• DAY1SVR: Day 1 Convective

    From Mike Powell@618:250/1 to All on Tue Apr 8 16:16:00 2025
    ACUS01 KWNS 081948
    SWODY1
    SPC AC 081946

    Day 1 Convective Outlook
    NWS Storm Prediction Center Norman OK
    0246 PM CDT Tue Apr 08 2025

    Valid 082000Z - 091200Z

    ...NO SEVERE THUNDERSTORM AREAS FORECAST...

    ...SUMMARY...
    While organized severe storms are unlikely, isolated strong storms
    may occur over far southern Florida and the Keys through early
    evening, and perhaps also across southeast Montana to the Black
    Hills.

    ...20z Update...
    No changes in forecast reasoning since the prior Outlook. The cold
    front will continue to spread south-southeastward across southern
    Florida, with thunderstorms increasingly relegated to the far
    southeast part of the Peninsula, Keys, and Florida Straits.

    ..Guyer.. 04/08/2025

    .PREV DISCUSSION... /ISSUED 1122 AM CDT Tue Apr 08 2025/

    ...South Florida/Keys...
    A cold front will continue to progress southeastward and move
    offshore by evening with scattered showers and thunderstorms
    continuing this afternoon ahead of it. While a couple of stronger
    storms could occur this afternoon through early evening, poor
    mid-level lapse rates and weak deep-layer shear should mitigate
    overall storm strength. A positively tilted shortwave trough will
    approach the region later tonight. But with the front having
    progressed offshore, thunderstorm potential (including any severe
    risk) over land should remain very low.

    ...North-central High Plains..
    A shortwave trough is forecast to move from the northern Rockies
    into the southern Canadian Prairies, while moderate mid-level flow
    expands eastward from the Pacific Northwest into the northern High
    Plains. Widely scattered high-based convection is possible during
    the afternoon and evening from southeast Montana/northern Wyoming to
    the Black Hills as modest large-scale ascent influences areas that
    have destabilized amid boundary-layer heating. Weak buoyancy should
    temper overall updraft strength, but a few instances of
    stronger/gusty thunderstorm winds may occur.

    $$
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  • From Mike Powell@618:250/1 to All on Wed Apr 9 09:17:00 2025
    ACUS01 KWNS 091235
    SWODY1
    SPC AC 091234

    Day 1 Convective Outlook
    NWS Storm Prediction Center Norman OK
    0734 AM CDT Wed Apr 09 2025

    Valid 091300Z - 101200Z

    ...NO SEVERE THUNDERSTORM AREAS FORECAST...

    ...SUMMARY...
    Thunderstorms are possible from the northern Plains into the Upper
    Midwest as well as across portions of the Midwest and central
    Plains. Severe storms are not expected.

    ...Synopsis and Discussion...
    Shortwave trough currently moving through the northern Plains is
    forecast to continue southeastward throughout the day, reaching the
    Mid MS Valley by early tomorrow. Some modest amplification of this
    shortwave is expected as a jet streak progresses through it base. An
    attendant surface low, currently over southeast NE, will move
    eastward just ahead of its parent shortwave, reaching the Mid MS
    Valley tonight and the middle OH Valley by early tomorrow morning.
    An associated cold front will push southeastward through MO, KS and OK.

    Limited moisture return will keep buoyancy muted ahead of the front,
    keeping the potential for surface-based thunderstorm development
    along the front low. Cooling mid-level temperatures and moistening low/mid-levels will likely result in isolated elevated thunderstorms
    across IL during the early evening. Persistent warm-air advection
    along the front should allow for isolated thunderstorms to continue
    throughout the evening and overnight across central/southern IN, KY,
    and western/middle TN. An isolated instance or two of small hail is
    possible but any severe threat should be tempered by limited
    buoyancy.

    Farther west, a separate, lower amplitude shortwave trough is
    expected to move eastward from the northern Rockies into the
    northern/central Plains. Large-scale ascent attendant to this
    shortwave will spread into the northern and central Plains near peak
    heating. Modest airmass destabilization is anticipated from the
    Black Hills across NE where deep mixing is likely, as well as
    farther north from eastern MT/western ND into MN where cold
    mid-level temperatures are expected. Isolated thunderstorms are
    possible within these corridors. Overall severe potential will be
    very low, but the high-based character of these storms could result
    in a strong downdraft or two.

    ..Mosier/Kerr.. 04/09/2025

    $$
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  • From Mike Powell@618:250/1 to All on Sun Apr 13 08:38:00 2025
    ACUS01 KWNS 131241
    SWODY1
    SPC AC 131239

    Day 1 Convective Outlook
    NWS Storm Prediction Center Norman OK
    0739 AM CDT Sun Apr 13 2025

    Valid 131300Z - 141200Z

    ...NO SEVERE THUNDERSTORM AREAS FORECAST...

    ...SUMMARY...
    Thunderstorm development will be possible from the Upper Mississippi
    Valley into the Great Lakes, and from the central Rockies to the
    lower Missouri Valley. Severe storms are not expected.

    ...Synopsis...
    A midlevel shortwave trough will move eastward from the northern
    High Plains to the Upper MS Valley by early Monday, as a remnant lee
    cyclone develops northeastward from eastern NE to Lake Superior.
    Limited low-level moisture return is underway within the warm sector
    of the cyclone, though sufficient ascent/saturation is not occurring
    until near the IA/MN border where elevated thunderstorms may develop
    later this morning. This elevated convection will then spread
    eastward over WI through the day and Lower MI by late evening.

