179
AWUS01 KWNH 041220
FFGMPD
VAZ000-NCZ000-SCZ000-GAZ000-041800-

Mesoscale Precipitation Discussion 0218
NWS Weather Prediction Center College Park MD
820 AM EDT Sat May 04 2024

Areas affected...Northeast GA...Upstate SC...Western & Central
NC...far South-Central VA...

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

Valid 041220Z - 041800Z

SUMMARY...Slow moving, narrow, but intense updates with occasional
collisions/mergers pose a few incidents of widely scattered and
localized flash flooding possible this morning.

DISCUSSION...GOES-E WV depicts a elonaged shortwave lifting out of
eastern AL into N GA with mid-level ridge axis poking through the
central Carolinas.  Confluent deeper moisture streams from the
Gulf and return moisture out of the western Atlantic meld through
depth along and just NW of the Fall-line in the central Piedmont
from E GA through south-central VA.  Enhanced deep layer moisture
reaches over 1.5" and nears 1.75" with best solid low level
moisture in place along the I-85 corridor from Anderson-Greenwood,
SC to Greensboro, NC.  While potentially allowing for more
efficient rainfall production, the moist environment has limited
steeper lapse rates for greater mid-level instability to be
tapped. Yet, there appears to be sufficient 500-750 J/kg through a
similar axis along the southeast gradient of the moisture axis.

The approaching shortwave is providing some broad DPVA along and
just northeast of its advancement, but also increasing low level
flow from 5-10kts to 10-20kts by mid-morning to focus on
increasing confluence downstream into NC/S VA.  Deep layer
steering is going to be more limited further from the
short-wave/deeper into the shortwave ridging... so some stationary
nature, even slight retrograding responding to the approaching
height-falls can be expected.

As such, any thunderstorms that do develop are likely to struggle
to maintain strength and may be more pulse-like in nature but will
have intense local downdrafts capable of 1.5" in short-duration.
Resultant outflow boundaries should allow for collisions and aid
to generate the next updraft cycle.  As such, locally intense
sub-hourly to hourly totals of 1.5-2.5"/hr are possible and with
collisions/slow motions may result in localized 3" totals.  So
while most of the area within the MPD is NOT likely to see intense
rainfall, there will be widely scattered (maybe regionally
clustered) ares that may see spotty flash flooding conditions,
especially if the downdrafts fall on urban centers or
traditionally poor drainage areas near the Fall-line and lower
eastern slopes of the Appalachians.

Gallina

...Please see www.wpc.ncep.noaa.gov for graphic product...

ATTN...WFO...CAE...FFC...GSP...RAH...RNK...

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

LAT...LON   36838010 36567886 35767903 34688010 33408171
            32368268 32518353 33348387 33918451 34868355
            35478272 36178140