028
AWUS01 KWNH 231907
FFGMPD
VAZ000-NCZ000-SCZ000-TNZ000-KYZ000-240036-

Mesoscale Precipitation Discussion 0308
NWS Weather Prediction Center College Park MD
307 PM EDT Thu May 23 2024

Areas affected...TN Valley...Southern Appalachians

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

Valid 231906Z - 240036Z

Summary...Thunderstorm coverage is increasing across the TN Valley
and Southern Appalachians. Rainfall rates upwards of 2-2.5"/hr
with this activity support a scattered flash flooding threat this
afternoon.

Discussion...Scattered thunderstorms continue to blossom across
the TN Valley, ahead of an approaching shortwave evident in
moisture channel imagery over Southeast Missouri. Filtered
insolation across the region and dewpoints in the mid-upper 60`s
has allowed the airmass to recover across the region in the wake
of storms earlier today, with 1500-2000 J/kg MLCAPE and 1.5-1.6"
PWATs (1-1.5 sigma above climatology) estimated over the TN Valley
from SPC Mesoanalysis. While current effective shear profiles
around the convection are somewhat weak (20-30 kts), a recent
hourly rainfall estimate exceeding 2"/hour from KMRX suggests the
most robust updrafts are realizing the very moist and unstable
environment for efficient rainfall production.

Going through the afternoon, additional thunderstorm coverage is
expected with the approach of the forcing from the west. A
modifying outflow boundary may act to focus the activity
initially, although generally coverage will remain scattered
without a focused low level boundary. CAM guidance has struggled
all day with initializing convection owing to the more subtle
nature of the forcing, although the 12Z HREF neighborhood
probabilities suggest a moderate to high (50-60%) likelihood of at
least 1 hour rainfall rates continuing through 0Z tonight with
recent runs of the HRRR suggesting 2-2.5"/hour rates possible.
This could support scattered instances of flash flooding this
afternoon, as the region remains vulnerable to heavy rainfall with
1 HR FFGs as low as 1.5-0.5"/hour noted across the region.

Asherman

...Please see www.wpc.ncep.noaa.gov for graphic product...

ATTN...WFO...GSP...JKL...LMK...MRX...OHX...PAH...RNK...

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

LAT...LON   38188519 37408389 36488142 35138192 35008418
            35568651 36438734 37728680