Subj : MESO: Nws Weather Prediction Center College Park Md
To   : wx-storm@lists.illinois.edu
From : COD Weather Processor
Date : Thu May 18 2023 17:21:49

AWUS01 KWNH 181721
FFGMPD
SCZ000-GAZ000-182300-

Mesoscale Precipitation Discussion 0310
NWS Weather Prediction Center College Park MD
121 PM EDT Thu May 18 2023

Areas affected...Southern SC...Eastern and Southeast GA...

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

Valid 181720Z - 182300Z

SUMMARY...Widely scattered, efficient, slow moving shallow
thunderstorms continue in proximity to southern stream
shortwave/boundaries. Widely scattered totals of 3-5" along the
coast may pose rapid inundation flooding solely in urban
locations.=20

DISCUSSION...GOES-E Visible imagery continues to denote the slow
ENE motion of the shortwave, now over southeast GA, with continued
diffluence within the entrance to 40kt 300mb jet across Upstate SC
into NC. The combination continues to support boundary layer to
850mb cyclone near AGS with increasing easterly flow/moisture flux
along/north of the boundary layer front extending eastward toward
the developing surface low over the Gulf Stream.  Weak isentropic
ascent and minimal instability has maintained shallow, but
efficient showers near the 850mb low and will continue a very
isolated risk for localized heavy rainfall up to 2-3" and possible
flash flooding, particularly nearer lower FFG values and August
metro proper.

Filtered insolation has increased some surface heating near the
lower Savannah River Valley resulting in modest but narrow axis of
SBCAPEs, expanding due to warmer Atlantic waters across the
coastal counties with similar 1500+ J/kg values.  Strongest
convergence remains at the intersection of the boundary layer
frontal zone and will continue to drop southward with north to
easterly convergence along and just offshore.  Sfc-1km helicity
has been strong enough to support rotating updrafts and enhanced
moisture flux for cells to allow for 2-3"/hr rain rates throughout
the morning, and is likely to continue as the forcing/axis slide
south. Bunkers right moving propagation vectors suggest less than
5kts of forward speed with the weakly rotating updrafts resulting
in pockets of 3-5" possible.   As such, rapid inundation flooding
will remain possible mainly for urban locations east of I-95
through the next 4-5hrs.

Gallina

....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!=
DZ3fjg!_EbGApd-ODLhWnsj-tGjmm03ih6kr9UpR7iy6HoesXgX5JTc1UtAEjd5iO7Opwo31C7L=
hp8tJLUvKHJscqSGdm2GNgU$  for graphic product...

ATTN...WFO...CAE...CHS...FFC...ILM...JAX...

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

LAT...LON   33818190 33578125 33258086 33228012 33437956=20
            33427911 33277889 32987921 32597988 32178064=20
            31788111 31418131 31438180 31938238 32368276=20
            32868304 33318310 33798268=20

=3D =3D =3D
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