• Meso Discussions 248/249 Severe Threat

    From Mike Powell@618:250/1 to All on Wed Mar 19 19:22:07 2025
    ACUS11 KWNS 192225
    SWOMCD
    SPC MCD 192224=20
    KYZ000-INZ000-ILZ000-200030-

    Mesoscale Discussion 0248
    NWS Storm Prediction Center Norman OK
    0524 PM CDT Wed Mar 19 2025

    Areas affected...portions of the lower Ohio River Valley

    Concerning...Tornado Watch 58...

    Valid 192224Z - 200030Z

    The severe weather threat for Tornado Watch 58 continues.

    SUMMARY...Thunderstorms are beginning to develop across southeast
    Illinois into western Kentucky. These storms are expected to
    intensify and pose a severe threat as they move eastward across the
    lower Ohio River Valley over the next few hours.

    DISCUSSION...Very gradually deepening convection, cooling cloud-top temperatures, and occasional lightning flashes have been noted over
    the past 30-60 minutes across the lower OH River Valley. Despite the
    slow convective evolution thus far, a combination of steadily
    improving low-level moisture (in the form of mid 50s dewpoints) and
    increasing deep-layer ascent within the left-exit region of the
    mid-level jet should lead to a gradual increase in storm coverage
    over the next 1-2 hours across southern IN and western KY. Buoyancy
    within the narrow warm sector will remain fairly meager (around 500
    J/kg MLCAPE), but low to mid-level winds have been increasing over
    the past hour with the approach of the mid-level jet, which is
    bolstering low to mid-level wind shear per regional VWPs. This
    favorable kinematic profile should compensate for the limited
    buoyancy and support organized convection downstream from where
    cells are currently developing. Given nearly 300 m2/s2 0-1 km SRH
    and 50-60 knot flow sampled within the lowest 1-2 km, severe gusts
    and tornadoes should remain the primary hazard.

    ..Moore.. 03/19/2025

    ATTN...WFO...LMK...IND...PAH...

    LAT...LON 36858879 37378858 38198811 38398792 38508771 38588640
    38528602 38358581 37938585 37668601 37368625 37138646
    37058674 36698840 36728869 36788878 36858879

    ACUS11 KWNS 192334
    SWOMCD
    SPC MCD 192334=20
    ALZ000-TNZ000-KYZ000-MSZ000-200130-

    Mesoscale Discussion 0249
    NWS Storm Prediction Center Norman OK
    0634 PM CDT Wed Mar 19 2025

    Areas affected...Western and middle Tennessee into northern
    Mississippi and northwest Alabama

    Concerning...Severe potential...Watch unlikely=20

    Valid 192334Z - 200130Z

    Probability of Watch Issuance...20 percent

    SUMMARY...Thunderstorm development is expected between 7-9 PM CDT
    across western Tennessee and northern to central Mississippi with a
    downstream risk for severe hail and damaging winds. The risk is
    expected to remain sufficiently isolated to preclude watch issuance.

    DISCUSSION...GOES visible imagery shows gradually deepening cumulus
    along and just ahead of a diffuse dryline/Pacific front from western
    TN southward into MS. This trend is expected to continue as
    mid-level temperatures continue to cool with the eastward
    progression of the primary trough axis, resulting in improving
    700-500 mb lapse rates that will be more favorable for sustained
    convection. This trend is already being observed further north
    across the lower OH River Valley, suggesting that thunderstorm
    development is becoming more likely for areas further south. Modest
    surface moisture (mid 50s dewpoints) will continue to limit overall
    buoyancy values (MLCAPE should be maximized around 500-750 J/kg),
    but wind fields over the region are supporting elongated hodographs
    that will promote organization of the more intense updrafts. Weak
    off-boundary storm motions/deep-layer shear vectors suggest that a
    combination of semi-discrete cells and clusters is likely later this
    evening as storms move into middle TN and northwest AL. Given the
    convective environment and trends in latest CAM guidance, a few of
    the more intense cells/clusters may pose a severe hail/wind threat
    through the late evening.

    ..Moore/Hart.. 03/19/2025

    ATTN...WFO...OHX...BMX...HUN...PAH...MEG...JAN...

    LAT...LON 32909031 35998919 36458887 36538846 36628750 36588700
    36448652 36178623 35758610 35048619 34208674 33358759
    32638848 32468899 32458937 32478982 32549002 32679022
    32909031
    $$
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