A modest wave of low pressure will move northeast from the Great
Lakes across New England Thursday into Friday, with an accompanying
cold front trailing in its wake. The low will likely track across
central New England, with the accompanying WAA causing
precipitation to expand in the form of snow across northern New
England. Although the system will be fast moving, brief heavy snow
is likely in the higher terrain of the White Mountains of NH where
WPC probabilities reach 30-50% for 4+ inches of accumulations.
Later D3, as the cold front passes to the east, post-frontal
upslope flow will develop into the Adirondacks and northern Greens,
with modest lake enhancement occurring into the Tug Hill Plateau.
In these areas, WPC probabilities for 4+ inches reach 30-50% as
well, but generally later in the D3 period than what will occur
across the NH terrain.


Weiss

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FOUS11 KWBC 260711
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
211 AM EST Wed Feb 26 2025

Valid 12Z Wed Feb 26 2025 - 12Z Sat Mar 01 2025

...Upper Great Lakes through the Northeast...
Days 2-3...

A series of shortwave troughs moving through the flow this week
will result in an amplified longwave trough deepening across the
eastern CONUS. This will create period of active wintry weather
from the Upper Great Lakes through northern New England.

The first of these shortwaves will pivot southeast from the Upper
Midwest Wednesday night, reaching the Great Lakes before 12Z
Thursday and then pushing into New England on Friday. This will
sharpen the associated longwave trough across the east, driving a
cold front across the region, which will be draped from a wave of
low pressure likely developing downstream of the lead shortwave. As
this low moves E/NE from Michigan to New England, accompanying WAA
will help spread precipitation northeastward as PWs surge to +1 to
+2 sigma according to NAEFS ensemble tables. The surface low
tracking across northern New England will allow precipitation to
start as snow in many places from Upstate New York into New
England, but changeover to a mix and then rain across all but the
higher terrain of the Adirondacks, Whites, and northern Maine.

Then as the subsequent cold front pushes through on Thursday,
upslope flow in a still moist column will drive periods of moderate
snowfall across the Adirondacks, Greens, and Tug Hill Plateau, the
latter aided by lake Ontario moisture enhancement. This will
result in locally heavy snow exceeding 4 inches as reflected by WPC probabilities D2 that are moderate to high (30-70%) across these
mountain ranges, with locally 6+ inches possible in the higher
terrain and across the Tug Hill Plateau.

A subsequent shortwave will race southeast immediately on the heels
of this first system, pushing an Alberta Clipper type low from
northern MN early Friday to New England Saturday. This system will
be compact and progressive, but a strengthening shortwave and
favorable positioning of an upper level jet streak will produce
significant ascent to spread moderate to heavy precipitation across
the region. Although this system will Alas be progressive, a
region of overlapping frontogenesis and deformation north of the
surface low will result in an axis of heavier precipitation, and
since the column will be quite cold behind Thursday's cold front,
this will produce a swath of heavy snow from the Arrowhead of MN,
across the U.P. of MI, eastward into northern New England. WPC
probabilities D3 are high (>70%) for 4+ inches from the eastern
U.P. through the far northern portion of the L.P., with 30-70%
chances for 4+ inches encompassing that region as far west as the
tip of the Arrowhead to as far east as the western Adirondacks.

Weiss


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FOUS11 KWBC 270803
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
303 AM EST Thu Feb 27 2025

Valid 12Z Thu Feb 27 2025 - 12Z Sun Mar 02 2025


...Northeast...
Day 1...

The first in a pair of winter storms tracks through the Northeast
today. NAEFS shows a sub 1004mb low tracking through the eastern
Great Lakes that is below the 10th percentile. This low is also
directing a narrow >500 kg/m/s IVT towards New England that is
above the 90th climatological percentile. As anomalous moisture is
directed towards the northern Appalachians, a sufficiently cold
air-mass located over New England will support periods of snow,
particularly in the northern Appalachian ranges. With low-level WAA
and 290k isentropic glide aloft, periods of snow will be ongoing
from the Adirondack on east through the Green and White Mountains
this morning. As low pressure tracks into the Champlain Valley
around midday, snow will track into the northern two-thirds of
Maine with a wintry mix just north of the Maine coastline. The
storm will race northeast into the St. Lawrence Valley of southern
Quebec by Thursday evening with a dry slot moving in aloft that
effectively shuts off most accumulating snowfall beyond 00Z Friday.
WPC probabilities show low-to-moderate chances (30-50%) for
snowfall >6" in the peaks of the Green and White Mountains. Most
snowfall totals >500ft in elevation that are not in the Green and
White Mountains are most likely to see anywhere from 1-4" of
snowfall through Thursday afternoon. The WSSI does show a swath of
Minor Impacts from southern VT and central NH on east through the
southern half of Maine. Residents in these areas could contend with
hazardous driving conditions, particularly in areas with complex
terrain.


...Upper Great Lakes through the Northeast...
Days 2-3...

An unusually strong clipper system diving southeast from southern
Canada will head for the Upper Great Lakes on Friday. The storm
will reside beneath the diffluent left-exit region of a 90-100 knot
500mb jet streak, while also sporting an unusually strong NWrly IVT
that surpasses 300 kg/m/s on the western flank of the Clipper. The
low-level circulation at 850mb is also rather potent with heights
that are below the 0.5 climatological percentile by 18Z Friday
according to NAEFS. This equates to what would be a "front-end
thump" of heavy snow late Thursday night across the Minnesota
Arrowhead, then across the Michigan U.P. and far northern Michigan
Friday morning where the best 850mb FGEN ensues. Just north of the
850mb FGEN is where snowfall rates of 1-2"/hr are possible for
several hours. A dry slot and warming boundary layer should limit
snowfall over the Michigan U.P. and northern Michigan Friday
afternoon. As the storm heads east though, additional snow is
likely on the back side of the storm as low-level CAA over Lake
Superior increases Friday evening. Snow should taper off by
Saturday morning in the Upper Great Lakes. WPC probabilities show moderate-to-high chances (50-70%) for snowfall totals >6" in the
MN Arrowhead with similar chances for >8" in the Keweenaw
Peninsula, the, Huron Mountains, and eastern Michigan U.P..
Localized amounts approaching a foot are possible closer to Sault
Ste. Marie, MI.

The storm continues its march east into southern Ontario Friday
evening with the same method of producing periods of heavy snow as
far east as the Tug Hill and Adirondacks of northern New York.
Unlike the Upper Great Lakes, however, the storm track is farther
north through the St. Lawrence Valley. WPC's Snowband Probability
Tracker, utilizing the 00Z HREF guidance, shows the potential for
1"/hr rates from the Tug Hill to as far east as the Green and White
Mountains Friday night. The dryslot and warming low level-
temperatures arrive Saturday morning with only northern Maine
likely to still see periods of moderate-to-heavy snow through rest
of the day Saturday. Snow should taper off throughout the Interior
Northeast by Saturday night. WPC probabilities show moderate-to-
high chances (50-70%) for snowfall >6" in the Tug Hill and
Adirondacks neighboring the Tug Hill through Saturday morning.


Mullinax


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FOUS11 KWBC 280808
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
308 AM EST Fri Feb 28 2025

Valid 12Z Fri Feb 28 2025 - 12Z Mon Mar 03 2025


...Upper Great Lakes through the Northeast...
Days 1-2...

An unusually strong clipper system (MSLP below the first
climatological percentile per the ECMWF) diving southeast from
southern Canada will head for the Upper Great Lakes this morning.
The storm will reside beneath the diffluent left-exit region of a
90-100 knot 500mb jet streak, while also sporting an unusually
strong NWrly IVT that surpasses 300 kg/m/s on the western flank of
the surface low. The low-level circulation at 850mb is also rather
potent with heights that are below the 0.5 climatological
percentile by 18Z Friday according to NAEFS. This equates to what
is effectively a "front-end thump" of heavy snow that began
overnight in the Minnesota Arrowhead and is now heading for the
Michigan U.P. and far northern Michigan today where the best 850mb
FGEN occurs. The 00Z HREF suggests snowfall rates of 1-2"/hr are
possible for several hours this morning. A dry slot and warming
boundary layer should limit snowfall over the Michigan U.P. and
northern Michigan Friday afternoon, resulting in a narrow swath of
heavy snow. As the storm heads east though, additional snow is
likely on the back side of the storm as low-level cold-air
advection (CAA) over Lake Superior increases Friday evening. Snow
should taper off by Saturday morning in the Upper Great Lakes. WPC probabilities show moderate-to-high chances (50-70%) for snowfall
totals >6" in the MN Arrowhead with similar chances for >8" in the
Keweenaw Peninsula, Huron Mountains, and eastern Michigan U.P..
Localized amounts approaching a foot are possible closer to Sault
Ste. Marie, MI and neighboring communities to the south along the coast.

The storm continues its march east into southern Ontario Friday
evening with the same method of producing periods of heavy snow as
far east as the Tug Hill and Adirondacks of northern New York.
WPC's Snowband Probability Tracker, utilizing the 12Z HREF
guidance, shows the potential for 1"/hr rates from the Tug Hill to
as far east as the Green and White Mountains Friday night. Unlike
the Upper Great Lakes, however, the storm track is farther north
through the St. Lawrence Valley. This burst of heavy snow will
eventually give way to diminishing snowfall rates late Friday night
and into Saturday morning in these areas. By Saturday morning,
only northern Maine likely to still see periods of moderate-to-
heavy snow through rest of the day Saturday. However, as the
Arctic front approaches midday Saturday, steepening lapse rates
and strong upper-level ascent aloft is a recipe for snow squalls.
Plummeting temperatures could result in quick accumulations on some
surfaces, but the biggest concern is for dramatic reductions in
visibilities within impacted areas of northern New York and as far
east as northern New England Saturday afternoon. Travelers on
roadways should be sure to have a reliable way to receive snow
squall warnings should they be issued on Saturday. Snow should
gradually taper off throughout the Interior Northeast by Saturday
evening, with some lake-effect showers lingering into Sunday. WPC
probabilities show moderate-to-high chances (50-70%) for snowfall

6" in the Tug Hill and Adirondacks neighboring the Tug Hill

through Saturday morning. Similar probabilities for >4" of snowfall
are depicted across northern Maine, as well as the Green and White
Mountains through Sunday morning. Localized amounts topping 8" are
possible in the tallest peaks of the Green and White Mountains.


...California & Great Basin...
Day 3...

A closed upper-low approaching California on Sunday will direct an
IVT that is topping out not much higher than 250 kg/m/s at the
Sierra Nevada and Southern California ranges. 850mb and 700mb winds
topping the 90th climatological percentile (per NAEFS) may aid in
some modest upslope flow, but this IVT is not particularly strong,
which should limit most heavy amounts to the highest/more remote
elevations. Snow levels will be as low as 4,000ft from the Sierra
Nevada on east into the Great Basin, but the heavier amounts will
generally be confined to elevations above 6,000ft. Snow will fall
heaviest over the Sierra Nevada and as far north as the
Shasta/Siskiyou Sunday afternoon and into Sunday night. As the
upper low approaches Sunday night, Pacific moisture will spill over
into the Great Basin with moderate-to-heavy snowfall along the
ridge lines of central Nevada Sunday night and into Monday. WPC
probabilities depict moderate-to-high chance probabilities (50-70%)
for snowfall >8" at elevations above 7,000ft in the Sierra Nevada
through Monday morning. Similar moderate-to-high chance
probabilities for >4" of snowfall exist along the ridges of
central Nevada through Monday morning.


