• DAY1SVR: Day 1 Convective Outlook Corr 1

    From COD Weather Processor@1:2320/107 to wx-storm@lists.illinois.edu on Fri Apr 3 08:10:24 2026
    ACUS01 KWNS 030810
    SWODY1
    SPC AC 030808

    Day 1 Convective Outlook CORR 1
    NWS Storm Prediction Center Norman OK
    0308 AM CDT Fri Apr 03 2026

    Valid 031200Z - 041200Z

    ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS NORTHERN
    MISSOURI AND SOUTHERN IOWA...

    CORRECTED FOR CORRECTED CATEGORICAL GRAPHIC

    ...SUMMARY...
    Storms are expected to evolve into an extensive line by Friday
    evening from Iowa to Oklahoma and northwest Texas, with the primary
    threats of large hail and damaging winds. A few tornadoes and
    isolated very large hail will be possible from northern Missouri
    into southern Iowa with any sustained supercells.

    A midlevel trough, emanating from a previous TPV, will move across
    the northern US today and tonight. This feature will maintain a
    modest surface cyclone that will progress northeastward from central
    Kansas to southern Wisconsin by Saturday morning. As the surface low
    lifts northeast, a west-east orientate warm front will push
    northward toward Lower Michigan.

    ... Northern Missouri and Southern Iowa ...

    As the surface cyclone lifts northeast in response to increasing
    pressure falls in advance of the midlevel trough, southerly winds
    will draw low-level moisture northward, with low-to-mid 60Fs
    dewpoints possible along and south of the aforementioned warm front.
    Residual steep mid-level lapse rates and modest insolation will
    contribute to MLCAPE values up to 2000 J/kg (and MUCAPE values
    approach 3000 J/kg). Despite the low-level jet weakening through the
    day, deep-layer shear will be sufficient for supercells along and
    south of the warm front and east of the Pacific cold front/dryline.
    However, given persistent warm-air advection/isentropic ascent
    associated with the advancing warm front, concerns abound regarding
    the number of storms, storm interactions, and an overall messy storm
    mode evolution.

    If a more discrete mode emerges, the overall kinematic wind field
    would support sustained supercells and an increased tornado threat
    along both the Pacific Front/dryline and the northward moving warm
    front. Very large hail would also be possible. If a more linear mode
    emerges, the primary severe hazard would focus more on strong winds
    and a QLCS tornado threat. Of note, even with a more linear mode,
    uncertainty in the coverage of potential strong convective winds is
    low owing to a weakening low-level jet and storm interactions. The
    Level 3/Enhanced was kept at this time, but the need for a
    wind-driven Level 3/Enhanced will be revisited in subsequent
    forecasts.

    ... Central Illinois east into Ohio and north into Lower Michigan
    ...

    Thunderstorms will be possible along the northward moving warm front
    during the afternoon on Friday. Although there is uncertainty
    regarding the number/coverage of storms, the overall thermodynamic
    and kinematic fields would support the potential for hail and wind
    along and north of the warm front. Across the western portions of
    this area, a brief tornado threat would exist as any discrete
    supercells traverse through the warm frontal zone.

    ... Southeast Kansas/Southwest Missouri southwest toward Northwest
    Texas...

    Thunderstorms will develop southward from northern Missouri into
    Oklahoma during the afternoon as the Pacific cold front/dryline
    pushes east into an increasingly unstable airmass. At the same time,
    additional thunderstorms are likely to develop across Northwest
    Texas and southwest Oklahoma in association with a subtle
    perturbation within the subtropical jet. Forecast wind fields
    indicate low-level flow will be weaker here than areas farther north
    and east, and have pronounced weakness in the 3-6 km AGL range. The
    combination of this wind field and the widespread nature of the
    convection would lend itself to large hail and damaging winds as the
    main severe hazards, although a tornado cannot be ruled out with any
    discrete storm or along the leading edge of any organized linear
    segments.

    ... Southwest Texas ...

    Isolated thunderstorms will be possible during the afternoon/evening
    along the higher terrain and a surface dryline. Wind fields will
    support supercells capable of producing large hail and damaging
    winds. However uncertainty regarding overall storm coverage
    precludes a categorical upgrade to Level 2/Slight Risk.

    ..Marsh/Chalmers.. 04/03/2026

    $$

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  • From COD Weather Processor@1:2320/107 to wx-storm@lists.illinois.edu on Sat Mar 21 19:38:51 2026
    ACUS01 KWNS 211938
    SWODY1
    SPC AC 211937

    Day 1 Convective Outlook CORR 1
    NWS Storm Prediction Center Norman OK
    0237 PM CDT Sat Mar 21 2026

    Valid 212000Z - 221200Z

    ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM THE
    SOUTHERN APPALACHIANS TO THE CAROLINAS...

    CORRECTED FOR GEOGRAPHIC AREA HEADLINE

    ...SUMMARY...
    Isolated strong to severe thunderstorms may produce marginally
    severe hail and damaging winds this afternoon and evening from the
    southern Appalachians into the Carolinas.

    ...20Z Update...
    The previous forecast (see below), remains on track. Please see
    Mesoscale Discussion 283 for short-term information on the severe
    threat across portions of the southern Appalachians.

