• DAY1SVR: Day 1 Convective Outlook Corr 1

    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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  • From COD Weather Processor@1:2320/107 to wx-storm@lists.illinois.edu on Thu Apr 16 06:11:07 2026
    ACUS01 KWNS 160611
    SWODY1
    SPC AC 160609

    Day 1 Convective Outlook CORR 1
    NWS Storm Prediction Center Norman OK
    0109 AM CDT Thu Apr 16 2026

    Valid 161200Z - 171200Z

    ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON
    ACROSS PARTS OF WESTERN AND CENTRAL NEW YORK INTO SOUTHERN
    VERMONT...

    CORRECTED FOR TYPOS AND WORDING

    ...SUMMARY...
    A few severe thunderstorms are possible this afternoon in a corridor
    across western through central New York (state) and adjacent
    southern Vermont.

    ...Discussion...
    A significant mid-level trough and embedded low now digging across
    the Pacific Northwest is forecast to split as it continues inland
    through this period. One perturbation, perhaps including a
    continuing cyclonic circulation, is forecast to turn eastward across
    the northern Rockies through the central Canadian/U.S. border area.
    Another perturbation is forecast to dig southeastward across the
    Great Basin into early Friday. It appears that the larger-scale
    evolving troughing will be preceded by a significant cold frontal
    surge to the lee of the northern U.S. Rockies, through much of the
    northern and central Great Plains by 12Z Friday.

    Downstream, initially prominent mid-level ridging centered near the
    southern Atlantic Seaboard is forecast to become increasingly
    suppressed, as one short wave trough, approaching southwestern
    portions of the Great Lakes region early today, turns eastward then southeastward across the lower Great Lakes vicinity into northern
    Mid Atlantic. It appears that this will be trailed by another
    perturbation, which is forecast to progress east of the Ozark
    Plateau through the lower Ohio and Tennessee Valleys, before digging
    across the southern Appalachians, downstream of short wave ridging
    building across and east of the mid/upper Mississippi Valley.

    ...Mid South into lower Great Lakes and Northeast...
    The primary and trailing short wave troughs advancing to the east of
    the Mississippi Valley are forecast to be preceded by the remnants
    of overnight convection across parts of the lower Great Lakes, Ohio
    Valley, and Mid South at the outset of the period. The impacts of
    associated cloud cover and outflow on destabilization within the
    warm sector of a broad, but weak, surface low migrating northeast of
    the lower Great Lakes during the day remain unclear. However,
    various model output, including convection allowing guidance,
    suggest that destabilization and strengthening shear along a warm
    frontal zone (as it strengthens with differential heating) may
    become a focus for organized strong thunderstorm development across
    New York state by afternoon. It appears that this may include an
    evolving cluster, perhaps preceded by more discrete thunderstorm
    activity, in an environment conducive to evolving supercell
    structures, with potential to produce severe hail, wind and a risk
    for a couple of tornadoes.

    Additional thunderstorm activity may eventually develop and
    strengthen, accompanied by at least a risk for strong to severe wind
    gusts by late afternoon, in a corridor of stronger daytime heating
    ahead of a developing cold front spreading into the upper Ohio
    Valley/Allegheny and Cumberland Plateau.

    Farther west/southwest, there is not a well-defined signal in the
    latest model output, but a corridor of differential surface heating
    along weakening trailing convective outflow across the Mid South
    vicinity could become a focus for supercell development. It
    currently appears that this potential could peak across north
    central into northeastern Arkansas by late this afternoon, aided by
    moderate boundary-layer destabilization and stronger mid-level
    forcing for ascent associated with a cyclonic vorticity center
    migrating across the region.

    ...Southern Great Plains...
    Moderate to strong potential instability is forecast to develop
    beneath steep lapse rates, along and east of a dryline which likely
    will be retreating westward across the high plains by early this
    evening. While this will be conditionally supportive of severe
    thunderstorm development, forcing to support initiation of sustained thunderstorms remains unclear, aside from, perhaps, the higher
    terrain near/east of the Texas Big Bend. Beneath moderate to strong southwesterly mid/upper flow, this could include an isolated
    supercell or two which could propagate across the Rio Grande River,
    before weakening in the presence of increasing inhibition this
    evening.

    ..Kerr/Lyons.. 04/16/2026

    $$

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  • From COD Weather Processor@1:2320/107 to wx-storm@lists.illinois.edu on Fri Apr 17 17:05:19 2026
    ACUS01 KWNS 171705
    SWODY1
    SPC AC 171703

    Day 1 Convective Outlook CORR 1
    NWS Storm Prediction Center Norman OK
    1203 PM CDT Fri Apr 17 2026

    Valid 171630Z - 181200Z

    ...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS FROM FAR
    NORTHWEST OKLAHOMA THROUGH CENTRAL AND EASTERN KANSAS INTO
    WEST-CENTRAL MISSOURI...