Mullinax



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FOUS11 KWBC 010805
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
305 AM EST Sat Mar 1 2025

Valid 12Z Sat Mar 01 2025 - 12Z Tue Mar 04 2025


...Great Lakes through the Northeast...
Day 1...

The winter storm responsible for periods of heavy snow in parts of
northern Michigan marches east into southern Ontario today. Periods
of snow will stick around from the White Mountains to northern
Maine this morning. Following a break in the snow this morning, the
passage of a strong Arctic front paired with a deep upper trough
approaching from the west will provide a source of lift aloft.
Combine increasing surface-based heating that steepens low-level
lapse rates, and the stage is set for scattered snow showers and
snow squalls from the Great Lakes and Upper Ohio Valley on east
through the Interior Northeast throughout much of the day Saturday.
Plummeting temperatures could aid in rapid snowfall accumulations
in wake of the cold frontal passage, but there is also a concern
for bursts of heavy snow and gusty winds that cause dramatic
reductions in visibility for those on roadways and for aviation.
Travelers on roadways should be sure to have a reliable way to
receive snow squall warnings should they be issued. Snow should
taper off not long after sunset Saturday evening, although some
residual lake-effect snow showers may stick around into parts of
Saturday night. WPC probabilities through 06Z Sunday show moderate-
to-high chances (50-70%) for >4" of additional snowfall in the Tug
Hill, the White Mountains, and far northern Maine.


...California & Great Basin...
Days 2-3...

A closed upper-low tracking into California on Sunday will direct
an IVT topping out around 250 kg/m/s at the Sierra Nevada and
Southern California ranges. While SWrly low-level winds may provide
some marginal upslope flow enhancement, this IVT is not
particularly strong, thus limiting most heavy amounts to the
highest/more remote elevations. Snow levels are expected to be as
low as 4,000ft from the Sierra Nevada on east into the Great Basin,
but the heavier amounts will generally be confined to elevations
above 6,000ft. Snow will fall heaviest over the Sierra Nevada and
as far north as the Shasta/Siskiyou Sunday afternoon and into
Sunday night. As the upper low approaches Sunday night, Pacific
moisture will spill over into the Great Basin with moderate-to-
heavy snowfall along the 6,000-7,000ft ridge lines of central
Nevada Sunday night and into Monday. Moisture and a potent upper
low will then eventually reach the central Rockies late Monday. WPC probabilities depict moderate-to-high chances (50-80%) for
snowfall >8" at elevations above 7,000ft in the Sierra Nevada
through Monday morning. Similar moderate-to-high chance
probabilities for >6" of snowfall exist along the ridges of
central Nevada through Monday evening.

...Northern & Central Rockies to the Central Plains...
Day 3...

The upper low responsible for the mountain snow in the mountain
ranges of California and the Great Basin will make its way into the
Central Rockies on Monday. Falling heights and residual Pacific
moisture will support moderate to locally heavy snowfall in the
Wasatch, Uinta, southern Wyoming Rockies, and northern Colorado
Rockies. WPC probabilities show moderate-to-high chances (50-80%)
for snowfall >6" at elevations above 9,000ft. Farther north,
temperatures will gradually cool as a cold front ushering in
Canadian high pressure moves south. Lingering Pacific moisture,
combined with weak easterly upslope flow will allow for light-to-
moderate snowfall in the Northern Rockies between Monday afternoon
and Tuesday morning.

There remains a fair amount of spread regarding the snow potential
in the Central and Northern Plains. The synoptic-scale jet stream
setup is generally agreed upon; a strong jet streak over northern
Mexico will place its divergent left-exit region over the central
Plains Monday night. Along with strong PVA ahead of the 500mb low
in the Rockies will result in cyclogenesis in lee of the Colorado
Rockies that will organize and strengthen a surface low rather
quickly by Tuesday. Where guidance differs are on the storm track,
the rate at which the storm deepens, and the extent to which the
colder air to the north is in place soon enough to result in a
swath of heavy snow in the Northern Plains. The GEFS members are
generally are a little faster, farther north, and deeper with the
storm by 12Z Tuesday compared to the ECENS which is slower and
farther south. The one thing these ensembles have in common is
focusing on the Palmer Divide and over the Raton Pass with strong
enough NErly upslope flow, along with strong dynamic cooling aloft
to support heavier snowfall. Even in this case, however, any faster
storm motion could mean less snowfall, and the opposite for
heavier snow should the storm slow down. Through 18Z Tuesday, WPC
probabilities show moderate chances (40-60%) for snowfall >4" along
the Palmer Divide, but lesser chances (10-20%) along Raton Pass.

With a lack of sufficiently cold air east of the Rockies, snowfall
potential will be more directly tied to the deformation axis
placement and dynamic cooling aloft from the Denver metro on north
and east. Residents in the Central and Northern Plains will want
to monitor the forecast closely over the weekend as this is a
complex storm system whose final storm track is not resolved yet.


Mullinax




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FOUS11 KWBC 060901
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
401 AM EST Thu Mar 6 2025

Valid 12Z Thu Mar 06 2025 - 12Z Sun Mar 09 2025

...Great Lakes and Maine...
Days 1-2...

Primary surface low near the northern Ontario/Quebec border will
continue to drift northeast through today. The negatively tilted
upper trough south of this low will shift up the Mid-Atlantic coast
today with rapid surface cyclogenesis tonight over the Gulf of
Maine. LES on northeasterly flow develops tonight over the eastern
U.P. and over Upstate NY (particularly near Syracuse) where Day
1.5 snow probs for >4" are 40-60%. Wrap around snow lifts over
eastern/northern Maine late tonight/Friday morning with Day 1.5
snow probs for >4" are 40-60% over northern Maine.


...Southwest, Central Rockies across the Central Plains into the
Midwest, then Southern Rockies, and Southern Plains...
Days 1-2...

...Heavy snow bands today into Friday from Wyoming across northern
Nebraska into northern Iowa...

Mid-level low along the far northern CA coast will shift south to
southern CA through tonight before further developing over the Four
Corners Friday night and shifting east to the TX Panhandle Saturday.
Meanwhile, the leading base of the trough currently over SoCal
will eject northeast over the southern Rockies by this afternoon,
across the central Plains tonight before weakening as it approaches
Chicago Friday.

Strengthening SWly jet ahead of the leading trough will allow for
quick ejection and rapid lee-side cyclogenesis over eastern CO/KS
this afternoon through tonight. Rapid banding of precip north of
this low will spread north over much of WY this morning, then shift
east over northern Neb tonight, persisting, but in a weakened state
over IA Friday. Snow totals have increased through this swath with
Day 1 snow probs for >8" over 80% in central WY terrain and 40-70%
over northern Neb. Ample Pacific moisture ahead of this wave will
keep snow levels over the Great Basin and Four Corners 4000-7000 ft
today, but will fall under the upper trough to 3000-4000ft. Day 1
WPC probabilities are high (>70%) for >8" across the terrain of
eastern NV, the Wasatch, Uintas, Wind Rivers, western CO ranges and
the highest terrain along the Mogollon Rim. Day 1 snow probs are
also high for >6" in the SoCal peninsular ranges.

SW of this secondary low, the pivoting upper low moving across the
Four Corners will drive another area of pronounced ascent leading
to periods of moderate to heavy snow across the Desert Southwest
and extending east through the TX/OK Panhandles. The column across
this region is modestly cold enough to support snow, with snow
levels around 5000-7000 ft, but steep lapse rates aloft beneath
the low will help cause strong lift to dynamically cool the
column. This suggests a mixture of rain and snow, becoming all snow
near the surface at times of heavier precipitation rates and in
terrain. Day 2.5 WPC for >6" are 40-80% over the southern Sangre
De Cristos with >4" probs 20-60% east of terrain such as the Raton
Mesa.


Jackson



$$
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FOUS11 KWBC 070855
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
355 AM EST Fri Mar 7 2025

Valid 12Z Fri Mar 07 2025 - 12Z Mon Mar 10 2025

...New York/New England...
Days 1-3...

Negatively tilted longwave trough over New England will lift north
over the Canadian Maritimes today as the surface low continues to
develop on its transit of the Gulf of St. Lawrence. Heavy snow on
the back side of this surface low under the upper trough will
continue over eastern/northern Maine this morning where Day 1 PWPF
for >6" is 50-80%.

WNW flow off Lake Ontario will continue to allow lake effect snow
(LES) over Upstate NY today with upslope snow over the Adirondacks,
northern Greens, and Whites. Day 1 PWPF for >4" are 20-40% over the
southern Tug Hill down through Syracuse and Utica as well as over
the Presidential Range in NH (which are repeated for Day 2 on
continued upslope flow).

A northern Alberta Clipper tracks over Ontario on Sunday, reaching
northern NY/New England Sunday night. Day 3 PWPF for >4" is around
20% for the northwest facing Adirondacks.


...Central Plains through the Midwest to the North-Central Appalachians...
Day 1...

The leading shortwave trough from Low pressure over the West is now
over northeast CO and will eject east through the Midwest today on
a strengthening WSWly jet. Robust, but narrow banding continues
across northern Neb/IA early this morning, and shifts east over
Chicago this afternoon. However, the wave is being sheared and the
surface low is filling, so the banding intensity should continue to
wane as it tracks east. Sufficient overlap of synoptic ascent
through the left-exit of the jet streak aloft, 850-600mb
frontogenesis, and ample Gulf-sourced moisture will continue to
drive the snow bands that should see rates drop to moderate by
mid-morning. PWPF for additional snow >2" after 12Z are 30-60% from
northeast Neb across north-central IA and along the IL/WI border.
Snow tonight reaches western PA and the central Appalachians where
there are 20-40% PWPF for >2".


...Four Corners States through Oklahoma/Texas Panhandles...
Days 1-2...

A closed low over over the southern CA border is at the base of the
still positively-tilted trough over the West. This low tracks over
southern AZ today and NM tonight before moving over the TX
Panhandle on Saturday. Further reinforcing troughs will slow the
progress east and prolong the snow fall over AZ terrain today and
the southern Rockies onto the southern High Plains tonight into
Saturday. Snow levels hover in the 4000-5000 ft range over the
Southwest, but start around 6000ft this evening over the I-25
corridor near the CO/NM border/Raton Mesa. Day 1 PWPF for >8" are
50-90% along the Mogollon Rim/White Mtns, and over the southern San Juans/Sangre de Cristos including the Raton Mesa.

Decent dynamics make for snow levels around 3500ft in the TX
Panhandle in banding on the north side of the sfc low. Snow
probabilities have risen here with Day 1.5 PWPF for >4" 40-70%
over the TX/OK Panhandles and over 80% in northeast NM.


...Western Washington...
Days 2-3...

A hearty plume of Pacific moisture tracks into western WA ahead of
the next low dropping south from the Gulf of Alaska Saturday
through Sunday night. Snow levels are generally around 4000ft
through Sunday in the WA Cascades before dropping to 2000ft Sunday
night under the trough axis. Day 2.5 PWPF for >6" is limited to the
highest Olympics/northern WA Cascades, but the Day 3 drops down to
pass level with greater coverage of >40% probabilities.