    ..Squitieri.. 03/21/2026

    .PREV DISCUSSION... /ISSUED 1129 AM CDT Sat Mar 21 2026/

    ...Southern Appalachians into the Carolinas...
    Recent satellite imagery shows a somewhat subtle and broad shortwave
    trough progressing southeastward through the MS Valley, along the
    far northeast periphery of the upper ridging covering much of the
    Southwest and southern Plains. Limited low-level moisture precedes
    this wave, with recent surface analysis sampling dewpoints ranging
    from the upper 50s across much of AL to the mid 40s across much of
    the Carolinas. Modest low-level moisture advection is anticipated
    today ahead of this wave. However, this advection will be countered
    by diurnal mixing, and the general expectation is for dewpoints to
    be in the upper 40s/low 50s from eastern TN into the Carolinas as
    the wave moves in the area this afternoon. Even with this limited
    low-level moisture, cool mid-level temperatures and associated steep
    mid-level lapse rates will support weak buoyancy and the potential
    for isolated to widely scattered thunderstorms this afternoon and
    early evening.

    Large-scale ascent will be modest, supporting an initially more
    cellular, loosely organized storm mode. This region will be on the
    southern periphery of the stronger mid-level flow, likely resulting
    in sufficient shear for organization within any deeper, more
    persistent updrafts. As such, updrafts are expected to gradually
    intensify as they move into the western and central Carolinas.
    Marginally severe hail is possible with the strongest cores. A trend
    towards a more linear/line segment mode is expected with time, and
    persistent steep low-level lapse rates may support occasional strong
    to damaging downdraft winds as well. The onset of nocturnal
    boundary-layer stabilization should result in a decreasing severe
    threat as the storms move into the coastal Carolinas.

    $$

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  • From COD Weather Processor@1:2320/107 to wx-storm@lists.illinois.edu on Wed Apr 8 01:11:34 2026
    ACUS01 KWNS 080111
    SWODY1
    SPC AC 080109

    Day 1 Convective Outlook CORR 1
    NWS Storm Prediction Center Norman OK
    0809 PM CDT Tue Apr 07 2026

    Valid 080100Z - 081200Z

    ...NO SEVERE THUNDERSTORM AREAS FORECAST...

    CORRECTED FOR WORDING

    ...SUMMARY...
    Isolated thunderstorms remain possible tonight over the northern and
    southern High Plains. Severe thunderstorms are not expected.

    ...Synopsis...
    A mid-level trough continues to progress across the northern
    Rockies, providing enough mechanical lift amid cooler temperatures
    aloft to support isolated high-based thunderstorms atop a dry
    boundary layer. A low-amplitude mid-level impulse will also continue
    to traverse the southern Rockies, supporting scattered lightning
    flashes given the presence of scant buoyancy. These storms should
    gradually diminish through the evening as boundary-layer
    stabilization from nocturnal cooling takes place.

    ..Squitieri.. 04/08/2026

    $$

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  • From COD Weather Processor@1:2320/107 to wx-storm@lists.illinois.edu on Sat Apr 11 01:23:55 2026
    ACUS01 KWNS 110123
    SWODY1
    SPC AC 110121

    Day 1 Convective Outlook CORR 1
    NWS Storm Prediction Center Norman OK
    0821 PM CDT Fri Apr 10 2026

    Valid 110100Z - 111200Z

    ...NO SEVERE THUNDERSTORM AREAS FORECAST...

    CORRECTED FOR THUNDER LINE ORIENTATION

    ...SUMMARY...
    Isolated to scattered thunderstorms remain possible during the late
    evening hours across parts of the southern Plains and Great Basin;
    however, the overall severe risk appears limited.

    ...Southern Plains...
    Latest MRMS imagery depicts steady weakening of convection across
    northeast NM and across northern OK with the onset of nocturnal
    cooling and expanding convective outflows. While a couple of
    stronger storms are noted across far eastern NM and southwest TX,
    weak deep-layer wind shear and diminishing buoyancy should favor a
    weakening trend heading into the late evening hours.

    Additional elevated thunderstorms are anticipated well north of the
    stalled surface boundary along the OK/KS border with recent CAM
    guidance suggesting multi-cell clusters developing across portions
    of central to northeast KS after 03 UTC. The recent 00z DDC RAOB
    likely sampled the environment this convection will develop in, and
    hints that at least a small hail threat may materialize with
    initially discrete cells prior to upscale growth within the first
    couple of hours after initiation.

    ...Great Basin...
    Similar to the southern Plains, convective trends have largely shown
    signs of weakening over the past hour across central to northern NV
    where surface temperatures are quickly cooling into the 60s. The
    combination of rain-cooled air/outflows and the onset of nocturnal
    cooling should further reduce any remaining mixed-layer buoyancy
    (which was already fairly marginal per regional 00z RAOBs).
    Consequently, the thermodynamic environment no longer appears
    supportive of intense convection, though a strong storm or two may
    persist for the next hour as the boundary layer continues to
    stabilize.

    ..Moore.. 04/11/2026

    $$

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