Clarkesville, Georgia Weather Forecast Discussion

424
FXUS62 KGSP 201023
AFDGSP
Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
623 AM EDT Sat Sep 20 2025
.SYNOPSIS...
Pop up showers and thunderstorms are possible in northeast Georgia
and the western Upstate today, and across parts of the mountains
each day through Tuesday. Temperatures remain at or slightly
above normal for this time of year. Unsettled weather and cooler
temperatures develop in the second half of next week.
&&
.NEAR TERM /THROUGH TONIGHT/...
As of 135 AM EDT Saturday: A weak ridge slides overhead as an upper
low lifts northward over the Midwest. Overnight, guidance shows a
weak shortwave crossing the Tennessee Valley with lingering DPVA
over a portion of the CWA through the morning hours. Guidance
maintains a steady 1-1.5 inch range of PWATs across the entire CWA
through the end of the period. During Saturday afternoon, few
isolated showers and thunderstorms are possible over the mountains.
CAM guidance from the HRRR initiates a few small storms during the
afternoon hours and into the evening, starting in the mountains and
spreading into Upstate SC and NE Georgia. Nothing severe is
anticipated, however locally heavy rain and strong winds are
possible wherever storms can initiate. Unlike Friday, an increase in
westerly winds aloft should help steer these storms and reduce the
flash flood risk. There is a higher amount of instability as well.
For this, will keep PoPs at slight chance for far western NC
mountains and Upstate SC/NE Georgia. Any convective activity that
occurs should quickly wind down Saturday night and remain quiet
through the rest of the period. As for temperatures, the ridge axis
moves out of the area, slightly decreasing heights. This should tick
down the daytime temps into the upper 80s outside the mountains.
&&
.SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/...
As of 1205 AM Sat: Subtle ridging is seen at 500 mb on Sunday between
the departed southern-stream shortwave and the phased trough moving
thru the central CONUS. Sfc high pressure remains in place over the
Southeast states. Lapse rates over the CWA continue to be markedly
poorer compared to Saturday, although true capping is now only noted
over the eastern zones. Deep convection appears a little more
plausible than it did on yesterday`s runs. As such PoPs have crept
upward over the mountains primarily SW of the French Broad.  CAMs are
not in great agreement as to convective coverage so confidence is
low, warranting low chances at best. The limited SBCAPE suggests
resulting convection probably will be showers, but a garden-variety
storm can`t be ruled out. With low-midlevel SW flow developing ahead
of the next trough, PWATs appear likely to increase marginally during
the day.  Storm motion will remain slow, offset by still easterly to
SE`ly sfc winds, so locally heavy rain could result from the stronger
cells. Temps will trend a little cooler, briefly, but still about 2-4
above normal.
Heights do technically fall a bit for Monday, but there is not much
dynamic forcing of note with the trough this far south. The
associated weak sfc/upper cyclone will be north of the Great Lakes
and the only vort energy appears to be with convection along a very
weak frontal zone extending down into the Ohio Valley, i.e., west of
the Appalachians and likely of little direct impact to us at that
time.  Diurnal forcing and ridgetop convergence are the primary
justification for PoPs; PWATs don`t change much but SBCAPE should
trend slightly higher on account of marginally better lapse rates and
warmer sfc temps. Precip chances remain over the mountains but
increase to 30-40% over most areas northwest of the Blue Ridge
Escarpment. Similar potential for locally heavy rain. Elevated
convection may continue in the Great TN Valley Monday night and it is
not out of the question some of that may brush along the TN/NC
border, and/or a few cells may fire near the border during the
evening, so small PoPs carry on after 00z in the Smokies.
&&
.LONG TERM /TUESDAY THROUGH FRIDAY/...
As of 1250 AM Sat: The parent low of the Ohio Valley front looks to
reach the Canadian Maritimes Tuesday morning, being driven mainly by
a trough digging east of Hudson Bay. The front itself will languish
to our west on Tuesday, resulting in little meaningful change to our
weather compared to Monday. Regardless of the specific evolution from
that point, the progress of the front remains slow thru the rest of
the forecast period but the net result looks to be a period of
widespread unsettled weather in the second half of next week.
The major global models appear to be trending toward an expansive
cutoff low developing in the Mississippi Valley by Thursday or early
Friday, though there are differences in timing and the position of
such a low. Accordingly the onset of forced/non-diurnal precip
varies, but chances expand across the whole area by late Wed and
remain at high-chance to likely values Thu through Fri.  The
position/track of the upper low would appear to determine the
intensity of precip and in particular whether we have potential for
warm-sector convection, which could translate to severe risk.
Confidence remains low on these points. The warming trend continues
thru Tue in the mountains and thru Wed in the Piedmont, with temps
then trending below normal as precip/clouds increase, and/or as CAA
develops once the front and/or low settle through.
&&
.AVIATION /12Z SATURDAY THROUGH WEDNESDAY/...
At KCLT and elsewhere: VFR conditions prevail at most sites for the
TAF period. SKC for terminals east of the mountains and calm/VRB
winds to start the period. BR/fog started early at KAVL and should
clear up after 13z. Winds continue to be VRB and light through
Saturday afternoon. Will go ahead and prevail northerly winds at
KCLT until this evening when the winds turn more ENE. There is a
slight chance for TSRA and showers at a few terminals including KAVL
and KGSP. For now, a PROB30 at those terminals and KAND/KGMU. KCLT
should remain dry. Tonight, another round of BR/FG expands to KAVL.
There is a possibility for IFR vsby at KHKY as well but confidence
is too low to mention at this time.
Outlook: Dry weather returns to start the week. Rain chances may
return Tuesday thru midweek. Fog and stratus possible each morning
in the mountain valleys.
&&
.GSP WATCHES/WARNINGS/ADVISORIES...
GA...None.
NC...None.
SC...None.
&&
$$
SYNOPSIS...Wimberley
NEAR TERM...CP
SHORT TERM...Wimberley
LONG TERM...Wimberley
AVIATION...CP

NWS GSP Office Area Forecast Discussion