• DAY1SVR: Day 1 Convective Outlook Amend 1

    From COD Weather Processor@1:2320/105 to wx-storm@lists.illinois.edu on Mon Jul 22 22:04:43 2024
    ACUS01 KWNS 222204
    SWODY1
    SPC AC 222202

    Day 1 Convective Outlook AMEND 1
    NWS Storm Prediction Center Norman OK
    0502 PM CDT Mon Jul 22 2024

    Valid 222155Z - 231200Z

    ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS
    OF NORTH DAKOTA AND NORTHWEST MINNESOTA...THE DESERT SOUTHWEST...AND
    THE MID-ATLANTIC/EASTERN NORTH CAROLINA...

    AMENDED FOR ADDITION OF HAIL/WIND PROBABILITIES IN NORTH DAKOTA AND
    NORTHWEST MINNESOTA

    ...SUMMARY...
    Isolated severe thunderstorms remain possible this afternoon and
    early evening over portions of North Dakota and northwest Minnesota,
    the mid-Atlantic region, as well as western Arizona to the lower
    Colorado River Valley.

    ...North Dakota/Northwest Minnesota...
    Isolated strong to severe thunderstorms are ongoing along a weak boundary/low-level confluence axis across parts of northeast ND and
    northwest MN. A few instances of large hail have already occurred.
    The presence of moderate to locally strong instability, along with
    marginally favorable deep-layer shear with modestly strengthening
    northwesterly winds at mid/upper levels, should support a continued
    threat for isolated severe hail and strong to damaging winds as this
    activity spreads slowly southward across ND and northwest MN late
    this afternoon and early evening. 5% severe hail/wind probabilities
    have been included with this amendment to account for this
    potential. See Mesoscale Discussion 1695 for additional details on
    the short-term severe threat across this region.

    ...Previous Discussions...

    ...20Z Discussion...
    Aside from minor line adjustments to affect recent/local trends, no
    appreciable changes appear to be needed, with respect to the ongoing
    forecast. Prior reasoning continues to reflect expectations
    regarding convective/severe risk through the end of the period.

    ...1630Z Discussion...
    ...Mid-Atlantic states...
    A narrow ribbon of slightly enhanced southwesterly 500-mb flow will
    remain across NC/Delmarva to the southeast of a broad/weak mid-level
    trough centered over the Great Lakes southwestward through the
    Ozarks. Although large-scale forcing will be modest, a seasonably
    moist airmass (14-16 g/kg lowest 100-mb mean mixing ratios per 12
    UTC area raobs) will gradually destabilize through the mid
    afternoon. Midday visible satellite imagery shows the initial
    stages of a building cumulus field across the Carolinas northward
    into eastern VA. Widely scattered to scattered thunderstorms are
    forecast to develop this afternoon within the moderately unstable
    airmass. Some strengthening in south-southwesterly 850-mb flow is
    progged by models later this afternoon into the early evening. A
    few of the stronger storms may pose a localized risk for damaging
    gusts (45-60 mph). If a transient supercell can develop (primarily
    21-01z), a brief tornado is possible. This activity will likely
    diminish by mid-late evening owing to nocturnal stabilization.

    ...Western AZ/lower CO River Valley...
    Widely scattered thunderstorms are forecast to develop later this afternoon/evening as surface temperatures soar into the 100s.
    Although flow will be weak due to proximity to the mid- to
    upper-level ridge, large surface temperature-dewpoint depressions
    (around 50 deg F) will favor evaporative cooled downdrafts with the
    more robust thunderstorm cores. A few severe gusts (60-70 mph) are
    possible before this activity wanes by mid evening.

    ...Southeast New England...
    Model guidance indicates increased shower/thunderstorm potential
    late tonight (08-12 UTC) as a strengthening LLJ shifts northeastward
    from the Mid-Atlantic coast to near the continental shelf/deep
    Atlantic waters off the southeast New England coast. The latest
    models generally indicate meager to no surface-based buoyancy
    penetrating the coast, thus precluding low-severe probabilities this
    outlook update.

    ..Gleason.. 07/22/2024


    $$

    = = =
    To unsubscribe from WX-STORM and you already have a login, go to https://lists.illinois.edu and use the "Unsubscribe" link. Otherwise email Chris Novy at cnovy@cox.net and ask to be removed from WX-STORM.

