Subj : MESO: Nws Weather Prediction Center College Park Md
To   : wx-storm@lists.illinois.edu
From : COD Weather Processor
Date : Mon Aug 28 2023 15:44:10

AWUS01 KWNH 281544
FFGMPD
VAZ000-NCZ000-282140-

Mesoscale Precipitation Discussion 0996
NWS Weather Prediction Center College Park MD
1143 AM EDT Mon Aug 28 2023

Areas affected...southeastern Virginia and northeastern North
Carolina

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

Valid 281540Z - 282140Z

Summary...Rainfall rates of 1-3"/hr are expected to lead to
localized totals of 3-6" through the afternoon. Isolated to
scattered instances of flash flooding are likely.

Discussion...Convective converge has been increasing late this
morning across portions of the southern Mid-Atlantic (in the
vicinity of a coastal front along the NC coastline). While there
is not a lot of low-level frontogentic forcing or moisture
transport, the air mass in place is anomalously moist with
increasing instability from daytime heating (despite a large
amount of cloud cover across the region). The mesoscale
environment is characterized by ML CAPE of 500-1000 J/kg (up by
about 100-300 J/kg over the past few hours), PWATs of 2.0-2.3"
(between the 90th percentile and max moving average, per MHX/WAL
sounding climatology), and effective bulk shear of 20-30 kts. A
mid-level shortwave/vort max seems to be providing the necessary
shear to keep convection somewhat organized and longer-lived,
despite other synoptic factors being a bit lacking (though some
upper-divergence is also being provided by the right-entrance
region to a 90-kt jet streak over the Northeast).

Localized rainfall rates have already been capable of 1-3"/hr
rates, and the 12z HREF guidance suggests that these rates will
continue through 21z. Neighborhood (40-km) exceedance
probabilities for 3" and 5" thresholds are relatively high,
between 40-80% and 20-40%, respectively. These are maximized over
southeastern VA, but also extend into portions of northeastern NC
as well. Given that localized amounts of 2-4" have already
occurred, isolated to scattered instances of flash flooding are
considered likely into the afternoon.

Churchill

....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!=
DZ3fjg!7pnKsQ3rUMu4GYgPouQlNY8YZRdnmDsB6V1bP2hVWCgzDPp1bv6QBim2AZ4DhQg5ml-x=
WcHR4K09flEzGpH_yLtfClE$  for graphic product...

ATTN...WFO...AKQ...MHX...RAH...RNK...

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

LAT...LON   38107686 36907567 35697582 35567678 36307793=20
            37227881=20

=3D =3D =3D
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