Jackson

$$
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FOUS11 KWBC 080840
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
340 AM EST Sat Mar 8 2025

Valid 12Z Sat Mar 08 2025 - 12Z Tue Mar 11 2025

...Southern Rockies through Oklahoma/Texas Panhandles into western
Oklahoma... Day 1...

Closed low over AZ/NM border will slowly fill as it shifts east to
northwest TX today and along the Red River tonight. A strong SWly
jet streak persists over west TX today, aiding ascent as the
associated surface trough shifts east. This deep layer lift and
increasing moisture will result in expanding precip over N Texas
and OK through this afternoon with an axis of moderate to heavy
precipitation across the TX Panhandle through central OK. Height
falls under the upper low and dynamic cooling in the banding should
allow snow to fall/accumulate over the TX Panhandle into western
OK this afternoon. 00Z HREF mean snow rates are generally not that
high, up to 0.75"/hr, though diurnal effects are probably causing
some of the limitation. Generally speaking, if snow bands become
strong/heavy enough they can overcome diurnal effects and
accumulate. Day 1 PWPF for >4" is 40-60% across the central TX
Panhandle, particularly along the I-40 corridor. Some probabilities
for >2" extend east into OK, but really it comes down to the
banding. The NAMnest likely remains too heavy/snowy, but the recent
HRRRs have trended a bit colder/snowier and a blend of these two
models is probably a decent approach.


...Washington to northwest Montana...
Days 2-3...

A deepening trough from low pressure over the Gulf of Alaska will
interact with a building ridge across the Desert Southwest to
funnel strengthening S/SW flow into western WA tonight, expanding
east to the northern Rockies through Monday. A weak shortwave and
accompanying vorticity lobe will swing onshore Sunday evening, and
along with the right entrance of a jet streak over Canada, enhance
lift. This will result in increasing wintry precipitation over the
WA Cascades and Olympics, pivoting into the Northern Rockies Sunday
night. Snow levels on the WA Cascades will generally be around
4000 ft during the heaviest precipitation, but will crash to as low
as 1500 ft just before precip ends Monday morning. This combined
with the transient nature of forcing suggests most of the impactful
snow will remain above pass levels, but Day 2 WPC probabilities
for >6" are 70-90% in the WA Cascades, with Day 2.5 probs 30-60%
for the Lewis Range in Glacier NP.


The probability of significant icing is less than 10 percent.


Jackson


$$
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FOUS11 KWBC 090846
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
446 AM EDT Sun Mar 9 2025

Valid 12Z Sun Mar 09 2025 - 12Z Wed Mar 12 2025


...Upstate New York and Northern New England...
Day 1...

A clipper currently crossing into Ontario will track across
northern New England late tonight. Some Great Lake moisture will be
present in the otherwise continental airmass. Upslope flow onto the
Adirondacks and northern Greens/Whites will lead to snow tonight
with potential for 0.5"/hr snow rates per the 00Z HREF. Given a
weaker clipper will cross this morning, snow from both has Day 1
PWPF for >6" of 30-70% in the highest terrain.


...Washington State to Northwest Montana...
Day 1...

Northern stream shortwave trough crosses WA this evening and
northern MT late tonight. The transitive nature of the trough
combined with modest available moisture will limit total
precipitation, but heavy snow accumulations are still likely above
4000-5000 ft. Day 1 WPC snow probabilities are above 70% for 6+
inches in the higher northern WA Cascades, generally above pass
level, and 30-60% in the higher ridges around Glacier NP. Precip
from this trough quickly cuts off Monday morning across the
Northwest.


...Northwest and California...
Day 3...

A much stronger trough amplifies as it digs off the West Coast
Tuesday night. Enhanced moisture and height falls from the
approaching trough allow moderate precip to cross the PacNW coast
Tuesday night. Snow levels at onset will be near 3500ft in WA,
4500ft in OR, and 5000ft in CA, dropping thereafter through
Wednesday ahead of the trough axis. Particularly heavy snow is
expected in California in noted by Key Messages found on the wpc
website. Further information can also be found in the medium range
discussion (PMDEPD) and from local WFO products.

The probability of significant icing is less than 10 percent.

Jackson

$$
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FOUS11 KWBC 110849
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
449 AM EDT Tue Mar 11 2025

Valid 12Z Tue Mar 11 2025 - 12Z Fri Mar 14 2025


...The West...
Days 1-3...

...Impactful heavy snow for most California mountain ranges
Wednesday into Thursday, then mostly the southern Intermountain
West and Rockies late week. Please see current Key Messages linked
below...

A strong northern stream trough currently rounding a cold-core low
over the Gulf of Alaska will further strengthen as it dives south
off the West Coast through Wednesday. The base of the trough
continues to dig south from the Central to Southern California
Coasts Thursday before ejecting east over the Four Corners Thursday
night and re-developing into a deep low over the south-central
Plains Friday.

Mountain snow begins tonight as moisture streams in ahead of the
trough axis along the length of the Cascade Range through the
Siskiyou/Shasta and northern Sierra Nevada. Day 1 snow
probabilities for >6" are 30-70% in the WA Cascades which will
expand and increase for Day 2 as snow rates increase to moderate
and snow levels drop below many Cascades passes.

This moisture surge shifts inland over CA Wednesday through
Wednesday night with the now heavy precipitation axis shifting
south with the base of the trough with snow levels generally 5000
to 6000ft at the onset of heavy snow. Height falls from the
approaching trough axis allow snow levels to drop Wednesday
afternoon through night along the Sierra Nevada with heavy snow as
low as 4,500ft in elevation before rates decrease (as low levels
further drop). The cooling column and ample moisture should result
in extreme hourly snowfall rates of 2-4"/hr in these ranges. The
combination of heavy/wet snow and increasing winds also posing a
potential risk for scattered areas of power outages and tree
damage. Day 2 snow probabilities for >18" are 50-99% in the
Shasta/Siskiyou and along the length of the higher Sierra Nevada.
1 to 4ft can generally be expected above about 6000ft.

Heavy snow will also reach the Transverse Ranges in Southern
California Wednesday night through Thursday morning with snow
levels dropping from around 6000 to 4000ft. Day 2.5 WPC snow
probabilities are 50-90% for the higher San Gabriel and San
Bernardino Ranges. 00Z Wed

East of the Pacific Mountain ranges, the expansive swath of
Pacific moisture will expand well inland Wednesday night through
Thursday night. The heaviest inland snowfall is likely to occur on
Thursday as the powerful cold front sweeps across Nevada, Utah, and
northern Arizona before shifting across Colorado and New Mexico
Thursday night. Day 3 snow probabilities for >8" are 40-80% over
the central and southern NV ranges, much of Utah terrain, the
Kaibab Plateau north of the Grand Canyon, along the Mogollon Rim to
the White Mtns of AZ, and the San Juans of southwest CO. This low
rapidly re-develops Friday over the south-central Plains.

The next wave quickly shifts toward the OR/CA border Thursday night
on a powerful NWly jet. Further info on the redeveloping low over
the Plains and the next wave into the West Coast can be found in
the WPC medium range discussion (PMDEPD), and from local WFOs.


The probability of significant icing is less than 10 percent.

Jackson


...Winter Storm Key Messages are in effect and linked below...

https://www.wpc.ncep.noaa.gov/key_messages/LatestKeyMessage_1.png

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FOUS11 KWBC 220720
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
320 AM EDT Sat Mar 22 2025

Valid 12Z Sat Mar 22 2025 - 12Z Tue Mar 25 2025


...Pacific/Interior Northwest to Central Rockies...
Days 1-3...

Shortwave over eastern WA this morning will continue east-
southeastward today across the Rockies. Light snow via onshore flow
will continue over the Cascades while light to modest snows are
expected for northwestern MT/northern ID into WY and northern UT/CO
before ending from NW to SE this afternoon and evening. WPC
probabilities for at least 6 inches of additional snow are >50%
above 5000ft (north) to 8000-10,000ft (south). The next system into
the PacNW D2 will be much milder due to increasing mid-level
ridging with snow levels rising from 4000-5000ft late tonight to
over 8000ft Sunday evening. Any initial snow over the passes will
change over to rain with significant snow at the highest peaks. By
D3, upper ridging will remain in control with light snow for the
high elevations as snow levels settle to between 7000-9000ft.


...Upper Midwest/Great Lakes/Northeast...
Days 1-3...

The upper-level trough exiting the Northern Rockies/western High
Plains this afternoon will push into the Upper Midwest tonight into
early Sunday. Multiple vort maxima will lie beneath the poleward
exit region of the modest jet over MO, providing broad vertical
ascent aloft from the Dakotas to Minnesota. Surface low pressure
over South Dakota will deepen and move into MN, with WAA driving
snow (and some mixed precip/light icing) to its northeast (MN into
WI). On Sunday, sharpening upper pattern will and a slight negative
tilt aloft will help increase snow on the NW side of the low in a
modest but still progressive deformation axis. Wraparound snow amid
dynamic cooling and low-level convergence/enhancement on the west
side of Lake Superior will help to maximize snowfall there, from
near/northeast of Duluth northeastward to Grande Portage. A modest
snowfall is expected elsewhere from central MN across northern WI
and into the U.P. of Michigan near and to the north of the track of
the sfc low pressure (and north of any subsequent secondary low
pressure development out of the Corn Belt).

By late Sunday into early Monday, frontal boundary will continue
to arc eastward, pushing precipitation across the Appalachians into northeastern PA and into NYS, where cold surface temperatures may
support some snow and light icing as WAA invades from the
southwest. Limited cold air will confine most snowfall to areas
north of I-90, but with a sfc low track remaining in Canada, many
areas may change over to rain except for northern NH into
northwestern Maine. Back to the west, colder air across the Great
Lakes will spur some lake-effect snow into the U.P. and western
Lower Michigan as 850 temps briefly drop to -10C or so. The entire
system will wind down late Monday with only some lingering lake-
effect snow by early Tuesday.

WPC probabilities for at least 4 inches of snow through the period
are highest (>70%) over northeastern MN and especially over the
eastern Arrowhead (where probabilities for at least 8 inches of
snow are >50%), northern WI and the entire U.P. of Michigan,
northwestern Lower MI, and into the Tug Hill Plateau.


For days 1-3, the probability of significant icing of at least
0.10" is less than 10 percent across the CONUS.


Fracasso

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FOUS11 KWBC 160723
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
323 AM EDT Sun Mar 16 2025

Valid 12Z Sun Mar 16 2025 - 12Z Wed Mar 19 2025

...Great Lakes... Day 1...

Guidance continues to intensify secondary low pressure developing
across the Ohio Valley early this morning downstream of a potent
shortwave trough emerging from the MS VLY. The resulting
intensification of this surface low is partly due to more
impressive downstream ridging interacting with the shortwave as it
develops a negative tilt over MO/IL/IN. Height falls and the LFQ of
an almost due-north advecting jet streak will help lower surface
pressures, and the the surface low is progged to deepen rapidly as
it lifts across the L.P. of MI and into Ontario province.

