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  • DAY1SVR: Day 1 Convective Outlook Corr 1

    From COD Weather Processor @1:2320/107 to All on Tue Aug 18 14:12:22 2026
    ACUS01 KWNS 181412
    SWODY1
    SPC AC 181410

    Day 1 Convective Outlook CORR 1
    NWS Storm Prediction Center Norman OK
    0910 AM CDT Tue Aug 18 2026

    Valid 181300Z - 191200Z

    ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM NORTHEAST
    KANSAS INTO CENTRAL MISSOURI...

    CORRECTED FOR WIND CIG1 LINE ORIENTATION

    ...SUMMARY...
    Thunderstorms with severe wind gusts and isolated large hail will be
    possible this afternoon and evening from the central Plains into the
    lower Missouri Valley. Isolated severe gusts and hail will also be
    possible from the Northern Rockies into the central High Plains, and
    eastward into the Midwest and southern Lower Michigan. Damaging
    gusts could also occur across parts of Mississippi and Alabama.

    ...Central Plains into Lower MO Valley...
    Warm-air advection showers and thunderstorms are currently ongoing
    across south-central/southeast NE. This activity is likely
    reinforcing an outflow boundary from an earlier MCS that extends
    from northwest KS into the NE/KS/MO border vicinity. These showers
    and thunderstorms are expected to continue southeastward over the
    next few hours, while gradually diminishing in coverage and
    intensity. How this outflow modifies will influence the thunderstorm
    potential across northern KS this afternoon. If the boundary does
    not wash out, there could be a region of notable convergence that
    develops across in the northwestern/north-central KS between the
    outflow (reinforced by an approaching cold front) and a heat-driven
    surface low that develops across western KS. Even with this
    potential convergence, convective initiation is uncertain. Most
    guidance maintains warm low/mid level temperatures, with the
    resultant capping suppressing any thunderstorm development. Steep
    lapse rates, moderate deep-layer vertical shear, and strong buoyancy
    are expected north of the boundary, and there is a conditional risk
    for large to very large hail and strong downdrafts if any updrafts
    can mature.

    A more certain scenario is expected farther east across eastern KS,
    where evening thunderstorm development is anticipated as the
    low-level jet increases. Steep lapse rates and moderate vertical
    shear support the potential for thunderstorms capable of large hail
    during the initially more cellular mode. These storms will likely
    cluster quickly, with a trend towards upscale growth into a
    forward-propagating MCS which then moves into MO. Damaging gusts
    will become the primary risk once this occurs.

    ...Northern Rockies through the Central High Plains...
    A shortwave trough is forecast to progress southeastward from
    British Columbia/Alberta into the northern Rockies. Thunderstorm
    development is anticipated across the northern Rockies as this wave
    interacts with the destabilized and buoyant airmass across the
    region. Moderate westerly flow will accompany this wave as well,
    supporting the potential for more organized storm structures and the development of several line segments. These widely scattered
    thunderstorms are forecast to progress eastward/southeastward this afternoon/evening, with additional development possible from WY into
    the central High Plains. The moderate westerly flow aloft, high
    storm bases, and steep low-level lapse rates support the potential
    for strong to severe wind gusts as these storms progress eastward/southeastward.

    ...Southern WI/northern IL into Lower MI...
    Low-level moisture is expected to increase across the Midwest ahead
    of an approaching cold front, resulting in moderate buoyancy by the
    late afternoon. Convergence along the front will be weak but still
    sufficient for convective initiation, with the combination of
    moderate buoyancy and moderate westerly flow aloft supporting strong
    to severe storms. An initially more cellular mode could yield large
    hail within the strongest storms. A quick transition towards more
    linear modes is anticipated, with damaging gusts becoming the
    primary severe risk within any strong line segments.

    ...MS/AL...
    Afternoon thunderstorm development is anticipated across MS and AL
    as a weak vorticity maximum progresses southeastward into the warm,
    moist, and unstable environment in place across the region. Vertical
    shear will be weak, and an outflow-dominant, multicellular mode is
    expected. Even so, some clustering into one or more line segments
    appears probable, resulting in scattered thunderstorm coverage.
    Steep low-level lapse rates and relatively high cloud bases support
    the potential for strong downdrafts with any more robust convection.

