Flash Flood in Georgia, September 5, 2022

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
1021 AM EDT Mon Sep 5 2022

.SYNOPSIS...
Deep moisture will continue across the area before a weak cold front
drops south by mid week. On Thursday, low pressure sets up over
Louisiana and channels deep moisture and possibly heavy rainfall out
of the Gulf toward the region which will help temperatures below
normal.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 955 AM: Deep and moist southerly flow continues into
the area. A veering trend on KGSP/TCLT VAD profiles has been
evident over the last several hours, more or less as expected in
response to pivoting trough axis over the inland East. Upslope
flow along the Blue Ridge Escarpment, and continued development of
rainfall in that area, remains the primary forecast concern thru
the remainder of the day. As flow continues to veer, the upslope
component still looks to weaken by mid-afternoon, and CAM consensus
remains that the rainfall will become less focused and in general
more intermittent by late day. Models continue to show wide spread
in their depiction of diurnal instability; cloud cover should thin
enough to allow at least a few hundred joules of SBCAPE to develop
by peak heating. Loosely defined shortwave to our northwest may give
a little boost to forcing although the best DPVA will miss us to the
north. While this setup may not be sufficient for more than a token
chance of thunder, it could allow redevelopment of showers. With 2"
or more of PWAT and largely unidirectional profiles, heavy rainfall
and/or training could result. That said, current thinking is that
the Flood Watch is well placed and the 8 pm EDT expiration is
appropriate. By evening, the setup for heavy rain should be more
comfortably in a diminishing trend. Muggy conditions will persist
into evening due to abundant moisture, but temps look on track to
remain below normal because of the widespread precip and clouds.

&&

.SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/...
As of 205 AM EDT Monday...The weather remains unsettled over the
short range period, yet the chance for heavy rainfall and flooding
will go down. A complicated pattern will continue to evolve as the
models show a transition from subTrop ridge dominance to more of a
weak sfc trof and broad frontal zone into the area Tue thru Wed. The
flow off the sfc veers w/ly which will lower mlvl moisture and dry
out the sfc layer in the lee, thus not expecting easily produced
rain showers as has been the case recently the past few days. With
the downslope drying, have kept the better PoPs across the mtns
where tstm development will be more likely as well. The NAM
soundings show low to moderate sbCAPE available, yet shear remains
low-end, likely leading to pulse-type storms or multicell clusters
during max heating. The llvl flow shifts more nw/ly to ne/ly as a
sfc high pushes south behind a weak back-door cold front Thu, yet
sfc td/s remain elevated keeping rather humid conds as max temps
rise a a little abv normal in better insol. Mins shud also remain
elevated by a few degrees due to Ci blow off from the west.

&&

.LONG TERM /THURSDAY THROUGH SUNDAY/...
As of 250 AM EDT Monday...A progressive patten continues thru the
ext range as an upper low closes off across the srn MS Valley and
begins to bring in a good amt of moisture flux along with a stream
of h5 vort energy. The models have varying ideas with the placement
of heavy rainfall, with the ECMWF higlighting the NC mtns and
escarpment regions with arnd 2-3 inches Thu night thru Sat. The GFS
is less sure and keeps the best precip along a more srn cvnvg zone
in a developing sfc wedge, while the CMC indicates a rather dry and
supressed pattern with a 1024 mb sfc high centered over PA by Sat.
So, confidence is a little lagging with the prospects of sigfnt
flooding issues for now, yet this overall setup can certainly make
for a couple days of hydro concerns depending on the alignment of
the upper low and how it eventually gets picked up by the
westerlies. Still expect high cloud cover keeping max temps down and
thunder chances on the low end each day, yet if a CMC type soln pans
out, the wedge bndry would make for a good focusing zone for deep
strong convection each afternoon across the srn and wrn zones.
Confidence will likely increase as we near this event and figure out
the most likely interactions btw the nrn and srn stream systems.

&&

.AVIATION /15Z MONDAY THROUGH FRIDAY/...
At KCLT and elsewhere: Looking grim for Aviation weather over the
next 18 hours or so as a deep and very moist S/SE upslope flow
forces widespread showers that will form at any time. It will
be a mess out there through the morning hours with widespread
inconsistent MVFR/IFR/LIFR ceilings moving across the terminals
as an upper wave carries precip across the region. We will be
in-and-out of showers and light/moderate rain that will likely keep
the vis oscillating between VFR and MVFR for the better part of the
morning at least. This first wave of precip may lift north across
the region by midday. Will spend our TEMPO group this morning to
account for IFR/LIFR restrictions. Unfortunately, there will be
holes in this ceiling...some VFR. The ceiling should rise to MVFR
by midday. The next round as indicated by the CAMS will be in the
late afternoon and early eve, which will be handled with PROB30s. A
brief period of improvement to VFR is possible late in the day or
in the evening, but guidance suggests the ceiling will crash back
down toward IFR late Monday night. Wind will remain light SE to
S through the period.

