FOUS11 KWBC 161949
QPFHSD
Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
249 PM EST Mon Feb 16 2026
Valid 00Z Tue Feb 17 2026 - 00Z Fri Feb 20 2026
...Pacific & Interior Northwest...
Days 1-3...
An active period of winter weather expected this week across the
Pacific and Interior Northwest as repeated shortwaves dive through a
longwave trough entrenched across the region.
The period begins with increasing southerly mid-level flow
downstream of the lead shortwave which will be digging along the
British Columbia coast. This shortwave will continue to expand
southward, with the trough axis finally moving onshore WA/OR Tuesday
night. This impulse will continue to track eastward into the Great
Basin and Northern Rockies on Wednesday, with a secondary shortwave
moving onshore immediately in its wake. This mid-level evolution
will push 500mb heights down below the 0.5 climatological percentile
tonight through Wednesday morning, leading to snow levels for which
the NBM suggests will fall below 1000 ft as far as northern CA, with
the 10th percentile (which may be a better proxy due to steep lapse
rates beneath the cold core trough aloft) dropping to the surface
across most of the area. While the heaviest precipitation is
expected within surges of WAA D1 and D3, this could result in the
first light snowfall accumulations down to the valley floors and
lowlands of WA and OR.
For D1, the heaviest precipitation is expected across OR and into
ID, as well as the southern WA Cascades. Here, the IVT will maximize
within the broad WAA plume and within broad mid-level
divergence/height falls downstream of the lead shortwave trough.
Additionally, S/SW flow will impinge favorably into the Cascades for
upslope enhancement, with snow levels falling well below pass
levels, including potentially even to I-5 through the Willamette
Valley. The heaviest snow is expected above 2,000 ft, where WPC
probabilities are high (>70%) D1 and low (30%) D2 for 4+ inches each
day, leading to locally more than 12 inches of snowfall through
00Z/Thursday. This will create hazardous travel, especially across
Santiam, Willamette, and Siskiyou Passes. Light snow accumulations
are expected even onto the Coastal terrain of WA/OR where there
exists a 30-50% chance of at least 2 inches.
A brief break in precipitation is expected much of D2 before the
second shortwave approaches with renewed ascent and moisture
spreading into the area. A period of renewed snow is likely,
especially across the WA/OR Cascades and surrounding lowlands as
snow levels again fall below 500 ft. WPC probabilities for at least
1 inch of snow reach 30% even into the Portland, OR metro area and
surrounding Seattle, WA, with an additional 6+ inches of snowfall
likely (70% chance) across the southern WA and most of the OR
Cascades.
...California...
Days 1-3...
...Multiple days of heavy and disruptive snowfall to affect the
California mountain ranges this week...
A series of potent Pacific storm systems are working together to
direct copious amounts of moisture at the mountain ranges of the
"Golden State". While heavy snow has been unfolding in the
Siskiyou, Shasta, Trinity, and Salmon mountains of northern CA
since Sunday, very heavy snowfall has been ongoing today along the
Sierra Nevada with snow levels currently between 5,000 and
6,000ft. Tonight, the snow levels will drop precipitously to then
falling to as low as 2,500ft by Tuesday morning in the northern
Sierra, and 4,000 ft for the southern Sierra Nevada. Snowfall rates
between 1-2"/hr will be common with some instances of >3"/hr
snowfall rates in the central and southern Sierra Nevada. Heavy
snow will continue through tonight in the Transverse Ranges above
6,000ft. This first disturbance is the result of a strong shortwave
trough that will be pivoting east into California through this
evening. By Tuesday morning that upper level energy will be well
into the Intermountain west, through upsloping and a surface trough
will keep higher elevation snow going through tonight, albeit with
decreasing intensity.
On Tuesday, another round of heavy snow is expected across just
about all of the CA mountain ranges as a second, arguably stronger
upper level low dives south along the West Coast, closely following
the first. This will spike onshore flow and additional moisture
supply on the southern and eastern flanks of the upper low. Renewed
heavy snow will start out across the northern California ranges
Tuesday morning, then spread south down the Sierra Nevada from
Tuesday afternoon through Tuesday night. Once again, 1-2 inch/hour
rates will be common with 3-4 inch/hour rates locally not out of
the question. Snow levels will continue to fall to around 1,000 ft
in far northern California (including the northern coastal range)
Tuesday night, around 2,500ft in the Sierra Nevada, and between
4,000 and 5,000 ft into the Transverse Ranges. Snow will continue
to fall across California's mountain ranges trough Wednesday as yet
another 500mb shortwave trough west of WA continues to sustain
what feels like an endless supply of Pacific moisture into the
Golden State. However, during the day Wednesday snowfall rates
could diminish in most of the mountains down to light snow or even
flurries at times. With the longwave trough overhead, snow levels
could creep down as low as 1,000ft in central CA and may support
minor accumulations down to 1,000ft.