Moisture downstream of this surface low will be impressive, with
isentropic ascent lifting north from the Gulf surging PWs to above
the 99th percentile across the Mid-Atlantic, with the increasing
cyclonic flow pushing the accompanying theta-e ridge westward into
Michigan as a modest TROWAL. The overlap of this TROWAL with an
intensifying deformation axis will result in impressive omega,
partially driven by an intersection of fgen into the DGZ, to cause
rapid cooling of the column and resultant heavy snowfall. The
system is progressive off to the northeast, so the duration of
heavy snow is likely to be limited, but both the HREF and WPC
prototype snowband tool indicate a corridor of 1+"/hr snowfall
rates across the western L.P. for the first 6-10 hours of the
forecast. While the intensity has gotten stronger with recent model
runs, the placement has been quite consistent, and despite
antecedent conditions that are not favorable for snow
accumulations, these intense rates should still result in several
inches of snowfall as reflected by WPC probabilities for 2+ inches
that range from 10-30% near Chicago, IL, to above 70% near Traverse
City, MI, with 4-6" possible in the vicinity of the latter.

...The West... Days 1-3...

The period begins with the Pacific Coast sandwiched between an
anomalous ridge to the east across the Intermountain West, and an
amplifying trough well to the west over the Pacific Ocean. Between
these two features, pinched mid-level flow will surge moisture
eastward into the Pacific Northwest, with IVT progged to approach
750 kg/m/s, funneling along a cold front and focused into OR. As
the upstream trough over the Pacific deepens and pivots eastward,
it will shed periodic lobes of vorticity into the Northwest, with
an accompanying surface low likely moving towards the OR/CA
border at the start of D2 /12Z Monday/. This surface low will
briefly intensify ascent (which will already be impressive through
height falls, PVA, upslope flow, and LFQ jet-level diffluence),
while also pushing the strongest moisture channel southward into
CA. While this suggests the highest PW anomalies will pivot south
as well towards the Sierra, sufficient upper level flow will
maintain elevated moisture well inland through D2, providing the
impetus for continued moderate to heavy snowfall across the terrain as
far east as the NW WY ranges.

For D1, the heaviest snowfall is likely within the plume of highest
IVT along the cold front from the OR Cascades eastward into the
Salmon River/Sawtooth ranges, and south into northern CA and the
Sierra. Here, WPC probabilities are high (>70%) for more than 8
inches of snow, with locally 2-3 feet possible in the Cascades and
near the Shasta/Trinity region, although snow-levels indicate the
heaviest accumulations will remain above 5000 ft before falling in
tandem with weakening snow intensity. During D2, the heaviest snow
becomes primarily focused in the Sierra where a high risk (>70%)
is progged by WPC probabilities for more than 12 inches, leading to
2-day snowfall as much as 2-4 feet in the higher elevations above
4000 ft. This will still result in significantly impacted travel
across the Sierra passes Monday into Tuesday.

Most of the forcing and moisture advect east by D3, so heavy snow
should wane across much of the West as it focuses instead into the
Central Rockies, but additional snowfall of a few inches is
possible (10-30%) in the Wasatch and Northern Rockies.

...Central Rockies to the Central Plains... Days 2-3...

The next in this impressive series of significant low pressure
systems to impact the Plains will develop late Monday in the
Central Rockies and then strengthen into the Central Plains Tuesday.

This system will initially develop downstream of a large trough
which will cross out of CA and the Great Basin, reaching the Four
Corners states Tuesday morning. Downstream height falls and PVA
will help drive large scale ascent into the region, which will be
additionally enhanced by a subtropical jet streak strengthening
through the primary trough axis. As this jet streak pivots
poleward, the LFQ will overlap with the mid-level height falls to
help drive surface pressure falls, and lee cyclogenesis the latter
portion of D2 /after 00Z Tuesday/. However, this jet streak will
outrun the primary forcing in response to vorticity shedding
rapidly to the east, with secondary troughing and a more
pronounced, negatively tilted, trough developing over the Central
High Plains later Tuesday. This will result in secondary jet streak development, with even more impressive diffluence overlapping the
more structured height falls/mid-level divergence. It is this
secondary development around 00Z Wednesday that will potentially
become a powerful cyclone with heavy snow across the Central Plains
and into the Upper Midwest by the end of the forecast period.

Although the first low is weaker, it will interact with a cold
front dropping out of the interior Northwest, leading to some
enhanced ascent through fgen and upslope flow across Wyoming on D2.
Moisture streaming into the wave from the E/SE, as well as aloft
from the S/SW will manifest as precipitation across WY, but with
the heaviest snowfall likely occurring in the terrain of the Big
Horns, NW WY ranges, and along the axis of greatest fgen over
N-central WY D2. However, total snowfall is expected to be modest
this period except above 4000 ft in the NW WY ranges and Big Horns,
where WPC probabilities for 6+ inches are above 70%.

Then during D3, snowfall becomes much more expansive and heavy as
the secondary, stronger, low develops and spreads snow from the
Central Rockies into the Central Plains. There is still
considerable placement and intensity uncertainty as reflected by
broad spread in the D3-D4 clusters, but the GFS members appear to
be the deepest and fastest solutions, with the CMC/ECMWF ensembles
supporting slightly less spread and are favored at this time. With
significant spread still in place, WPC probabilities are somewhat
compromised, but still support a high risk (>70%) of 6+ inches from
the Wind Rivers through the Laramie Range and into much of the CO
Rockies where heavy snow rates are likely both through
fgen/upslope flow. Farther east, increasing deformation over the
Central Plains by the end of the period will result in increasing
coverage of heavy snowfall, and while current WPC probabilities for
4+ inches are only around 10% across NE/KS, these will likely
increase and spread northeast into D4.

Additionally, as this secondary low intensifies, the pressure
gradient is progged to become quite intense, regardless of the
model preference, and WSSI-P is already featuring a widespread
30-50% probability of moderate blowing snow impacts, suggesting
the potential for near-blizzard conditions in some areas, but those
details still need to be ironed out as the event approaches.

Weiss

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FOUS11 KWBC 230705
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
305 AM EDT Sun Mar 23 2025

Valid 12Z Sun Mar 23 2025 - 12Z Wed Mar 26 2025


...Pacific/Interior Northwest to Central Rockies...
Days 1-2...

Upper ridging just off the Pac NW coast this morning will continue
to build into the region, pushing snow levels that are around
3500-5000ft at 12Z to well over 6000-8000ft by 00Z over the
Cascades. Farther east over northern ID into MT, snow levels will
still rise today confining much of the accumulating snow to levels
above 5000ft (>6 inch amounts). Into Monday (D2), moisture will
persist into WA and the northern Rockies but with very high snow
levels above 8000ft. Heights will build into Tuesday, essentially
ending any precipitation in the Northwest altogether.

...Upper Midwest/Great Lakes/Northeast...
Days 1-3...

Mid-level shortwave over the Dakotas this morning will move
eastward today into the Upper Midwest as it surface low pressure
center follows suit across central MN into northern WI. By this
evening, the triple point low will start to become the dominant
center (near Green Bay) and move eastward across northern Lower
Michigan and then into southern Ontario as the cold front bows out
through the Northeast early Monday. With an amplifying upper
pattern, this will slow the progression of the system out of the
region, allowing cyclonic flow to persist over the Great Lakes into
the Northeast into Tuesday, favoring lake-effect snow with 850
temperatures < -10C. Though fairly progressive to start, the system
will still yield significant snow for portions of the eastern
Arrowhead and into the U.P. of Michigan via wraparound/convergent
snow in the deformation band on the NW side of the sfc low, WAA-
driven snow ahead of the sfc low (northern WI into the U.P.), or
both over northern/northwester Lower Michigan via the triple point
low. Over the Northeast, south of the eventual track of the surface
low, WAA will drive much of the precipitation on Monday with some
icing at the onset in colder areas turning over to rain and snow
farther north toward the Canadian border where it will take longer
to warm up toward freezing -- and some areas will not as a result
of a new triple point low over the Gulf of Maine, acting to hold
colder air in over northern NH and northwestern ME. Finally, some
lake effect snow will affect the Tug Hill Plateau Tuesday with
lighter upslope snow to the south into the central Appalachians.
Snowfall will finally wind down by early Wednesday (end of this
forecast period).

For the three-day period, WPC probabilities of at least 4 inches
of snow are highest (>50%) over northeastern MN, northern WI, the
U.P. of Michigan, northern/northwestern Lower MI, and in the Tug
Hill Plateau region including some of the Adirondacks. Some areas
of the White Mountains may see in excess of 4 inches of snow as
well. The heaviest snow may fall over far northeastern MN where
local convergence off Lake Superior will add to the snow efficiency
(in addition to higher SLRs in the colder air). There, WPC
probabilities of at least 8 inches of snow are > 70%.


For days 1-3, the probability of significant icing of at least
0.10" is less than 10 percent across the CONUS.


Fracasso


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FOUS11 KWBC 240653
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
253 AM EDT Mon Mar 24 2025

Valid 12Z Mon Mar 24 2025 - 12Z Thu Mar 27 2025


...Pacific/Interior Northwest to Northern Rockies...
Day 1...

Lingering moisture over the Northwest and northern Rockies atop
the upper ridge will slowly dissipate today, with very high snow
levels around 8000ft.


...West Coast...
Day 3...

Next Pacific system will start to bring in some moisture to
western WA/OR and NorCal. Snow levels will still be quite high --
10,000ft on Wednesday -- but dropping to around 5000ft by 12Z
Thursday, which still start to bring snow to some passes.


...Great Lakes/Northeast...
Days 1-2...

Mature winter storm over the Great Lakes this morning will
continue eastward through southern Ontario as a new triple point
low develops near the NY Bight this afternoon. Cold air at the
surface this morning will be slow to erode over the higher
elevations (Catskills, Berkshires/Greens, Worcester Hills, and
parts of Maine) as WAA-driven precip arrives this morning, favoring
some freezing rain amid a snow-to-rain changeover for areas south
of I-90. As the coastal low deepens, it will tend to hold in colder
air over northern New England and much of Maine, with marginal
temperatures toward the coast. This will make for a heavy/wet snow
of a few inches in NH to several inches over interior Maine as the
low pressure moves through the Gulf of Maine this evening. Snow
will end overnight associated with the area of low pressure, but
the large cyclonic circulation over the Great Lakes will sustain
some lake-effect snow today into Tuesday, especially over the
northern U.P. of Michigan, northwestern Lower Michigan, and into
the Tug Hill Plateau. WPC probabilities for at least 4 inches of
snow are >50% over the aforementioned lake-favored areas as well as
over northern NH (White Mountains) into Maine north of I-95 until
Bangor, then along 95 to the Canadian border.


...New England...
Day 3...

Vort max moving through the base of the upper trough over the
Great Lakes on Tuesday will move off the Mid-Atlantic coast and
turn the corner northeastward early Wednesday. Models have wavered
on how close to bring this system to eastern New England, but at
least some light precipitation is likely to affect at least areas
east of I-91. With marginal to somewhat sufficient cold air in
place, some light snow is likely for eastern New England before the
system races northeastward into Atlantic Canada Wednesday evening.
Some of the models were much more vigorous than others, but the
probability of at least 4 inches is still low (10-30%) from
northern NH into Maine.


For days 1-3, the probability of significant icing of at least
0.10" is less than 10 percent across the CONUS.


Fracasso


$$
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FOUS11 KWBC 250644
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
244 AM EDT Tue Mar 25 2025

Valid 12Z Tue Mar 25 2025 - 12Z Fri Mar 28 2025


...Great Lakes/Northeast...
Days 1-2...