    CORRECTED FOR ORIENTATION OF THE 45% HAIL PROBABILITIES

    ...SUMMARY...
    Numerous severe thunderstorms are likely this afternoon into tonight
    across parts of the Upper Midwest southward across the lower
    Missouri Valley and central/southern Great Plains. Initially this
    may be accompanied by a risk for large to giant hail and a few
    strong tornadoes, before severe wind gusts of 60 to 90 mph become
    the most prominent hazard by this evening.

    ...Synopsis...
    Recent surface analysis places a low over south-central MN, with a
    cold front extending southwestward to another low over central KS. A
    warm front also extends southwestward from the MN low through far
    southwest MN and far northern IL into central IN. This warm front is
    demarcated well by the 56 deg F isodrosotherm. Farther south, a
    dryline extends from the triple point KS low back southwestward
    through the TX Panhandle and into far southeast NM. A broad, moist
    warm sector exists to the east of the cold front and dryline,
    characterized largely by dewpoints in the low to mid 60s.

    A well-defined shortwave trough is apparent on satellite imagery,
    extending from southern Saskatchewan back southwestward into the
    eastern Great Basin. This wave is forecast to continue eastward,
    with a attendant increase in the mid-level flow across much of the
    Plains and Upper/Mid MS Valley. The cold front will surge eastward/southeastward in response to this wave as well, interacting
    with the warm sector to support numerous strong to severe
    thunderstorms from parts of the Upper Midwest southward across the
    lower Missouri Valley into southern Plains.

    ...Upper/Mid MS Valley...
    Moderate to strong low-level moisture advection is expected across
    the Upper MS Valley today as the surface low mentioned in the
    synopsis progresses northeastward, with an attendant northward shift
    of the warm front as well. The risk across this region may evolve in
    several phases, beginning with the elevated thunderstorms currently
    ongoing across northwest WI. This storms will likely continue
    northeastward, posing a risk for severe hail and isolated damaging
    gusts. Additional development is possible northwest of this activity
    along the occluded front, with some hail possible here as well.

    Farther south, the northeastward advecting low-level moisture
    coupled with strong heating and steep lapse rates will result in a
    strongly unstable airmass along and just south of the warm front by
    the early afternoon. Storm initiation is anticipated within this
    open warm sector by early afternoon, forced by a mix of warm-air
    advection, low-level confluence, and subtly increasing large-scale
    ascent. This activity should be ahead of the front and initially
    discrete. The overall parameter space will be characterized by
    strong to very strong buoyancy, moderate deep-layer vertical shear,
    and strong low-level helicity. Supercells capable of all hazards are
    expected, including large to very large (i.e. 3"+ hail), strong to
    intense tornadoes, and severe wind gusts. Storm interactions are
    expected to strongly influence the tornado risk, with the initially
    discrete mode likely becoming messy quickly.

    Farther west, other storms are likely to evolve quickly along the
    front, developing into a band of severe thunderstorms that will push
    east coincident with the front. Damaging wind gusts will tend to
    become more prevalent during the evening with linear storm modes.
    Some tornado risk may continue into the evening as maturing bands of
    storms yield a threat for bowing segments and embedded mesovortices,
    before this activity gradually diminishes late as it moves east into
    IN/Lower MI late.

    ...KS/OK/MO...
    A very unstable airmass is expected to develop along and ahead of
    the triple point over south-central KS an associated cold front and
    dryline. Strong low-level convergence will likely lead to initial
    storm development near the triple point. This initial activity will
    be supercellular and capable of very large to giant hail (over
    3-3.5" in diameter). Highest coverage of very large hail is expected
    over from far northwest OK into south-central KS. Strong downdrafts
    (60 to 80 mph) are possible as well. With a largely
    boundary-parallel orientation to the deep-layer shear, the tornado
    risk appears relatively lower. However, given the supercell mode and
    potential interactions with outflow, a low-probability tornado risk
    remains. A more north-south configuration to the dryline supports a
    conditional tornado risk into far northwest TX.

    With time, upscale growth and the development of a
    forward-propagating MCS is anticipated across central and eastern
    KS. Very strong gusts (80+ mph) are possible with this MCS.
    Additionally, some QLCS tornado risk will exist within this line as
    long as it stays ahead of the surging cold front. The front will
    continue sweeping southeastward, with storms along this boundary
    yielding a risk for wind/hail.

    ..Mosier/Chalmers.. 04/17/2026

    $$

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