On Thursday a pair of shortwaves, both moving SSE, but one
impacting the Northern California ranges, and the other following
the previous disturbances hugging the coast until it turns inland
over Southern California, will keep moderate snow ongoing along
most of California's ranges. Rates will not be quite as heavy on
Thursday as on previous days. Snow levels will fall in the
Transverse Ranges to as low as 3,500 feet Thursday morning, while
staying between 1,500 and 2,500 feet from the Sierra Nevada north.
California's mountain ranges welcome the snow, although it will
come down fast and furious through mid-week. Through the end of
this discussion's timeframe (00Z Fri), snowfall will be measured
in feet above 4,000ft along the Sierra Nevada. WPC probabilities
show high chances (>90%) for >30" of snow along Donner Pass through
00Z Friday and more snow still to come. The WSSI shows a large
swath of Extreme Impacts (Substantial disruptions to daily life;
extremely dangerous travel or impossible driving conditions,
extensive closures) for elevations generally above 5,000ft,
although some Major impacts as low as 4,000ft are possible. Major
to locally Extreme impacts are showing up in the peaks of the San
Gabriel and San Bernadino mountains, with mostly Moderate-to-Major
Impacts (increasingly more disruptive to travel jumping from
Moderate to Major). There are also likely to be some Major impacts
in the Coastal Range of northwest CA above 2,000ft. Note that there
are Minor to locally Moderate Impacts expected along I-5 around
Mount Shasta, signifying potential travel delays for I-5 in the
more elevated terrain of northern CA.
...Intermountain West...
Days 1-3...
Pacific moisture ahead of the longwave upper trough off the West
Coast will spill over the Cascades and Sierra Nevada and reach many
ranges across the Intermountain West this week that badly need the
boost in snowpack. With a lack of a frigid airmass ahead of this
healthy moisture source, the bulk of the heavy snow will be largely
confined to many of the taller mountain peaks. The heaviest
snowfall on Monday will reside in the Blue, Sawtooth, Wind River,
Uinta, and as far south as Mt. Charleston and the Mogollon Rim. WPC
72-hour probabilities are high (>70%) for snowfall totals >12" in
these mountain ranges through Thursday afternoon.
On Tuesday, the highly anomalous upper-low off the Pacific NW coast
will help to usher the initial upper low over southern CA east into
the Intermountain West, causing widespread height falls and a
larger plume of Pacific moisture to pass over the Rockies. The
potent closed low then heads inland over the interior NW and
northern Rockies on Wednesday while opening up into a trough,
prompting snow levels to crash and most valleys are likely to see
at least a coating of snow. Still, the lack of a frigid airmass at
the surface will keep the bulk of the heavy snow in the mountains
with ranges such as the Wasatch, Bear River, Tetons, Uinta, Wind
River, Mogollon Rim, and CO Rockies seeing anywhere from 1-2 feet
of snow. Expect Minor to Moderate Impacts, per the WSSI, with
travel over passes from the Lewis Range and Bitterroots to as far
south as the Mogollon Rim likely to contend with hazardous travel
conditions.
By Thursday, much of the Intermountain West will be in a lull
between storm systems, as the next in the series of shortwaves
moves across California. Some snow will spill over into much of
Nevada, while areas further east see the snow stop completely
during the day. Snow with the shortwave over California moves
across the Four Corners into Thursday night and Friday.
...Northern Plains & Upper Great Lakes...
Days 2-3...
A shortwave emerging form the Great Basin will track rapidly
northeast Tuesday, reaching the Dakotas Tuesday evening while
amplifying. As this trough becomes negatively tilted and expands
across the Northern Plains/Upper Midwest, it will interact with the
LFQ of a strengthening subtropical jet streak arcing from the Desert
Southwest to the Great Lakes, to support surface cyclogenesis
Tuesday evening. This low is then expected to move very slowly
through Wednesday before gradually filling over the Western Great
Lakes Thursday night.
As this low tracks slowly eastward, it will interact with impressive
IVT surging above the 99th climatological percentile into Minnesota,
with the accompanying moisture and theta-e ridge axis then wrapping cyclonically around the system and lifting into a pronounced TROWAL.
