Subj : MESO: Nws Weather Prediction Center College Park Md
To   : wx-storm@lists.illinois.edu
From : COD Weather Processor
Date : Mon Jun 26 2023 23:32:17

AWUS01 KWNH 262332
FFGMPD
VAZ000-270430-

Mesoscale Precipitation Discussion 0592
NWS Weather Prediction Center College Park MD
731 PM EDT Mon Jun 26 2023

Areas affected...East-Central VA

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

Valid 262330Z - 270430Z

Summary...Rainfall rates as high as 1-3"/hr expected to lead to
additional 2-4" localized totals. Isolated to widely scattered
instances of flash flooding are likely.

Discussion...A cluster of thunderstorms is gradually organizing
across east-central VA this afternoon, producing rainfall rates as
high as 1-3"/hr (per MRMS estimates). This cluster is moving into
the vicinity of the Richmond metropolitan area, with concerns for
slowing propagation (as the upwind propagation vectors favor
easterly motions of only 5-10 kts). The mesoscale environment is
currently characterized by ML CAPE of 1500-2500 J/kg, PWATs of
1.5-1.7 inches (nearing the 90th percentile, per WAL sounding
climatology), and effective bulk shear of 30-40 kts. This may
allow convection to further grow upscale into a convective
complex, but even if the cluster remains fairly disorganized there
is likely to be some localized training/repeating of 1-3"/hr
rates, given the southwest to northeast orientation of convection.

The 18z HREF has not handled this particular region very well
through the afternoon, failing to show a meaningful signal for
convective organization across east-central VA. Even so, HREF
40-km neighborhood probabilities for 2" and 3" exceedance depict a
local maxima of 10% near the Richmond area through 06z, and the
HRRR has occasionally also depicted an isolated total of an
additional 2-3". Given that FFGs across the MPD area are as low as
1.5-2.0" over a 3-6 hour period (generally across the corridor
from Richmond southeast to Norfolk), 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!93HORAvnAtoG84YIgDrVUG0RVYerh731YEr6Ibnadf8hLQBJcDoJacgXFyaO79mD4hn8=
l4UL6vcHGsb9VmwdTWjsRzA$  for graphic product...

ATTN...WFO...AKQ...LWX...RNK...

ATTN...RFC...MARFC...SERFC...NWC...

LAT...LON   38217807 38167675 37337579 36677613 36617705=20
            36827854 37247905=20

=3D =3D =3D
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