AWUS01 KWNH 291124
FFGMPD
NCZ000-SCZ000-GAZ000-TNZ000-291600-

Mesoscale Precipitation Discussion 1002
NWS Weather Prediction Center College Park MD
723 AM EDT Tue Aug 29 2023

Areas affected...Northeast GA...Upstate SC...Western NC...Adj Far
Eastern TN...

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

Valid 291130Z - 291600Z

SUMMARY...A few more hours of slow moving thunderstorms crossing
rugged terrain resulting in possible flash flooding incidents.

DISCUSSION...GOES-E 10.3um and WV suite depict a mature MCV with
active but asymmetric convective cloud tops across the southeast
and eastern side of the wave. The MCV continues to reside in a
favorable mid to upper level divergence pattern aloft to maintain
and perhaps intensify the circulation as it slides slowly
northward; however, the convective environment is eroding into
diurnal minimum as the atmosphere stabilizes a bit in early
morning hours. RAP analysis shows a pocket of remaining uncapped
to weakly capped 1500-2000 J/kg of MUCAPE along the southeast
upwind edge of the complex across northeast GA.

VWP in FFC/ATL and GSP support some 15-20kts of low-level flow
which is weakly convergent allowing for continued thunderstorm
activity across NE GA into Upstate SC and western NC. The upglide
ascent supports some vertical development and given moisture
loading of near 2" (mostly in the lower environment) may still
support 1.5-2"/hr rates. While flow is expected to become more
confluent and less convergent, the steering may allow for
south-southwest to north-northeast training elements across the
lower to mid slopes of the Southern Appalachian mountains.

FFG values are lower across the region, so spots of an additional
2-3" (very isolated 4") may result in a spot or two of flash
flooding through early morning hours, though much should be ending
by 16z, likely recharging for additional development again later
into the afternoon.


Gallina

ATTN...WFO...FFC...GSP...MRX...

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

LAT...LON 36218244 35788183 35068193 34628228 34088313
34088381 34498421 35208424 35698355

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AWUS01 KWNH 300041
FFGMPD
NCZ000-SCZ000-GAZ000-TNZ000-ALZ000-300500-

Mesoscale Precipitation Discussion 1006
NWS Weather Prediction Center College Park MD
840 PM EDT Tue Aug 29 2023

Areas affected...northern GA...northeast AL...adjacent portions of
East TN and far western NC

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

Valid 300035Z - 300500Z

Summary...Isolated instances of flash flooding possible with
1-2"/hr rainfall rates, localized totals of 2-4".

Discussion...Slow moving showers and thunderstorms have developed
in and around the Atlanta metro area, as well as farther north
along portions of the southern Appalachians. The mesoscale
environment is characterized by SB CAPE of 1000-2000 J/kg, PWATs
of 1.7-2.1" (between the 90th percentile and max moving average,
per FFC sounding climatology), and less than 20 kts of effective
bulk shear (with 850-300 mb mean layer flow of 10-15 kts). While
thunderstorm longevity is not expected to last long due to lack of
deep layer wind shear, an outflow boundary that have moved in from
the southeast has been the focus for development through portions
of the north Atlanta metro. The deep layer mean flow is oriented
parallel to this outflow boundary (towards the northeast), which
may allow for some limited training of 1-2"/hr rainfall rates.
Some of this activity may also extend west and north into portions
of northeast AL and adjacent portions of East TN and far western
NC. Isolated instances of flash flooding are possible over the
next several hours, with expected localized totals of 2-4".

Churchill

ATTN...WFO...BMX...FFC...GSP...HUN...MRX...

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

LAT...LON 35938368 35598315 34798315 33818386 33218548
33648689 34218639 35038521 35488443

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