Outlook: Moisture will remain high as an unsettled pattern appears
likely thru most of the week. There is a decent chance of a lull
in precip with fewer restrictions on Tues and Wed, however moisture
ramps up again by Thurs.

&&

.GSP WATCHES/WARNINGS/ADVISORIES...
GA...Flood Watch until 8 PM EDT this evening for GAZ010-017-018-026-
     028.
NC...Flood Watch until 8 PM EDT this evening for NCZ033-035-048>053-
     058-059-062>065-501>510.
SC...Flood Watch until 8 PM EDT this evening for SCZ101>106-108.

&&

SYNOPSIS...SBK
NEAR TERM...PM/Wimberley
SHORT TERM...SBK
LONG TERM...SBK
AVIATION...PM

Hazardous Weather Outlook
National Weather Service Greenville-Spartanburg SC
510 PM EDT Sun Sep 4 2022

GAZ010-017-018-026-028-NCZ051-052-058-059-062>065-507-509-SCZ101>106-
052115-
Rabun-Habersham-Stephens-Franklin-Hart-Swain-Haywood-Graham-
Northern Jackson-Macon-Southern Jackson-Transylvania-Henderson-
Rutherford Mountains-Polk Mountains-Oconee Mountains-
Pickens Mountains-Greenville Mountains-Greater Oconee-
Greater Pickens-Central Greenville-
510 PM EDT Sun Sep 4 2022

...FLOOD WATCH IN EFFECT THROUGH MONDAY EVENING...

This Hazardous Weather Outlook is for northeast Georgia, western
North Carolina and upstate South Carolina.

.DAY ONE...Tonight.

Please listen to NOAA Weather Radio or go to weather.gov on the
Internet for more information about the following hazards.

   Flood Watch.

.DAYS TWO THROUGH SEVEN...Monday through Saturday.

Please listen to NOAA Weather Radio or go to weather.gov on the
Internet for more information about the following hazards.

   Flood Watch.

.SPOTTER INFORMATION STATEMENT...

Spotter activation may be needed. Please relay any information about
observed severe weather to the NWS while following all local, state,
and CDC guidelines.

GAZ029-NCZ033-048>050-053-501>506-508-510-SCZ010-107>109-052115-
Elbert-Avery-Madison-Yancey-Mitchell-Buncombe-Caldwell Mountains-
Greater Caldwell-Burke Mountains-Greater Burke-McDowell Mountains-
Eastern McDowell-Greater Rutherford-Eastern Polk-Anderson-
Southern Greenville-Northern Spartanburg-Southern Spartanburg-
510 PM EDT Sun Sep 4 2022

This Hazardous Weather Outlook is for northeast Georgia, western
North Carolina and upstate South Carolina.

.DAY ONE...Tonight.

Scattered showers with embedded thunder will develop across the
mountains and foothills of North Carolina this evening. Some of
these storms may produce torrential rainfall possibly leading to
localized flooding. Gusty winds and cloud to ground lightning are the
main potential impacts with this activity.

.DAYS TWO THROUGH SEVEN...Monday through Saturday.

Scattered showers with embedded thunder will develop across the
mountains and foothills of North Carolina again on Monday. Some of
these storms may produce torrential rainfall possibly leading to
localized flooding. Gusty winds and cloud to ground lightning are
the main potential impacts with this activity.

.SPOTTER INFORMATION STATEMENT...

None.

NCZ035>037-056-057-068>072-082-SCZ008-009-011>014-019-052115-
Alexander-Iredell-Davie-Catawba-Rowan-Cleveland-Lincoln-Gaston-
Mecklenburg-Cabarrus-Union NC-Cherokee-York-Abbeville-Laurens-
Union SC-Chester-Greenwood-
510 PM EDT Sun Sep 4 2022

This Hazardous Weather Outlook is for piedmont North Carolina and
upstate South Carolina.

.DAY ONE...Tonight.

Isolated to scattered thunderstorms will develop across the Piedmont
of the Carolinas and northeast Georgia this evening. The main hazard
with any of these storms will be cloud to ground lightning and gusty
outflow winds.

.DAYS TWO THROUGH SEVEN...Monday through Saturday.

Scattered thunderstorms will develop across the Piedmont of the
Carolinas and northeast Georgia again on Monday. The main hazard
with any of these storms will be cloud to ground lightning, gusty
outflow winds, and minor localized flooding from heavy downpours.

.SPOTTER INFORMATION STATEMENT...

None.