The associated synoptic lift, aided by increasing WAA, will expand precipitation across the northern tier of the CONUS from far eastern
MT through the western Great Lakes, with periods of heavy snow
likely as strongly sloped FGEN driving omega into the TROWAL
supports heavy precipitation rates. The most impressive ascent
appears to intersect the DGZ, so despite this being subjectively
elevated (nearing 500mb) it will support heavy snow rates and
dynamic cooling into a column that is initially too warm to support
snow. However, once precipitation changes to snow, it will become
heavy, supported by the WAA/fgen beneath the TROWAL and accompanying
CSI evident in cross-sections, to support rates that will likely
exceed 1"/hr at times (60-90% chance). These intense rates will be
accompanied by strong and gusty winds, resulting in widespread
moderate impacts (30-60% chance) from ND through the Arrowhead of
MN. Here, there is a high probability (>70% chance) of more than 4
inches of snowfall accumulating, with locally 8-10 inches possible.
Some even higher totals, exceeding 12 inches, may occur (30-50%
chance) along the Arrowhead of MN where upslope flow with lake-
enhanced moisture will combine to bring greater snowfall and
resulting impacts.
Additionally, with the pronounced WAA rotating around the surface
low, an area of freezing rain is also expected, especially from near
Duluth, MN eastward across northern WI and into northern MI where
the warm nose will be most prevalent, but low-level easterly flow
will maintain sub-freezing surface temperatures. In this area, WPC probabilities are moderate (50-70%) for at least 0.1" of ice, with
locally more than 0.25" possible, most likely across the northern
L.P. of MI.
...Northeast...
Days 2-3...
A strong surface low moving slowly across the Dakotas/Minnesota
Wednesday will remain entrenched within an elongated mid-level
trough extending into the Mid-Atlantic states. Vorticity lobes
downstream of this wave will spread northeast from the Mid-Atlantic
states into the Northeast, before getting sheared rapidly to the
east as mid-level flow becomes strongly confluent south of secondary
shortwave energy crossing Maine and Nova Scotia. The resultant mid-
level PVA and divergence will overlap with a narrow ribbon of
impressive low-level WAA to produce a stripe of heavy precipitation
from Upstate NY through southern/central New England.
This precipitation will expand eastward from the Great Lakes
Wednesday morning, exiting off the New England coast by Thursday
morning. While the guidance continues to feature some latitudinal
variability within what will likely be a narrow corridor of
precipitation, the evolution of the upper jet streak (initially
downstream a poleward arcing, but becoming more zonal and stretch
south of the precipitation) will force a quasi-laterally translating
band of precipitation, but with slow weakening of intensity through
Thursday morning. This is reflected by just modest fgen in the 925-
850mb layer, and although some fgen may increase late as a surface
wave develops offshore leading to more pronounced low-level
convergence over New England, this will occur as the column dries
from the top down, limiting moist ascent, so most of the
precipitation should remain of modest intensity, with locally higher
rates possible, especially Wednesday, during the period of most
impressive WAA.
Thermally, the antecedent column is marginal to support wintry
precipitation, and it appears any significant snowfall accumulations
will be confined to higher elevations above 1,000 ft, or where the
most intense dynamic cooling can overwhelm the above-freezing low-
levels. This is most likely from Upstate NY into western VT where
conditional instability into a DGZ of modest depth is possible (30%
chance from the SREF). This will support briefly heavier snowfall
rates, which could linger as the band of precipitation tracks
along its long axis. This is reflected by WPC probabilities that
reach as high as 10-30% for 4+ inches of snow, especially in the
Adirondacks and Greens, with moderate probabilities for 2+ inches
covering much of central New England and the northern half of
Upstate NY. It is important to note that the WSE mean snowfall for
much of this area lies well below the maximum values, so some
locally higher amounts are probable where any banding persists.
South of this axis of moderate to heavy snow, a corridor of icing
exceeding 0.1" is possible (10-30% chance) from the southern shore
of Lake Ontario through the capital region of NY near Albany.
...Central Plains...
Day 3...
The same shortwave that brings heavy snow to California Tuesday
night and spreads over much of the Intermountain West during the
day on Wednesday will eject out into the Plains starting Wednesday
night. This will cause lee cyclogenesis over northern Colorado.
That low will then track east into Kansas, then turns northeast
into Iowa by Thursday evening. To the north and west of the low
track, chances for impactful snow have been increasing. While
there remains considerable uncertainty both in track and amounts
with this storm, agreement has been increasing. The swath of
heaviest snow, on the order of 4-6 inches, extends from far
southeast Montana through a portion of Wyoming and South Dakota,
and into north-central Nebraska. WPC 72-hour probabilities are
moderate (40-60%) for 4 inches of snow in this region Wednesday
night into Thursday.
Weiss/Wegman
$$
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