Subj : MESO: WVa Heavy Rain/Floo
To   : All
From : Mike Powell
Date : Mon Aug 28 2023 09:06:00

AWUS01 KWNH 281215
FFGMPD
WVZ000-281700-

Mesoscale Precipitation Discussion 0995
NWS Weather Prediction Center College Park MD
813 AM EDT Mon Aug 28 2023

Areas affected...much of West Virginia

Concerning...Heavy rainfall...Flash flooding likely

Valid 281210Z - 281700Z

Summary...Scattered flash flooding, some significant, likely to
continue through the late morning hours.

Discussion...Impressive training bands of efficient, warm rain
process dominated convection have developed early this morning
across central WV. A surface trough and associated strong theta-e
gradient are providing the focus for convection, while deep layer
(850-300 mb) southwesterly flow is allowing for training (as it is
parallel to the surface trough). The mesoscale environment is
otherwise characterized by weak (but clearly sufficient) ML CAPE
of 100-250 J/kg, PWATs of 1.2-1.6" (like near the 90th percentile,
extrapolating from PIT/RNK sounding climatology and accounting for
elevation), and effective bulk shear near 20 kts. In addition, the
height of the freezing level is estimated to be near ~13k feet.
That is quite notable, considering that warm rain processes are
quite dominate.

CAMs (including the 00z HREF and more recent HRRR runs) have been
handling the ongoing convection quite poorly, suggesting only 30%
odds of 1" exceedance through 12z. In reality, MRMS suggests
localized totals have exceeded 3" (just southeast of Charleston),
with a larger stripe of estimates 1" exceedance (with one
observation supporting a near 4" total, and many supporting the 1"
exceedance). 1-2"/hr rainfall rates will likely continue
considering the environment, and realized hourly totals may
approach 3" locally where convection efficiently trains. Therefore
scattered instances of flash flooding are likely to continue,
including locally significant (i.e. life threatening) flash
flooding (particularly near low water crossings and poor drainage
areas).

Churchill

ATTN...WFO...PBZ...RLX...RNK...

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

LAT...LON   39617972 39067953 38427986 37968032 37528106 
            37838202 38338210 38788163 39148089 39408034 
            

= = =
--- SBBSecho 3.14-Linux
 * Origin: Ilink: CCO - capitolcityonline.net (454:1/105)

.