In the wake of the departing system just leaving the Northeast
this morning, broad cyclonic flow centered south of Hudson Bay will
maintain a cold flow of air over the slowly warming Great Lakes,
promoting some lake effect snow for the next couple of days. The
most favored areas will be across portions of the eastern U.P. of
Michigan in any more organized/persistent bands, east of Lake
Ontario along the long fetch of the lake (Tug Hill Plateau), and
into the Green Mountains via upslope enhancement. Two-day totals
will be generally light (1-3") but the aforementioned areas show
the highest probabilities of seeing at least 4 inches of snow
(10-70%, with the highest probabilities of at least 6 inches over
the Tug Hill).


...West Coast...
Days 2-3...

An anomalously deep and impressively wound-up system in the
northeast Pacific late Tue into Wed will start to field moisture
into the West Coast starting Wednesday afternoon. Strong ridging
over the West means snow levels will start very high (>8000ft)
during the middle of day 2 (00Z Thu) but will trend lower into day
3. Then (12Z Thu - 12Z Fri) the upper/sfc low will curl
northeastward to northward to a position just offshore Vancouver
Island, allowing its long occluded front to push inland. This will
take snow levels down to about 5000ft by 12Z Fri over the Cascades
into the far northern NorCal ranges and about 6000-7000ft over the
northern Sierra as a 130kt jet streak moves through. QPF amounts
will be light to modest inland with heavier amounts along the coast
and into the Olympics in WA. Rain will change to snow with low
SLRs and will come in a couple waves -- initially with the front in
the higher PW plume and then with the upper trough. Snow will
accumulate the most at the highest peaks but eventually will get to
some high passes in northern CA. Through 12Z Fri, WPC
probabilities for at least 8 inches of snow are highest (>50%) in
the Olympics, Cascades, and NorCal ranges (Shasta Siskiyous,
Trinity, Klamath, etc.) above 5000ft.


For days 1-3, the probability of significant icing of at least
0.10" is less than 10 percent across the CONUS.


Fracasso


$$
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FOUS11 KWBC 260636
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
236 AM EDT Wed Mar 26 2025

Valid 12Z Wed Mar 26 2025 - 12Z Sat Mar 29 2025


...Northeast...
Day 1...

Compact upper low over southwestern Ontario this morning will move
across northern NY/VT midday and through Maine this evening. This
will spur some more light snow into the Tug Hill Plateau where 1-3"
is likely. Farther east, low probabilities (10-30%) are shown for
more than 4 inches of snow over the Green and White mountains via
upslope enhancement as the feature moves through.



...Upper Midwest/Great Lakes/Northeast...
Days 2-3...

Flattening upper ridging exiting the High Plains Thursday combined
with lee-side surface cyclogenesis centered over South Dakota
Thursday night will favor broad WAA-driven precipitation along and
north of a surface boundary astride the Upper Midwest into the
Great Lakes. With the fast zonal/progressive flow, this will
quickly expand eastward through Canada and into the Northeast with
an influx of moisture from the southwest, reaching into NY Fri
evening then into New England overnight into early Saturday.
Temperatures are marginal for most areas, confining wintry
precipitation to areas closer to the Canadian border. However, that sub-freezing surface layer will be overrun from the S/SW with
warmer air aloft, promoting a rather large area of sleet/freezing
rain from northern MN eastward across the U.P. of Michigan and
northern WI across Ontario and into the Adirondacks. Ptype from the
models (and NBM) show a strong signal for freezing rain
(impressive for late March), but this may be modulated my afternoon
insolation. Nevertheless, WPC probabilities for at least 0.10"
icing are moderate (30-70%) over northeastern MN, the U.P./northern
WI, and the northern part of Lower Michigan. Snow amounts may be
limited, with the highest amounts of a couple inches over northern
MN where WPC probabilities for at least 4 inches are barely 10%.


...Cascades into the northern Sierra Nevada...
Days 2-3...

An anomalously deep, cold core low in the northeast Pacific will
curl up toward Vancouver Island as its wound up occlude front moves
inland tonight. High snow levels (>8000ft) this afternoon will
steadily drop to around 4000-5000ft tomorrow, then to around 4000ft
Friday with the passage of the upper trough. Snow will eventually
get to some of the passes but much of this will fall over the
higher terrain. Two-day probabilities of at least 8 inches of snow
are highest above 5000ft or so along the Cascades southward to the
NorCal ranges and northern Sierra. Moisture will continue inland to
the northern Rockies with a few to several inches of snow for the
Blue Mountains and into SW MT as a frontal boundary in the area
acts as another focus for forcing. There, WPC probabilities for at
least 8 inches of snow are low (10-30%).


Fracasso


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FOUS11 KWBC 200657
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
257 AM EDT Thu Mar 20 2025

Valid 12Z Thu Mar 20 2025 - 12Z Sun Mar 23 2025


...Pacific and Interior Northwest...
Days 1-3...

Progressive pattern out of the North Pacific will maintain an
unsettled period for the Pacific Northwest into the northern
Rockies. Initial front has moved past the Cascades as of early this
morning and will continue eastward across the Divide later today.
Next system will be forced by a modestly strong incoming jet
(130kts) tonight with westerly flow focusing into the Cascades,
followed by height falls from the northwest (southwestern Canada)
late Fri into early Sat. That system will dig much farther west out
ahead of incoming ridging into WA/OR, finally setting up some
drier periods on Saturday.

Low snow levels in the Cascades of around 2000-3000ft this morning
will rise through the day and overnight to around 3500-4500ft
(north to south) coincident with the next surge of moisture. Snow
levels will fall again late Fri into early Sat as the Canadian
height falls push into WA then into northern ID, down to around
1500-3000ft from north to south as the precipitation gradually
ends.

Three-day totals of at least 12 inches of snow are likely (>70%
chance) above 3500-4500ft or so from north to south along the
Cascades with some higher elevations receiving more than 2-3 ft.
Significant snow is also possible at many passes given the lower
snow levels. There is a >60% chance of at least 8 inches of snow
above 2500-3000ft or so. Farther east, significant snow in excess
of 12 inches is likely (>70% chance) across the Blue Mountains, central/northern Idaho, northwestern Montana, and into western
Wyoming. The southern extent of the snow will clip northern Utah
and the CO Rockies as well with light/modest amounts near 6 inches
(UT) and nearing 12 inches into CO, especially above 10,000ft.


...Upper Midwest...
Day 3...

The system exiting the High Plains late Sat will continue to dig
into the northern Plains overnight into early Sun. Low pressure
will coalesce over eastern SD Saturday evening and lift into MN
thereafter, bringing WAA-driven snow to northeastern MN, northern
WI, and the western U.P. of Michigan. Amounts will generally be
light through 12Z Sun, perhaps 1-2.5", and the probability of at
least 4 inches is less than 10%. Additional accumulation is likely
beyond this forecast period.


...Great Lakes/Appalachians/Northeast...
Days 1-2...

Exiting system responsible for blizzard conditions over the
central Plains will move into Canada with snow ending over Michigan
this afternoon. Additional snow accumulations will be light (an
inch or so). To the south, colder air will change rain to snow over
the central/southern Appalachians with upslope-driven
accumulations persisting into early Friday. Several inches of snow
are possible at the higher elevations above 3500ft, but WPC
probabilities for at least 4 inches are low (10-40%) along the
TN/NC border. By day 2, low pressure over Cape Cod early Fri will
lift into Nova Scotia with backside snow over northern New England,
but mostly at higher elevations above 2500ft and amounts will
generally be light (<3 inches). The highest peaks of the White
mountains may see more than 4 inches (probabilities generally
10-50%).


For days 1-3, the probability of significant icing of at least
0.10" is less than 10 percent across the CONUS.


Fracasso

$$
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FOUS11 KWBC 270713
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
313 AM EDT Thu Mar 27 2025

Valid 12Z Thu Mar 27 2025 - 12Z Sun Mar 30 2025


...West Coast through Northern/Central Rockies...
Days 1-3...

An anomalously deep, cold-core low off OR near 135W will further
occlude and curl up toward Vancouver Island through Thursday night
with the occluded front crossing the West Coast this morning. Snow
levels continue to rapidly drop to around 4000-5000ft today across
the Cascades into the northern CA ranges, then to around 3500ft
Friday with the passage of the upper trough axis. Accumulation
will eventually reach to some of the passes in the Cascades by
Friday, but the rates will drop around that time as well. WPC
probabilities for at least 8" of snow are high (>70%) on Days 1-2
across the high elevations of the Cascades and into the northern CA ranges/northern Sierra.

Moisture will continue inland through the northern Rockies Friday
through Saturday with periodic heavy snow above 5000ft snow levels
on Friday and 4000ft on Saturday. Snow also begins to enter the
central Rockies by Saturday as a trailing shortwave crosses the
region and drops snow levels below 7000-8000 ft. Snowfall
probabilities for at least 8" remain greatest across western MT and
towards the Little Belts and Bighorns of WY, where 50-80% values are found.


...Upper Midwest/Northern Great Lakes/Northeast...
Days 2-3...

Flattening upper ridging exiting the High Plains Thursday combined
with lee-side surface cyclogenesis centered over South Dakota
Thursday night will favor broad WAA-driven precipitation along and
north of a surface boundary draped over the Upper Midwest into the
Great Lakes. With the fast zonal/progressive flow, this will
quickly expand eastward from southern Canada and the Northeast
through the daytime on Saturday. Temperatures are marginal for
most areas, confining snow to areas closer to the MN- Canadian
border through Friday and northern NY/VT/NH into ME on Saturday.
However, this band of snow could be quite potent as the region
falls within the right entrance region of a 130 kt jet and IVT over
the 90th climatological percentile over the Great Lakes per the
NAEFS on Friday night. The narrow, but intense WAA combined with
favorable synoptic ascent and moisture could lead to snowfall rates
of 1-2"/hr, particularly across parts of New England by the end of D2.

Meanwhile, a sub- freezing surface layer will be overrun from the
S/SW with warmer air aloft, promoting a long, but narrow swath of sleet/freezing rain from the northern Plains eastward across the
U.P. of Michigan and northern WI through Ontario, the Adirondacks,
and central New England. Ptype from the models (and NBM) show a
strong signal for freezing rain (impressive for late March), but
this may be initially modulated by Friday afternoon insolation
before focusing over the U.P. of MI Friday evening. Day 2 ice
probabilities for >0.25" have risen to 30-60% over much of the U.P.
and the far northern L.P. Day 2-3 ice probabilities for >0.25"
across the Northeast are 20-40% and highest across the northern
Adirondacks as precipitation lingers through the end of Day 3 while
warmer air begins eventually lifting back north. Day 2 snow probs
for >4" have a very sharp gradient along the MN- Canadian border
with 50-70% values at the top of the Arrowhead of MN. For the
Northeast and New England on Days 2-3, probabilities for >6" have
increased to 30-50% for northern VT/NH and into central ME, with
higher values (60-80%) in the Whites of northern VT and neighboring
areas in ME.


...Northern Plains/Upper Midwest/Northern Great Lakes...
Day 3...

