Subj : Heavy Rain/Flood KYINTNVA
To   : All
From : Dumas Walker
Date : Thu Aug 01 2024 07:59 am

AWUS01 KWNH 010905
FFGMPD
VAZ000-TNZ000-KYZ000-INZ000-011500-

Mesoscale Precipitation Discussion 0774
NWS Weather Prediction Center College Park MD
504 AM EDT Thu Aug 01 2024

Areas affected...portions of central and eastern KY...surrounding
portions of IN/TN/VA

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

Valid 010900Z - 011500Z

Summary...Expected localized rainfall rates of 1-2"/hr may lead to
localized totals of 2-4". Isolated to scattered instances of flash
flooding are possible.

Discussion...Moisture and instability are steadily increasing
early this morning across much of central/eastern KY and
surroundings, mainly due to low-level flow (925-850 mb) increasing
with the noctural enhancement of the low-level jet (LLJ). Most
evidently, 3-hr changes of 100 mb mean mixing ratio +1-2 g/kg and
ML CAPE of +200-600+ J/kg have occured (per 08z SPC mesoanalysis),
and precipitaible water values range from 1.5-1.9 inches (between
the 75th and 90th percentile, per BNA/ILN sounding climatology).
With effective bulk shear of 30-40 kts, any convective initiaton
that is able to occur is capable of organization/longevity (as a
recent persistent isolated storm near Livingstone/Jamestown, TN
made quite clear, producing 2-3"/hr rainfall rates for a time).

While the robustness and coverage of convection are somewhat in
question, there is enough of a hi-res model signal to indicate
that isolated to scattered instances of flash flooding will be
possible this morning (with 2" and 3" exceedance probabilities
from the 00z HREF 40-km neighborhood method indicating 20-30% and
~10% odds, respectively, corresponding with average 6-hr Flash
Flood Guidance thresholds). While individual HREF members are
inconsistent with their depictions of convection, more recent HRRR
runs have suggested that localized 2-3" are possible (with rates
mostly peaking between 1-2"/hr with ESE storm motions indicated to
be near 15 kts with little to no training expected).

Churchill

ATTN...WFO...ILN...JKL...LMK...MRX...OHX...PAH...

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

LAT...LON   38738407 37518262 36278277 36068403 36658567 
            37198699 38618640 
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