    ..Mosier/Bunting.. 08/18/2026

    $$

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    --- scorpsmtpd
    * Origin: capitolcityonline.net * KY, USA (1:2320/107)
  • From COD Weather Processor @1:2320/107 to All on Fri Aug 21 06:48:14 2026
    ACUS01 KWNS 210648
    SWODY1
    SPC AC 210646

    Day 1 Convective Outlook CORR 1
    NWS Storm Prediction Center Norman OK
    0146 AM CDT Fri Aug 21 2026

    Valid 211200Z - 221200Z

    ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PORTIONS OF
    THE CENTRAL PLAINS...THE MIDWEST AND THE CAROLINAS...

    CORRECTED FOR TEXT

    ...SUMMARY...
    Scattered damaging hail (some greater than 2 inch diameter) and
    severe wind gusts may occur over parts of the central Plains this
    afternoon and evening. Scattered storms, some with severe wind gusts
    and hail, also are possible across parts of the Midwest. Scattered
    to numerous storms with damaging wind gusts are possible over the
    Carolinas and Southeast.

    ...Central Plains...
    Mid-level ridging over the western US is forecast to intensify,
    strengthening northwesterly flow aloft over much of the central US.
    Several embedded disturbances will pass overhead with the enhanced northwesterlies through the day. A surface low will move
    southeastward through the Great Lakes as a weak trailing cold front
    moves southward through the central Plains and Midwest.

    Ahead of the front, a plume of steep mid-level lapse rates will
    shift eastward across the central Plains toward the Mid-MO Valley
    atop a corridor of rich low-level moisture. Diurnal destabilization
    should result in 3000-4000 J/kg of MLCAPE from SD to NE. Isolated to
    widely scattered thunderstorm development is expected from the Black
    Hills southeastward along the cold front. Elongated/straight
    hodographs and 45+ kt effective shear will favor initial supercells.
    Large to very large hail (some greater than 2 inches diameter) will
    be possible. With time, a forward propagating cluster or two may
    develop and move southeast across parts of NE and KS with the
    potential for severe gusts (a few near 70-80 mph). It is unclear
    exactly how far southeast any storms will persist overnight, but any
    more substantial clustering could allow at least an isolated severe
    threat to continue into early Saturday.

    A much drier and hotter environment over the High Plains to the west
    could also support isolated to widely scattered high-based storms
    from eastern CO into western KS. Very steep lapse rates in the
    lowest 2-3 km with modest buoyancy aloft could allow a few severe
    gusts.

    ...Midwest...
    Beneath the upper trough over the western Great Lakes, cool
    mid-level temperatures and robust surface moisture should result in
    moderate destabilization from WI into eastern IA and northwest IL.
    Scattered thunderstorms by mid afternoon ahead of the cold front
    spreading southeastward. Enhanced northwesterly flow with deep-layer
    shear of 30-40 kt will promote a mix of organized clusters and
    supercells. The large buoyancy will support a risk for damaging
    gusts and some hail.

    ...Southeast and Gulf Coast...
    A broad upper trough will move across the central US into parts of
    the southern Appalachians while a weak cold front moves southward
    from the mid Atlantic today and tonight. Weak ascent from the upper
    trough and near the front should focus diurnal thunderstorm activity
    across the Carolinas and southern Appalachians. Warm surface
    temperatures and plentiful boundary-layer moisture will support
    large buoyancy (3000+ J/kg MLCAPE) through the afternoon and evening
    despite modest mid-level lapse rates. With scattered to numerous
    storms expected, a few organized clusters may emerge with a risk
    primarily for damaging wind gusts. Slight enhancement of the
    westerly flow aloft could also support some isolated hail with the
    stronger updrafts.

    Farther south and west, a very humid and warm air mass is forecast
    to become strongly unstable by early afternoon across the lower MS
    Valley and Gulf Coast. Scattered to numerous thunderstorms are
    expected along prior outflows and a weak, southward moving cold
    front from East TX into LA/MS. The very strong buoyancy and high
    PWAT content will support clustering and strong downdrafts with
    sporadic damaging gust potential. Otherwise, weak vertical shear
    will limit overall organization.

    ..Lyons/Weinman.. 08/21/2026

    $$

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    --- scorpsmtpd
    * Origin: capitolcityonline.net * KY, USA (1:2320/107)