Quickly following the northern Great Lakes system on Day 2 a shortwave
trough axis that crosses the PacNW Friday reaches the northern
Rockies on Saturday along with a southern piece of energy crossing
the central Rockies and promotes Colorado lee- side low
development on Saturday. Broad convergence should allow some
moderate to locally heavy snow bands to form around the Black Hills
of SD (maybe far northern NE) eastward into MN by Saturday
afternoon. The 12Z GFS/EC have come into better agreement, though
the EC remains a bit farther north with the axis of heavier snow.
WPC probabilities for at least 4" of snow are 30-50% from northern
WI to the western U.P., with lower probabilities (10-30%) extending
from the Black Hills of SD through central MN. These probabilities
are likely to increase over the next few forecast cycles once
better agreement in the northern extent of QPF comes into focus. With
high pressure remaining locked in over the southern Hudson Bay,
there remains a strong signal for mixed ptype from MN through WI
and into the U.P. and northern L.P. of MI. Day 3 freezing rain
probabilities for >0.25" are currently low (10-30%) from central WI
through the northern L.P. of MI.



Snell


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FOUS11 KWBC 210713
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
313 AM EDT Fri Mar 21 2025

Valid 12Z Fri Mar 21 2025 - 12Z Mon Mar 24 2025

...Northeast...
Day 1...

Low pressure near Cape Cod this morning will move through the Gulf
of Maine and into Nova Scotia this afternoon, helping to draw in
colder air on the back side of the exiting precipitation shield.
Rain will change to snow from west to east with some light
accumulation over most areas, but the higher terrain of the White
Mountains may see a few inches. There, WPC probabilities of at
least 4 inches of snow are 10-40%. In addition, there is a
possibility of some modest snow amounts over eastern Maine outside
the higher terrain as the low deepens in the Gulf of Maine this
afternoon. Snow will end by midnight over eastern Maine.


...Pacific/Interior Northwest to Central Rockies...
Days 1-3...

Onshore flow continues in the PacNW with a due east jet off the
northeast Pacific aimed into WA/OR. Current jet max along the
Columbia River will continue eastward this morning, but another
will be right on its heels which will promote a moisture plume into
the OR/WA Cascades this afternoon/evening. Snow levels around
3000-5000 ft will still impact the passes today. Snow will lessen
into day 2 (Sat) as height falls dig into the northern Rockies,
which will continue eastward into day 3. By then, upper ridging
will move into the PacNW with a system into the southern AK
Panhandle, allowing snow levels to rise much higher to above 6000ft
Sunday afternoon into early Monday. Three-day totals of at least
12 inches of snow are likely (>70% chance) above 4000ft or so but
primarily on day 1.

West-to-east jet will continue to advance the moisture plume into
the northern Rockies, favoring the Blue, Sawtooth, Bitterroots,
Lewis Range, Absaroka, and Tetons through Saturday morning.
Elevations above 5,000ft in the Blue, Sawtooth, Bitterroots, and
Lewis Range have at least a 70% chance of receiving at least 12
inches of snow through tomorrow morning. Probabilities are a little
lower to the south (Absarokas and Tetons), but many areas will
still see at least 8 inches of snow (>70% chance above 7000ft or so).

On the south side of the jet and moisture plume, northern UT into
the CO Rockies will likely see at least 8 inches of snow above
9000ft or so (>70% chance), starting later tonight into Saturday
then ending Saturday night.


...Upper Midwest & Great Lakes...
Days 2-3...

Height falls associated with a shortwave exiting Montana Saturday
evening will continue to deepen into MN by Sunday morning in
response to the amplification of the upper pattern upstream. Low
pressure over SD will track eastward into MN with broad WAA ahead
of it over the Upper Midwest. Surface temperatures will be fairly
marginal with some areas starting as rain before mixing with and
changing to snow as the low strengthens on Sunday. As it does,
colder air will wrap around its northwest side over northern MN
moderate snow likely for a time Sunday afternoon. Models have been
wavering on the strength of the upper and sfc features (and thus
the QPF and ultimately the snow), but the eastern Arrowhead (Lake
Shore) may be in a favorable spot for heavier snow due to easterly
flow off Lake Superior. SLRs may start on the lower end below 10:1
then rise as colder air works its way in, but will also combat
afternoon solar insolation where rates are not as heavy. All told,
WPC probabilities for at least 4 inches of snow days 2-3 are at
least 10 percent generally north of I-94, with increasing
probabilities northward and northeastward into the Arrowhead. This
also includes northern WI into the U.P. of Michigan from a
combination of front-end WAA snow and wraparound snow after the low
passes through. Despite likely closing off up to 500mb, the system
will remain progressive but will not clear the area until after 12Z Mon.


For days 1-3, the probability of significant icing of at least
0.10" is less than 10 percent across the CONUS.


Fracasso


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FOUS11 KWBC 280748
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
348 AM EDT Fri Mar 28 2025

Valid 12Z Fri Mar 28 2025 - 12Z Mon Mar 31 2025

...West Coast through Northern/Central Rockies... Days 1-3...

A deep, slow-moving low centered off of the Northwest coast will
gradually fill as it lifts to the north over the next day or so.
However, even as the system lifts out, snow levels across the
Northwest will continue to drop into early Saturday as a series of
shortwave troughs digging south of the low move inland. This will
bring levels down to around 3000-4000ft in the Washington and
Oregon Cascades today, before dropping below 3000ft with the
passage of a well-defined trough Saturday morning. Further to the
south, snow levels starting above 5000ft in the Shasta- Siskiyou
region and the northern Sierra Nevada will drop below 4000ft in
many locations before precipitation ends. Although snow levels will
be on the decline, so will the onshore moisture advection, with
guidance showing IVTs dropping off after the start of the period
and a break in precipitation on Day 2. The heaviest precipitation
is expected to center across southern Oregon and far northern
California, where the best moisture and forcing is expected to
focus later today. By early Saturday, precipitation is expected to
diminish from south to north as an upper ridge moves inland in the
wake of the previously-noted trough. Day 1 WPC probabilities for
over 8 inches of snow are 60-80% for parts of the Olympics,
Cascades, Klamath Mountains, and the northern Sierra Nevada. Then,
the next system approaches the West Coast by Day 3 as the closed
upper low off the Pacific Northwest reloads from energy dropping
southward across the eastern Aleutians. This leads to additional
moderate onshore flow amid initial snow levels around 4000-5000ft
(up to 6000ft in the central/southern Sierra). WPC probabilities
for at least 8 inches of additional snow on Day 3 across the Sierra
and northern CA ranges are 40-70%, but are expected to increase as
the bulk of the precipitation moves onshore after 12z/Mon.

Meanwhile, moisture spreading inland across the northern Great
Basin and Rockies will begin to interact with a developing low-to-
mid level baroclinic zone and periods of enhanced forcing
associated with the inland moving troughs to produce light-to-
moderate precipitation, including mountain snow from the northern
to the central Rockies. Precipitation coverage is expected to
increase Friday night, with unsettled weather continuing through
the weekend and ending with a weak area of convergence on Sunday
between western MT and northern CO. Snow levels beginning above
5000ft in the northern Rockies Friday night are forecast to dip
below 4000ft in some location by late Saturday. In the central
Rockies, snow levels will drop to 7000-8000ft in the Colorado
ranges and around 5000-6000ft across northern Utah. WPC Days 1-2
probabilities for at least 8 inches of snow are generally 50-70%
from the Blue Mts of northwest OR through the central ID ranges
into southwest MT, as well as the Absarokas and Wind River Range.
These probs also extend south to the Park Range and Medicine Bow
Mountains of CO/WY.

...Northern Minnesota through the Northern Great Lakes... Day 1...

A longwave upper trough in the West working in tandem with the
right-entrance region of a 250mb jet streak this afternoon will
foster large-scale ascent aloft throughout the Upper Midwest and
Great Lakes. The upper trough and a strong low-level ridge of high
pressure off the Southeast coast supports a strengthening SWrly
low-mid level flow regime that results in exceptional warm-air
advection (WAA) for the regions reference above. This WAA will
clash with a cold Canadian air-mass anchored by a 1030mb+ high
pressure system over Ontario and Quebec. The result is 925-700mb
FGEN that produces a narrow band of disruptive snow (primarily
north of the U.S.-Canadian border) and ice starting as early as
this morning across far northern MN, but becoming more widespread
across northern MN/WI/MI by this evening. The strong WAA over sub-
freezing boundary layer temps is a favorable setup for freezing
rain/sleet that will make for hazardous travel conditions even
where only light amounts occur. WPC probabilities for at least
0.25" of ice accretion on Day 1 is medium (50-70%) across the
eastern U.P. and northern L.P. of MI, with 20-40% chances extending
westward across the U.P. and into the MN Arrowhead.

...Northeast... Days 1-3...

This same system is expected to spread a narrow swath of heavy snow
and area of mixed precipitation into the Interior Northeast and New
England by late D1, but with wintry precipitation lingering for
several days. This long-duration event made possible by a trailing
shortwave and developing central U.S. trough which will continue to
reinforce a favorable jet pattern for upper divergence as well as
sufficient mid-upper level moisture content. However, the snowfall
threat peaks early Saturday morning as a jet max passes to the
north of New England and 925-850mb WAA is at it's strongest. 00z
HREF depicts 30-40% chances for 1-2"/hr snowfall rates around
13z/Sat across far northern NY and northern VT/NH. WPC snowfall
probabilities for at least 6 inches of snow on days 1-2 are medium
(40-60%) from northern NH, VT, and into central ME.

South of this heavy snow threat between the northern Adirondacks
and much of central/southern VT and NH, 850-750mb warm nose allows
for a transition area of sleet/freezing rain. After the brief
burst of heavier precip early Sat, forcing weakens and there is
left a weak stream of moisture overrunning a CAD signature due to a
strong 1030mb High situated over the James Bay. This potentially
significant icing threat is expected to linger through Sun morning
until the surface low across the Midwest begins to strengthen and
push warmer air northward across New England by Day 3. However, the
CAD signature in place will continue to support freezing rain
across the typically colder valley locations and areas banked along
the Green/White mountains. WPC probabilities for the entire
forecast period (ending 12z/Mon) are high (70-80%) for at least
0.25" of ice accretion from the NY border with eastern Ontario
through the northern Adirondacks and into central VT/NH.
Probabilities for at least 0.5" also impressive and 40-60% (highest
across western Jefferson county of NY).

...Northern High Plains through the Upper Midwest/Great Lakes... Days 2-3...

A shortwave trough moving into the Southwest today is expected to
lift northeast from the Four Corners across the central Rockies and
into the High Plains Saturday morning. Moisture fed into an area
of strong ascent generated in part by favorable upper jet forcing
and potent 700mb closed low will support precipitation north of an
associated surface low that will develop and move east of the
Colorado Rockies. Rain changing to snow is expected from
southeastern Montana and northeastern Wyoming into parts of
western to central SD and NE. The highest amounts are forecast to
fall across the Black Hills, but locally heavy totals are also
possible eastward along southern SD and north- central NE. WPC
probabilities for at least 4 inches are 40-70% across the Black
Hills and 10-30% into south-central SD and north- central NE.

