• DAY1SVR: Day 1 Convective Outlook Corr 1

    From COD Weather Processor@1:2320/105 to wx-storm@lists.illinois.edu on Tue Feb 17 20:14:26 2026
    ACUS01 KWNS 172014
    SWODY1
    SPC AC 172013

    Day 1 Convective Outlook CORR 1
    NWS Storm Prediction Center Norman OK
    0213 PM CST Tue Feb 17 2026

    Valid 172000Z - 181200Z

    ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS COASTAL
    CALIFORNIA AND PORTIONS OF NEBRASKA AND IOWA...

    CORRECTED FOR NDFD COLOR FILL ISSUE

    ...SUMMARY...
    Isolated strong thunderstorms will be possible across parts of the
    West today through tonight. Isolated thunderstorms are also
    anticipated across the Upper Midwest late this afternoon and
    tonight.

    ...Eastern Nebraska and southwestern Iowa...
    Near the base of a negative-tilt shortwave trough and a pronounced
    100+ kt mid-level jet, strong ascent is expected to develop late
    this afternoon amid a mixed and modestly moist air mass. Cool
    mid-level temperatures and surface dewpoints in the 40s and 50s F
    may allow a few hundred J/kg of buoyancy to develop. This
    destabilization and strong ascent may support a fast-moving arc of
    high-based showers/thunderstorms, particularly where surface
    temperatures reach into the 60s and dewpoints hold above 40 F.

    While buoyancy will be weak, dry low-levels and strong
    dynamics/background flow could support efficient downward mixing of
    momentum to the surface. Isolated severe/damaging gusts are possible
    this afternoon and evening from parts of eastern NE into
    west-central IA. Convection should weaken rapidly with eastward
    extent

    Elsewhere, isolated strong storms remain possible across portions of
    the CA coast ahead of a strong secondary upper trough. This is most
    likely overnight with a few damaging gusts or a brief tornado the
    primary risks owing to very strong flow and modest inland moisture
    advection. No changes were made to the outlook here, see the prior
    discussion for more info.

    ..Lyons.. 02/17/2026

    .PREV DISCUSSION... /ISSUED 1031 AM CST Tue Feb 17 2026/

    ...Synopsis...
    Recent satellite imagery shows several disturbances across the
    western CONUS, including a pair of low-amplitude shortwave troughs
    within the belt of strong southwesterly flow extending from the
    central Pacific into the central Plains and a deepening upper low
    off the Pacific Northwest coast. Intense surface cyclogenesis is
    anticipated ahead of the lead shortwave as it moves quickly
    northeastward, with the resulting surface low forecast to move
    across SD/NE, ending the period over southern MN. Evolution of this
    surface low and parent shortwave, which will become increasingly
    negatively tilted throughout the day and overnight, will result in
    strong forcing for ascent from the Mid MO Valley into the Upper
    Midwest this evening and overnight.

    Farther west, the previously mentioned upper low is expected to drop
    slowly southward as a strong jet (i.e. 100 kt at 500 mb) pivots
    around its western and southern periphery. Very cold mid-level
    temperatures and strong/persistent forcing for ascent will support
    isolated thunderstorms along across much of the West coast
    throughout the day and tonight.

    ...Coastal California...
    Limited buoyancy is expected to develop along the near coastal areas
    of CA as very cold mid-level temperatures (i.e. -25 to -30 deg C at
    500 mb) associated with the upper low continue to advect into the
    region. This buoyancy coupled with the strong forcing for ascent
    could result in some deeper, more persistent updrafts across the
    region today, both within the primary frontal band and any more
    bowing line segments that may follow it. Given the robust deep layer
    flow across the region, any deeper, more persistent updrafts could
    result in some stronger, convectively augmented gusts. Additionally,
    there appears to be enough low-level curvature to support a brief
    tornado or two within the immediate coastal regions. Highest
    potential for either hazards currently appears to be after 00Z in
    the San Luis Obispo/Santa Barbara county areas.

    ...Upper Midwest...
    Some low-level moisture return is anticipated across the region
    ahead of the previously mentioned shortwave trough and associated
    forcing for ascent. Even so, low-level moisture will still be
    limited, with dewpoints likely remaining in the upper 40s to perhaps
    low 50s. This is not expected to be enough moisture for surface
    destabilization across most of the region, despite strong surface heating/boundary-layer mixing and steepening low-level lapse rates
    in vicinity of the surface low/front. The only exception is across
    far southeast SD and far northeast NE where a high-based storm or
    two cannot be completely ruled out. Any that does develop could
    produce an strong gust or two, although coverage will likely remain
    less than 10%.

    Across the Upper Midwest, capping may tend to largely prevail during
    the day, with elevated thunderstorms becoming more probable
    east-northeastward of IA into the MN/WI throughout the evening and
    overnight. Instability does not appear strong enough to support
    severe hail with this elevated activity.

    $$

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  • From COD Weather Processor@1:2320/105 to wx-storm@lists.illinois.edu on Fri Feb 20 05:46:46 2026
    ACUS01 KWNS 200546
    SWODY1
    SPC AC 200545

    Day 1 Convective Outlook CORR 1
    NWS Storm Prediction Center Norman OK
    1145 PM CST Thu Feb 19 2026

    Valid 201200Z - 211200Z

    ...NO SEVERE THUNDERSTORM AREAS FORECAST...

    CORRECTED FOR GENERAL THUNDERSTORM LINES

    ...SUMMARY...
    Widely-scattered thunderstorms may occur today over parts of the
    Southeast and Mid Atlantic. Severe storms are not forecast.

