• MESO: Heavy Rain MWUS

    From Weather Alert@454:1/105 to All on Mon Jun 13 16:54:00 2022
    AWUS01 KWNH 131824
    FFGMPD
    WVZ000-OHZ000-KYZ000-INZ000-140000-

    Mesoscale Precipitation Discussion 0350
    NWS Weather Prediction Center College Park MD
    222 PM EDT Mon Jun 13 2022

    Areas affected...West-Central to Southeast IND...Southwest
    Ohio...Northern Kentucky.

    Concerning...Heavy rainfall...Flash flooding possible

    Valid 131820Z - 140000Z

    SUMMARY...Strong thunderstorms capable of very intense short-term
    rainfall rates moving toward wetter soil conditions as complex
    matures toward late evening. Isolated flash flooding becoming
    increasingly possible.

    DISCUSSION...Please refer to SPC MCD 1143 for convective
    initiation setup indicating extremely unstable environment. As
    for excessive rainfall, the southwest low level flow is 20-25kt at
    85H and generally orthogonal to the strong temperature/instability
    axis from Northern IL to Northern Kentucky which is unsurprisingly
    aligned with highest moisture axis per CIRA LPW with sfc-85H
    supporting .7-.8" and increasing mid to upper level moisture
    upstream increasing from .2 to .4, which totals to about 2" across
    northern IL into W-central IND. Given the broad moisture flux
    convergence thunderstorms should have solid rainfall generation
    efficiency supporting over 2"/hr rates.

    Currently broad areas of individual cells are developing and are
    generally slow moving providing short-term potential for 2"
    totals, across areas of average soil saturation. Given the
    development of convection to the inflow, short-term back-building
    and training is possible especially across Ext E IL and W-Central
    IND before the cells organize a bit further. Modest divergence
    aloft and further expansion of convective cells should allow for
    increasing organization toward a convective complex in the next
    few hours across Central IND. While this will allow for increased
    forward propagation reducing rainfall duration, it will
    substantially increase moisture flux convergence along the leading
    edge and support 2"/hr totals but likely to 1-2" in less than 30
    minutes. This is concurrent with expected southeastward movement
    into areas recently affected by 200-300% of normal rainfall over
    the last week or two in SE IND/SW Ohio. Local FFG values less
    than 1.5"/hr particularly along the I-75 corridor from Dayton to
    Ohio are particularly susceptible to intense rain-rates and
    excessive runoff even outside urban settings where 0-40cm are
    running 80-95% per NASA SPoRT. Given unstable environment prior
    to the developing squall line, a few smaller precursory cells are
    possible which would further increase the potential for isolated
    localized flash flooding as the line merges. HREF probability of
    3"/3hrs reaches 10-20% between 21-00z over SE IND toward the
    Cincinnati Metro/western & southern suburbs providing some
    increased confidence in possible flash flooding even with expected
    forward speeds of the complex.


    Gallina

    ATTN...WFO...ILN...IND...JKL...LMK...RLX...

    ATTN...RFC...OHRFC...NWC...

    LAT...LON 40428731 40428655 40198464 39388226 38348233
    37698331 38378539 39238696 40008749

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