As this system develops further Saturday night through Day 3,
increasing WAA and a blossoming precipitation shield is expected to
spread into the Upper Midwest and Great Lakes. Surface low pressure
is expected to track along along the 925-850mb front that remains
stationary from NE and southern MN on east through Michigan. There
still remains some discrepancies in guidance on the evolution/strength
of this storm system, but there is a growing consensus with the
00z guidance on the synoptic scale. The GFS finally has a more
amplified solution (in line with the CMC and ECMWF), which paints
an axis of snow fall extending east-northeast from SD through
central MN into northern WI and the MI U.P.. There is also higher
confidence in yet more freezing rain/sleet from northern and
central WI on east through northern Michigan as high pressure
remains locked in place over James Bay and cold northeast flow
continues to filter into the Upper Midwest/Great Lakes. This is a
very favorable setup for potentially significant freezing rain from
northern WI through northern MI, especially for late-March. WPC
probabilities show moderate chances (30-60%) for ice accumulations

0.25" in these areas with low chances (10-30%) for >0.5" across

parts of northern WI. In terms of snowfall, WPC probabilities show
moderate chances (30-60%) for snowfall totals >6" in far northern
WI and the western MI U.P..

Snell
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FOUS11 KWBC 290823
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
423 AM EDT Sat Mar 29 2025

Valid 12Z Sat Mar 29 2025 - 12Z Tue Apr 01 2025

...Central/Northern Plains, Upper Midwest, and Northern Great Lakes...
Days 1-2...

Long-duration ice storm to impact northern WI through the northern
MI L.P. and much of the central/eastern U.P. through Sunday, while
moderate to heavy snow is likely from SD/Neb through far northern
WI and along the lakeshore of Lake Superior.

A negatively tilted upper trough will cross the Intermountain West
today and usher potent SWrly flow into the north-central U.S.,
while a leading mid-level shortwave ejects into the central Plains
by this afternoon. This leading shortwave is associated with
leeside cyclogenesis along the CO/KS border and an attached sharp
stationary front extending east-northeast through the Midwest and
Great Lakes. As moisture overruns this frontal boundary and
expansive high pressure stretches across Canada, a wintry mix of
snow, sleet, and freezing rain is likely this weekend.

Snowfall is forecast to begin across western Neb into the Black
Hills and south-central SD by this afternoon associated with the
mid-level low crossing overhead leading to sufficient convergence
and bands of snowfall capable of containing 1-2"/hr rates. These
rates will be imperative to achieving heavy accumulations as
boundary layer temperatures start out well above freezing. The 00z
HREF depicts the best chances for these intense snowfall rates are
along the western and central SD/Neb border centered near the Pine
Ridge Reservation. Snowfall rates will likely lower while the
northern precipitation shield expands east-northeast in response to
the progressing surface low and forcing becoming more stretched in
an east-west direction. Moderate snow will extend across SD,
central MN, and towards far northern WI and the MI U.P. by tonight.
There has been some latitudinal uncertainty regarding this swath
of snow, with 00z guidance coming in a touch south. Regardless, WPC probabilities for at least 4" of snow are 30-60% for this region,
with localized pockets up to 80%. Meanwhile, the heaviest snowfall
from this system is most likely from near or just south of Duluth,
MN eastward along the lakeshore of Lake Superior from far northern
WI into the MI U.P. due to snow remaining the dominant ptype
throughout the event. Here, WPC probabilities for at least 6" are
high (60-80%).

South of the heavy snow axis a corridor of impactful sleet and
freezing rain are forecast to stretch from northern WI through much
of northern MI. A prior storm has already led to a corridor of ice
across this region and precipitation may linger continuously today
across northern WI/MI until a resurgence tonight through Sunday.
High pressure (~1030mb) over James Bay will continue to usher in
cold northeasterly flow as the surface low tracks across southern
WI on Sunday. Ice accretion may be limited during daytime hours
given the late-March sun angle, but with the bulk of the wintry mix
occurring Saturday night there is the potential for significant
ice accumulations. WPC probabilities for at least 0.25" of freezing
rain are highest (60-90%) across parts of northern WI and the
northern MI L.P., with chances for >0.5" at 30-60%. Medium
probabilities (30-60%) for at least 0.25" also extend into the
central/eastern MI U.P. as well as into parts of northwestern WI to
the border of MN. In addition to the freezing rain threat, some
areas from northern WI to the MI U.P. could experience over 1" of sleet.

...Northeast... Days 1-2...

Prolonged wintry mix expected across the Interior Northeast through
New England this weekend, including the potential for heavy icing
before above freezing temperatures return on Monday.

An initial pulse of heavy precipitation is swinging through
northern NY and New England this morning, including heavy snow up
to 1"/hr until around 14Z across northern VT into central/northern
NH. This snowfall is a result of a jet max passing to the north of
New England and where 925-850mb WAA is strongest, which quickly
wanes later today.

South of this heavy snow threat between the northern Adirondacks
and much of central/southern VT and NH, 850-750mb warm nose allows
for a transition zone of sleet/freezing rain. After the brief
burst of heavier precip this morning, forcing weakens and there is
left a weak stream of moisture overrunning a CAD signature due to
the strong High situated over the James Bay and elevated PWs (above
the 90th climatological percentile per the NAEFS SAT) continuously
advected from the WSW. WAA gains latitude by Sunday as the Great
Lakes low pressure strengthens and tracks northeast into Canada by
Sunday night. Even with this storm track turning the entire northeast eventually over to rain on Monday, a prolonged wintry mix this
weekend could lead to significant freezing rain amounts. Areas most
at risk for heavy icing include northern NY and the Adirondacks,
through the Greens and Whites of VT/NH, where CAD is likely to
remain longest.

WPC probabilities for >0.25" ice are 60-80% for the Thousand
Islands area, the northern Adirondacks and south- central VT/NH.
Probabilities for >0.1" ice extend as far south as the MA
Berkshires and northward along the White Mts through ME into Day 2.

...Northern/Central Rockies... Days 1-3...

An upper trough sliding eastward across the Intermountain West
today will maintain some Pacific moisture advection into the
northern/central Rockies while also interacting with a developing
low- to- mid level baroclinic zone to produce light-to- moderate
mountain snow this weekend. Precipitation coverage is expected to
peak on Day 1 as the upper trough moves through, with unsettled
weather continuing through Sunday across MT/WY due to the
relatively strong baroclinic zone being reinforced by high
pressure positions over southern Saskatchewan. Snow levels
beginning around 5000ft in the northern Rockies are forecast to dip
below 4000ft in some location by this evening. In the central
Rockies, snow levels will drop to 7000-8000ft in the Colorado
ranges and around 5000-6000ft across northern Utah. WPC Days 1-2
probabilities for >8" of snow are generally 40-70% over southwest
MT, the Absarokas and Wind River Range, and the Park Range and
Medicine Bow Mountains of northern CO.

By the end of Day 3/12z Tuesday, a strong closed upper low returns
to off the Pacific Northwest and extends a 160kt 250mb westerly
jet inland through the central Great Basin. Pacific moisture,
upslope flow, and increasing upper divergence to the north of this
low produces the next round of mountain snow across the
northern/central Rockies. Current WPC Day 3 probabilities for at
least 8" are 30-50% from southwest MT, western WY, into the
northern CO Rockies.

...West Coast through the Intermountain West... Days 2-3...

The next cold core low drifts toward OR, but remains offshore
Sunday through Monday. A broad plume of Pacific moisture shifts
inland Sunday and lifts northeastward with renewed enhancement
from an ejecting shortwave trough Sunday night producing heavy
precip over the northern half of CA Monday. Days 2-3 snow probs for

8" are 50-90% in the southern OR Cascades, the Klamath/Trinity

Alps, and northern/central Sierra Nevada with snow levels of
5000-6000ft Sunday dropping to 4000-5000ft by Monday morning. Snow
also extends into the central/northern Great Basin Sunday night
through Monday, with snow levels falling below 4000-5000ft on Day 3
across the Idaho ranges and remaining around 5000-6000ft across UT/NV.

Snell
$$
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FOUS11 KWBC 300721
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
321 AM EDT Sun Mar 30 2025

Valid 12Z Sun Mar 30 2025 - 12Z Wed Apr 02 2025

...Upper Midwest, Northern Great Lakes, and Northeast... Day 1...

Ongoing prolonged late-season ice storm continues across portions
of northern WI into the northern MI L.P. and central/eastern U.P.,
as well as New England today. A negatively tilted 250-500mb trough
axis working in tandem with the strongly diffluent right- entrance
region of a 250mb jet streak has organized an area of low pressure
tracking across the Great Lakes today. Sufficiently cold
temperatures remain locked in place to the north of the robust
925-700mb FGEN warm front that is oriented W-E from northern WI to
as far east as New England. This is all thanks to a 1030mb+ high
pressure system over southeastern Canada that is supporting the
ongoing icy setup. As strong SWrly winds overrun the sub-freezing
air-mass, a >0C warm nose protruding into the 850-700mb will cause precipitation to fall in the form of freezing rain and sleet
throughout the Upper Midwest, Upper Great Lakes, the northern
Appalachians, and New England into the end of Day 1. By Monday
morning the low pressure system is forecast to push into southeast
Canada and surge above freezing temperatures throughout the entire
East Coast, with precipitation also gradually ending across the
Great Lakes. While ice will be the more commonly observed winter
weather hazard, there will be light to moderate snow beneath the
deformation zone on the northern and western flanks of the 850mb low.

Periods of snow will be ongoing across central MN into northern WI
and the MI U.P. this morning, as well as wrapping around the
western side of the low as far south as northwest IA. South of the
snow axis, freezing rain and sleet will be common in northern
Wisconsin, the eastern Michigan U.P., across the tip of Michigan's
Mitten, and into interior New England. The 0C surface line will
gradually lift northward throughout the day east of the low
pressure, but will be stubborn to lift across northern MI and
northern New England. The deformation axis will continue its swath
of snow from southeast Minnesota to central Wisconsin Sunday
afternoon, but it will be progressive and snow falling during the
daytime hours will be tougher to accumulate. Snow within the
deformation axis may continue over northern Michigan Monday morning
before finally exiting to the northeast over Ontario by Monday afternoon.

WPC probabilities show moderate-to-high chances (60-80%) for >6"
of snowfall for areas along the shore of Lake Superior in the MI
U.P.. In terms of freezing rain, WPC probabilities show moderate
chances (40-60%) for additional ice accumulations >0.25" in
northern Wisconsin, northern Michigan, and in the New England
mountain ranges such as the Greens and especially the Whites.
There is also an area of low chances for an additional >0.5" of
ice accumulation as far eastern MI U.P.. All of these areas can
anticipate hazardous travel conditions with the potential for
additional power outages in those areas sporting better chances
for >0.50" of total ice accumulation.

...The West... Days 1-3...

An active stretch of wintry weather is expected from the West
Coast to the Front Range of the Rockies through Monday due to
persistent troughing. A pair of shortwaves traversing the Rockies
early this morning is responsible for ongoing mountain snow from
as far north and west as the Absaroka and Bitterroots through the
Wyoming ranges and on south to the Colorado Rockies. As high
pressure builds in over the Canadian Prairies today, easterly
upslope flow and residual moisture aloft will foster additional
mountains snow in the Black Hills and Big Horns. Some lower
elevations snowfall is expected during the day on Sunday as well,
but accumulations will be minor due to the late season sun angle
limiting accumulations. WPC probabilities do depict moderate
chances (40-70%) for snowfall totals >6" in the highest elevations
of the Absaroka, Wind River, and northern Colorado Rockies.