    ...Synopsis/Discussion...
    A shortwave trough will move quickly across the Great Lakes and into
    the Northeast, with a surface low developing off the coastal Mid
    Atlantic. Over land, a cold front will push east across VA and the
    Carolinas, with rapid drying from the west. Despite this, a few showers/thunderstorms will be possible prior to the front moving
    offshore. Warm profiles aloft suggest weak storms, but strong
    westerlies just off the surface could support gusty winds.

    To the south, the tail end of this front will stall in east-west
    fashion across LA and southern MS/AL/GA. This boundary will move
    northward overnight across parts of MS/AL/GA, with increasing
    southwest flow at 850 mb ahead of another wave moving across the
    southern Plains. Meanwhile, height tendencies aloft will be neutral.
    While showers and a few thunderstorms may occur in this warm
    advection regime late in the day and overnight, it appears warm
    profiles aloft should reduce hail potential despite strong
    deep-layer shear.

    ..Jewell/Halbert.. 02/20/2026

    $$

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  • From COD Weather Processor@1:2320/105 to wx-storm@lists.illinois.edu on Sat Feb 21 20:23:32 2026
    ACUS01 KWNS 212023
    SWODY1
    SPC AC 212021

    Day 1 Convective Outlook CORR 1
    NWS Storm Prediction Center Norman OK
    0221 PM CST Sat Feb 21 2026

    Valid 212000Z - 221200Z

    ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON
    AND EVENING ACROSS PARTS OF THE SOUTHEAST STATES...

    CORRECTED FOR GENERAL THUNDERSTORM LINE ERROR

    ...SUMMARY...
    Isolated strong/severe thunderstorms remain possible across parts of
    the Southeast this afternoon and evening.

    ...Southeast States...
    Other than trimming risk areas behind the sagging cold front, no
    important changes have been made to the ongoing forecast.

    ..Hart.. 02/21/2026

    .PREV DISCUSSION... /ISSUED 1011 AM CST Sat Feb 21 2026/

    ...Southeast States...
    A well-defined surface baroclinic zone extends from southern LA/MS east-northeastward into parts of AL/GA/SC today. To the south of
    the boundary, a rather warm/moist and unstable air mass is present
    with dewpoints in the upper 60s and afternoon MLCAPE values of
    1000-1500 J/kg. This will lead to occasional thunderstorms along
    the boundary through the day and into the evening. Low-level winds
    are veered, limiting convergence and vertical shear. However,
    occasional small bowing structures will be possible today capable of
    gusty or locally damaging wind gusts. Also, modest mid-level lapse
    rates and cool temperatures aloft might result in a report or two of
    hail. Refer to MCD #110 for further short-term details.

    $$

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  • From COD Weather Processor@1:2320/105 to wx-storm@lists.illinois.edu on Tue Mar 3 20:34:08 2026
    ACUS01 KWNS 032034
    SWODY1
    SPC AC 032032

    Day 1 Convective Outlook CORR 1
    NWS Storm Prediction Center Norman OK
    0232 PM CST Tue Mar 03 2026

    Valid 032000Z - 041200Z

    ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS THE
    SOUTHERN/CENTRAL PLAINS INTO MISSOURI AND WESTERN ILLINOIS...

    CORRECTED FOR TESTING THE CORRECTION PROCESS

    ...SUMMARY...
    Isolated severe hail may occur this evening into the overnight hours
    across parts of the southern/central Plains into Missouri and
    western Illinois.

    ...20z Update...
    The Marginal Risk continues across parts of the southern/central
    Plains into Missouri and western Illinois. Moisture continues
    northward, observed in visible satellite and 60 F dew points
    increasing from the south into southern Kansas. Thunderstorm
    development is still expected to be delayed into the evening as
    modest capping remains in place. Some conditional risk for large
    hail (some up to 1.5-2" in diameter) will be possible, mainly across
    northwest Oklahoma into southern Kansas. In this region, a favorable
    overlap of MLCAPE around 1000-1500 J/kg will overlap with steep
    mid-level lapse rates and deep layer shear near the frontal
    boundary.

    ..Thornton.. 03/03/2026

    .PREV DISCUSSION... /ISSUED 1030 AM CST Tue Mar 03 2026/

    ...Southern/Central Plains into Missouri and Western Illinois...
    Water-vapor imagery this morning shows a mid-level shortwave trough
    over the central Rockies and this feature will move into the central
    High Plains late tonight. A frontal zone this morning is draped
    from near the Raton Mesa into the TX Panhandle extends
    east-northeastward across northern OK into the Ozarks. A weak
    surface low over northeast NM and the OK/TX Panhandles this morning
    will gradually develop towards northwest TX by this evening.
    Southerly low-level flow will maintain a moist fetch into OK today
    and into the Ozarks and parts of the mid MS Valley. A dryline is
    forecast to mix eastward across the southern High Plains by late
    this afternoon, intersecting the surface front in the northwest
    TX/southwest OK vicinity.

    Convection will likely be inhibited during the day across much of
    the MRGL Risk owing to both capping and weak mid-level shortwave
    ridging. The strongest heating and low-level convergence is
    forecast across parts of northwest TX/southwest OK where convective
    inhibition will become weakened by late afternoon. Have adjusted
    severe hail probabilities farther south into parts of northwest TX
    to account for the potential for a supercell or two this evening
    into the overnight hours. As large-scale forcing for ascent
    continues to strengthen through the evening into the overnight,
    expected widely scattered thunderstorms to eventually develop near
    the frontal zone (perhaps favoring a northwest OK/southern KS
    corridor). Large hail will be the hazard with the stronger storms.
    Around 1000-1500 J/kg of MUCAPE, steepened mid-level lapse rates,
    and strong effective bulk shear suggest that some of these cells may
    pose a threat for isolated severe hail as they spread from OK/KS
    into MO and western IL through early Wednesday morning.

    $$

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