    --- SBBSecho 3.20-Linux
    * Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105)
  • From COD Weather Processor@1:2320/105 to wx-storm@lists.illinois.edu on Thu May 1 22:05:07 2025
    ACUS01 KWNS 012204
    SWODY1
    SPC AC 012203

    Day 1 Convective Outlook AMEND 1
    NWS Storm Prediction Center Norman OK
    0503 PM CDT Thu May 01 2025

    Valid 012000Z - 021200Z

    ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF
    THE OHIO VALLEY AND ACROSS TEXAS AND OKLAHOMA....

    AMENDED FOR INCREASED TORNADO PROBABILITIES ACROSS CENTRAL TX.

    ...SUMMARY...
    Lines and/or clusters of strong to severe thunderstorms are likely
    to impact parts of the Ohio Valley into lower Great Lakes, parts of
    the lower Mississippi Valley, and the southern Great Plains through
    tonight.

    Localized tornado risk has recently materialized across parts of
    central TX in proximity to a differential heating zone and a weakly
    confluent dryline. Several supercells ongoing within extreme
    buoyancy (4000+ J/kg of MLCAPE) may pose a risk for an additional
    tornado in proximity to the boundary given slightly enhanced
    low-level shear, very moist conditions and very strong vertical
    stretching.

    ...20z...
    The broad and rather nebulous severe threat continues across much of
    the central and eastern CONUS. Damaging wind and marginally severe
    hail potential will continue across parts of the OH Valley ahead of
    the intensifying band of thunderstorms this afternoon/evening.
    Trimming was done behind the line over the lower Great lakes and
    Midwest, where limited forcing for ascent, less buoyancy and weaker
    vertical shear are in place. While an isolated stronger storm
    remains possible, the lack of greater storm organization should
    curtail higher severe potential through the remainder of today.

    Farther south across the Mid MS and TN Valley, isolated strong to
    occasionally severe storms will remain possible over a broad area
    this afternoon. The warm and moist air mass will support some risk
    for occasional strong, water-loaded downdrafts with damaging gust
    potential. However, the coverage of severe storms appears low and
    the SLGT has been removed.

    Otherwise, the severe risk remains largely unchanged over parts of
    the Southern Plains. Isolated storms, including a few supercells,
    are possible over parts of central TX with a risk for damaging winds
    and very large hail. High-based convection ongoing over southeastern
    CO should continue to gradually grow upscale into this evening over
    parts of the TX/OK Panhandles. Damaging gusts and some hail are
    possible. By late tonight, an increasingly strong southerly
    low-level jet will support the development of additional storms
    ahead of this complex. Merging cells and bowing structures will pose
    a risk of damaging gusts, hail and isolated tornadoes overnight
    across parts of central OK and the Red River valley.

    ..Lyons.. 05/01/2025

    .PREV DISCUSSION... /ISSUED 1109 AM CDT Thu May 01 2025/

    ...OH Valley...
    Morning water vapor imagery shows a progressive and large shortwave
    trough moving across parts of MO/IL. Forcing ahead of this trough
    will lead to scattered thunderstorm development over eastern IN and
    central KY, with storms spreading northeastward through the
    afternoon and early evening. Forecast soundings show deep and
    moderately strong southwest flow aloft. This coupled with
    sufficient CAPE will pose a threat of organized lines/clusters of
    storms capable of damaging wind gusts. Activity is expected to
    spread into western NY/PA during the early evening before weakening.


    ...Central TX...
    A weak surface boundary extends from west-central LA westward into
    central TX this morning. Strong heating and ample moisture
    along/south of the boundary will yield max CAPE values over 4000
    J/kg by late afternoon. Most 12z CAM solutions indicate at least
    isolated intense convection forming in this corridor. Those storms
    that form will pose a risk of very large hail and damaging winds.
    Other intense storms may form off the high terrain of northern
    Mexico and build into parts of central TX this evening.

    ...TX Panhandle into OK...
    A combination of strong heating and upslope low-level winds into the
    Raton mesa will aid in the development of a cluster of thunderstorms
    over southeast CO this afternoon. This activity will track
    southeastward into a progressively more moist/unstable air mass over
    the TX panhandle and western OK, where a few more intense storms are
    expected. Cells and bowing structures will pose a risk of large
    hail and damaging winds. By late tonight, other storms are expected
    to form ahead of this complex, affecting parts of central OK with a
    risk of large hail.

    $$

    = = =
    To unsubscribe from WX-STORM and you already have a login, go to https://lists.illinois.edu and use the "Unsubscribe" link. Otherwise email Chris Novy at cnovy@cox.net and ask to be removed from WX-STORM.

    --- SBBSecho 3.20-Linux
    * Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105)