Subj : MESO: Nws Weather Prediction Center College Park Md
To   : wx-storm@lists.illinois.edu
From : COD Weather Processor
Date : Sat Aug 31 2024 22:34:48

AWUS01 KWNH 312234
FFGMPD
PAZ000-MDZ000-WVZ000-OHZ000-KYZ000-010500-

Mesoscale Precipitation Discussion 0958
NWS Weather Prediction Center College Park MD
633 PM EDT Sat Aug 31 2024

Areas affected...much northern/central WV...southeastern
OH...southwestern PA

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

Valid 312300Z - 010500Z

Summary...Isolated to widely scattered flash flooding possible
with redevelopment of convection into the early overnight hours.

Discussion...A decaying line of thunderstorms is gradually pushing
east out of the Appalachians, situated near the Blue Ridge
Mountains at the time of writing, having produced localized totals
of up to 2-4" (and scattered instances of flash flooding) over the
past 6 hours. In the wake of this line of storms, convection has
already been redeveloping ahead of a slowly approaching cold
front, as instability remains sufficient (SB/ML CAPE 500-1000
J/kg) for convection (despite the marked increase in CIN and drop
in CAPE). But the most impressive meteorological parameter remains
total precipitable water, ranging from 1.7" to a staggering 2.0"
(which is near record levels for both RNK and PIT, which are at a
lower elevation than much of the highlighted region). This
tremendous moisture, along with 20-30 kts of effective bulk shear
and wet bulb freezing heights between 14-15k feet, will allow for
continued highly efficient rainfall rates (locally 1-2"/hr).

While 12z and 18z hi-res CAMs are all over the place with their
depiction of QPF, more recent HRRR runs have come into better
agreement in suggesting additional localized totals of 2-4" along
and ahead of the cold front (through 05z). And while the HREF is
not providing a consolidated signal for QPF, it is indicating the
potential for these localized totals (per 40-km neighborhood
probabilities from the 18z HREF suggesting 10-30% odds for 3"
exceedance through 06z). Given the hydrologic sensitivity of the
region (with 3-hr FFGs generally ranging from 1.5-2.5"), isolated
to widely scattered instances of flash flooding are considered
likely.

Churchill

....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!=
DZ3fjg!41-8xvHOCCQp0U6oNnYMZXnEVWUHBtOxsKflV2_SrpTFhpUnQBJbL8hpKgwH6HEni7gw=
_935Tmu57kU17CgLV9DqU3g$  for graphic product...

ATTN...WFO...CTP...ILN...PBZ...RLX...

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

LAT...LON   41047919 41007868 40627869 40127889 39777922=20
            39437948 38947997 38448090 38318172 38588272=20
            38938326 39248318 39568238 39858173 40258097=20
            40578020=20

=3D =3D =3D
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