    Otherwise, isolated thunderstorms will be possible this afternoon
    into early tonight along a southward-moving cold front across CO,
    and overnight into MO where moistening and weak ascent atop the
    frontal surface (near 700 mb) could support elevated convection
    09-12z.

    ..Thompson/Dean.. 04/13/2025

    $$
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  • From Mike Powell@618:250/1 to All on Mon Apr 21 07:01:00 2025
    ACUS01 KWNS 210530
    SWODY1
    SPC AC 210528

    Day 1 Convective Outlook
    NWS Storm Prediction Center Norman OK
    1228 AM CDT Mon Apr 21 2025

    Valid 211200Z - 221200Z

    ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
    THE UPPER OHIO VALLEY AND CENTRAL GULF STATES...

    ...SUMMARY...
    A few strong storms are possible across the upper Ohio Valley and
    across portions of the central Gulf States. Gusty winds and
    marginally severe hail are the primary risks.

    ...Upper Ohio Valley...

    Mid-MS Valley short-wave trough is forecast to eject into the upper
    Great Lakes region by mid day as 70+kt 500mb speed max translates
    across northern IN into southern ON. 500mb wind fields will
    strengthen across the upper OH Valley in response to this feature as
    heights are suppressed ahead of the short wave. Latest model
    guidance suggests the associated cold front will surge into western
    OH/KY by 18z, subsequently advancing into western PA later in the
    evening. Modest boundary-layer heating should contribute to adequate
    buoyancy for robust updrafts, and scattered convection should
    develop ahead of the front as temperatures warm through the 70s.
    Gusty winds may accompany this activity, along with some risk for
    marginally severe hail.

    ...Central Gulf States...

    Synoptic front will trail across the TN Valley through the central
    Gulf States today serving as the focus for thunderstorms as
    convective temperatures are breached along this weakly-forced
    boundary. While 0-6km bulk shear should only be modest across this
    region, seasonally high PW values and MLCAPE in excess of 1500 J/kg
    suggest some risk for gusty winds and hail. Boundary-layer heating
    should prove instrumental in convective updraft strength today.

    ..Darrow/Squitieri.. 04/21/2025

    $$
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  • From Mike Powell@618:250/1 to All on Tue Apr 22 08:08:00 2025
    ACUS01 KWNS 221248
    SWODY1
    SPC AC 221246

    Day 1 Convective Outlook
    NWS Storm Prediction Center Norman OK
    0746 AM CDT Tue Apr 22 2025

    Valid 221300Z - 231200Z

    ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
    THE SOUTHERN/CENTRAL PLAINS...

    ...SUMMARY...
    Isolated to scattered severe thunderstorms will be possible across
    parts of the southern/central Plains, mainly this afternoon and
    evening. Large hail and severe gusts should be the main threats.

    ...Southern/Central Plains...
    Stronger westerly flow aloft should remain confined to the northern
    tier of the CONUS today, and to the north of the surface warm
    sector. Multiple weak mid-level disturbances may drift eastward
    across the southern/central High Plains through this evening, with
    fairly modest mid-level flow for late April standards. At the
    surface, a front will extend from parts of the Upper Midwest to
    southwest KS near a weak surface low. A dryline will extend
    southward from this low over the southern High Plains. Some eastward
    mixing of the dryline is forecast by late afternoon, especially
    across the OK/TX Panhandles. Otherwise, little movement of the front
    is anticipated through this evening.

    Both of these surface boundaries should provide some focus for
    convective development this afternoon and evening, even with
    large-scale forcing for ascent remaining rather nebulous. Weak to
    locally moderate instability should develop through the afternoon
    with diurnal heating of a partially modified Gulf airmass. Even
    though west-southwesterly mid-level flow is expected to remain
    fairly modest, weak low-level winds gradually veering/strengthening
    with height though mid/upper levels should support sufficient
    deep-layer shear for some updraft organization. A mix of widely
    spaced supercells and multicells may eventually develop along both
    the front and dryline, with uncertainty remaining rather high about
    favored locations for robust convective development. Regardless,
    this activity could pose a threat for isolated to scattered large
    hail given steep lapse rates aloft. Any clusters that can evolve
    through the late afternoon and evening may also have some severe
    wind threat given steep low-level lapse rates. Some trimming was
    made to the northwest extent of severe probabilities based on the
    forecast position of the front/dryline later today.

    ...Southeast to the Carolinas...
    A weak front draped southwest to northeast is forecast to move
    little today across the Southeast. Generally modest
    west-southwesterly mid-level flow is expected to prevail, with
    slightly stronger winds aloft forecast over the Carolinas. This
    should tend to limit deep-layer shear and convective
    organization/intensity. Still, with some destabilization forecast
    and fairly cool temperatures aloft, any clusters of convection that
    can develop along/south of the front may pose an isolated threat for
    damaging winds and perhaps marginally severe hail. Based on latest observational and guidance trends showing greater thunderstorm
    coverage this afternoon across parts of AL into northern GA, have
    connected the two Marginal Risk areas with this update.

    ..Gleason/Broyles.. 04/22/2025

    $$
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