By this afternoon, focus shifts to an exceptional closed upper low
in the northeast Pacific that slowly makes its way east towards
the Pacific Northwest by Monday night. Heavy high elevation
mountain snow (above 6,000ft in the northern CA ranges and above
5,000ft in both the Cascade and Blue Mountains) will be underway,
but as the upper low inches closer to the Northwest U.S., falling
heights and colder temperatures aloft will cause snow levels to
lower into Monday. By 12Z Monday, NAEFS shows just about all
mandatory height levels listed are bottoming out below the 2.5
climatological percentile while IVT values >500 kg/m/s are aimed at
southern California. Then by early Tuesday the parent upper low is
expected to dive southeast across southwest OR and northern CA,
proving a final surge of Pacific moisture within an area of cold
air aloft. From northern California to the interior Northwest, the
region will also be located beneath the divergent left-exit region
of a 200mb jet streak whose wind speeds (>130 kts) are above the
99th climatological percentile. With the IVT located farther south,
the best moisture advection and upslope enhancement will be seen
from California's Siskiyou and Salmon mountains on south and west
along the spine of the Sierra Nevada. On Monday afternoon and into
Monday night, the flood of Pacific moisture aloft will advance
well inland through much of the Intermountain West. Just about
every notable mountain range in the central and northern Rockies is
likely to see measurable snow Monday night into Tuesday.
Meanwhile, cyclonic flow around the upper low will still support
ongoing upslope snowfall in the central and northern California
ranges through Tuesday night.

A very wintry few days are coming to the mountain ranges of the
western U.S.. Through 12Z Wednesday, WPC probabilities show the
northern ranges of California (Siskiyou, Salmon, Shasta) and the
length of the central and northern Sierra Nevada have high chances

70%) for snowfall totals >24". Most of these ranges above

6,000ft are currently forecast to see localized amounts between 3-4
feet through 12Z Wednesday. Heavy snow also reaches into the OR
Cascades with high probabilities for at least 12". Farther inland,
many Intermountain West ranges (Sawtooth, Blue, Uinta, Bear River,
Wind River, Absaroka, Big Horn, and CO/WY central Rockies) are all
likely to see snowfall totals of 6-12" with locally higher amounts
in these ranges as well. Expect hazardous travel conditions for
many road ways that remain open in these mountain ranges.

...Northern Plains and Upper Midwest... Day 3...

By Tuesday morning, the upper trough responsible for the barrage of
mountain snow in the West will position the 250mb jet streak's
divergent left-exit region over the Great Plains. Modest 500mb PVA
and strengthening WAA at low levels will give rise to lee
cyclogenesis east of the Rockies. Throughout the day Tuesday, a
strengthening LLJ, (NAEFS shows 850mb winds above the 90th
climatological percentile 18Z Tuesday from north Texas to the Red
River of the North), will deliver both increased moisture and
increasing WAA aloft. There also appears to be sufficiently cold
enough air present that precipitation will transition over from
rain to snow from the Black Hills on east across South Dakota and
as far east as central Minnesota Tuesday night.

There are ongoing differences in the position of this developing
deformation axis. All three deterministic guidance members
(EC/GFS/Canadian) along with the EC- AIFS all show this storm
growing in strength and size heading into Day 4, but they do this
in different ways both synoptically and on the mesoscale as well.
The ECMWF EFI does show a growing signal for a potentially
disruptive winter storm from the Dakotas on east across Minnesota
and into the northern Great Lakes, which is in line with where WSO
values of 30-80% exist on Days 3-4. Both snow amounts, along with
snow load and blowing snow are likely to be hazards that the
Northern Plains and Upper Midwest contend with through Wednesday,
with freezing rain most likely on the eastern edge of the WAA
across WI and MI. Current WPC snowfall probabilities (through 12Z
Wednesday) for >4" are 40-80% across the eastern Dakotas and
central MN, with a majority of the snow expected into Day 4.
Residents and those traveling to/from these regions should keep
close eyes on the forecast as additional changes in the types of
impacts, the severity of those impacts, and where/when these
impacts occur are likely to fluctuate for the rest of the weekend.

Snell/Mullinax
$$
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FOUS11 KWBC 030740
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
340 AM EDT Thu Apr 3 2025

Valid 12Z Thu Apr 03 2025 - 12Z Sun Apr 06 2025


...Northeast...
Days 1 & 3...

An icy wintry mix will continue from the White Mountains and
through much of interior Maine this morning as ongoing WAA and
intense 850mb FGEN sustains an icy setup over northern New England.
The lingering sub-freezing boundary layer will gradually erode as
the warm front advances northward with only northern Maine holding
on to any notable wintry mix through midday. WPC probabilities
depict low chances (10-30%) for additional ice accumulations >0.1"
in the White Mountains and western Maine through this morning.

Following a break in the action Thursday night through Saturday
morning, the next round of wintry mix arrives Saturday afternoon
as moisture from the Mississippi Valley streams northward into New
England. Similar to the Day 1 setup, low-mid level WAA and 850mb
FGEN are the primary mechanisms of lift that will promote
precipitation. The antecedent air-mass is not nearly as cold as the
Wed-Thurs air-mass. However, the modestly cold air-mass will be
tough to erode in the higher terrain, thus making the White
Mountains and western Maine the most likely areas to see a mix of
snow and freezing rain through Saturday night. WPC probabilities
show moderate- to- high chances (50-70%) for >0.1" of ice, with low
chances (10-30%) for ice accumulations >0.25".


...Intermountain West & Southern High Plains...
Days 1-3...

The weather pattern over the western third of the Lower 48 is
primarily driven by a pair of upper level disturbances; one
tracking across Montana today and early Friday, and the other is a
closed upper low over the Southwest. Starting in Montana, a cold
front at the leading edge of the 500mb shortwave trough will act as
a trigger for snow showers, some of which could have snow squall-
like impacts with bursts of snow and gusty winds Thursday
afternoon. With high pressure building in from Alberta, easterly
upslope flow into the Lewis Range and Absaroka through Thursday
evening. Snow associated with this upper trough is also expected as
far south as the Big Horns and even as far east as western North
Dakota Thursday night. By Friday morning, the cold front makes its
way south through the Central Plains and Central Rockies with
NErly upslope flow aiding in minor snow accumulations along the
Front Range of the WY/CO Rockies through Friday morning.

Farther south, the closed upper low will make its way toward New
Mexico with 200-500-700mb heights along the AZ/NM and Mexico
borders below the 10th climatological percentile. As the 700mb low
reaches western New Mexico Friday afternoon, winds over southeast
CO and northeast NM will turn easterly at the same time the
aforementioned cold front to the north plunges south. Southern CO
and northern NM will also be co-located beneath the divergent left-
exit region of a 500mb jet streak located over northern Mexico. The
heaviest snowfall looks to ensue Friday afternoon and into Friday
night across the Front Range, Palmer Divide, San Juans, and Sangre
De Cristo (including Raton Pass). By Saturday morning, snow is
forecast for most of the Southern Rockies and even parts of the
southern High Plains as the cold front continues to dive south and
the deformation zone on the northern and western periphery of the
700mb low moves in overhead. Note that with the time of year, it
will have to snow exceptionally hard (>1"/hr) for snow to
accumulate outside of the mountain ranges given the higher sun
angle and warmer soil temperatures. Still, periods of moderate snow
combined with 30-40 kt 850mb winds will cause poor visibilities
through Saturday afternoon before the snow finally tapers off
Saturday evenings.

WPC probabilities depict moderate-to-high chances (50-70%) for
snowfall >8" along the >9,000ft peaks of the Sangre De Cristo and
San Juans between Friday afternoon and Saturday afternoon. Along
the I-25 corridor, the most concerning area for heavy snowfall is
along Raton Pass where up to 12" of snow in the forecast. WSSI
depicts Moderate impact potential in the Sangre De Cristo, Raton
Mesa, and San Juans. Note that there are some Moderate Impacts in
the plains of eastern NM and the TX Panhandle with Blowing Snow the
primary impact in these areas.


Mullinax


$$
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FOUS11 KWBC 031909
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
309 PM EDT Thu Apr 3 2025

Valid 00Z Fri Apr 04 2025 - 00Z Mon Apr 07 2025

...Portions of the Rockies and the High Plains...
Days 1,2...

A deep upper level trough over much of the Intermountain West and
associated embedded upper level low over the Southwest will
gradually shift east onto the Plains through Saturday. Shortwave
disturbances moving around both the upper low and a secondary wave
moving along the Canadian border will provide the forcing for
wintry weather over and immediately downwind of those upper level
features.

For Day 1/Tonight through Friday, a potent trough over the Canadian
Prairies will dig southeastward into Montana and the Dakotas. This
will lead to pressure and height falls in the region. Troughing
developing as a response will draw a small portion of the Gulf
moisture plume into the northern Plains, supporting a widespread
generally light snowfall over Montana and the Dakotas. For the
mountains from the Bitterroots of Montana south to the Front Range
of Colorado, localized upslope along the terrain will cause much
heavier snowfall rates and amounts, especially in the Beartooths of
Montana and Bighorns of Wyoming, where new snowfall could approach
a foot through midday Friday. WPC probabilities are over 50% for 4
inches or more of snow for the Front Range of Colorado and the
Beartooths of Montana and Wyoming.

For Day 2/Friday Night and Saturday, the shortwave moving along the
Canadian border will shift east into the Great Lakes, leaving the
area. However, the upper level low/southern extension of the
broader upper trough will begin to tap ever-increasing amounts of
Gulf moisture as the lift ahead of the low moves in closer
proximity to the trough. This will draw more of that moisture
westward into the southern High Plains as the low-level jet
increases in both strength and amounts of Gulf moisture it will be
drawing northward into the nation's mid-section. Upslope will play
an even greater role here, especially as the leeside surface trough
develops over eastern New Mexico. Some of the troughing from the
northern system from Day 1 in the northern Plains will propagate
straight southward along the Front Range and support the heavy
snow. The Sangre de Cristo Mountains of Colorado and New Mexico
will be the range hardest hit with heavy snow, with WPC
probabilities for over 8 inches of snow in the moderate-to-high
(50-70%) range through Saturday evening. The WPC Winter Storm
Severity Index (WSSI) shows areas along the state line near Raton
Mesa with major impacts from the large snowfall expected. The snow
will taper off in the area Saturday night.

...Northern New England...
Day 3...

A strong upper level trough over Hudson Bay Saturday will direct a
strong shortwave along its southeastern periphery towards New
England. Meanwhile, a portion of the moisture associated with the
excessive rainfall over the nation's mid-section will draw
northeastward into the Northeast and New England. Here, that Gulf
moisture will interact with some lingering cold air over the
region, resulting in a variety of precipitation types over the
area. For areas south and west over northern New Hampshire and far
western Maine, a significant icing event is expected as warmer air
above freezing moves in aloft above the cold air in place,
resulting in precipitation changing over from snow to sleet and
freezing rain as the warm air moves in and deepens Saturday night.
There is a moderate-to-high (50-70%) chance of at least a tenth
(0.10") of an inch of ice across much of northern New Hampshire and
far western Maine near the New Hampshire border through Saturday
night, with a low (10-30%) chance of at least a quarter of an inch
of ice.

Further north where the warmer/above freezing air is unable to
reach, a light snowfall is expected, namely for far northern Maine,
where there is a low-to-moderate (30-50%) chance of at least an
inch of snow Saturday night. The moisture plume will shift east
with the cold front Sunday morning, ending the winter precipitation
threat.

Wegman

$$
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