273
FXUS62 KGSP 121753
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
153 PM EDT Mon Aug 12 2024

.SYNOPSIS...
A stalled frontal boundary over the Carolinas may lead to isolated
showers and thunderstorms this afternoon and evening. High pressure
builds in throughout the workweek while the front stalls over the
Southeast and keeps daily shower and thunderstorm chances around.
High temperatures will continue on a cooling trend through the
workweek, with a warming trend expected over the weekend ahead of an
approaching cold front.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 145 PM EDT Monday: Morning clouds have thinned out as
expected, and temp trends also appear to be working out. Nice
dewpoint gradient from N to S across the region, more or less as
expected. A fairly quiet afternoon is planned, with maybe the chance
for something to fire up on the southern slopes of the Balsam mtns,
which some of the guidance continues to do. No changes yet.

Otherwise...a broad upper trough axis will persist roughly along
the Appalachians, while weak sfc high pressure builds into the
Ohio Valley. The high may work to try to nudge a stationary front
south slightly from where it`s been the last couple days. Temps
are expected to be similar to yesterday`s highs, near normal in
the northwest Piedmont, and a category above normal in the Upper
Savannah Valley.

Tonight, a vigorous shortwave will dive SE across the Ohio Valley,
helping dig the longwave trough over the region. The approaching
wave will help increase MUCAPE and may trigger some elevated
convection across the forecast area overnight. The 00z HRRR
is most bullish with thunderstorms forming roughly across the
I-26 corridor after midnight then spreading east thru daybreak
Tuesday. The other CAMs hint at some overnight convection, but
look like mainly scattered showers. All of the op models also have
some QPF response by 12z Tuesday in these areas. Will allow for
some slight chc PoPs overnight, which may be bumped up in future
updates if the model trends hold. Temps will be near normal under
increasing clouds overnight.

&&

.SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/...
     Key Messages...

1) Isolated Strong to Severe Storms Possible Tuesday

2) Severe threat will be Lower Wednesday

3) Cooler Temperatures Linger through the Period

As of 200 AM EDT Monday...No major changes to short term. Upper
troughing will remain in place through the period while periodic
shortwaves track across the forecast area from the northwest. At the
sfc, high pressure will expand from the Great Lakes region into the
Carolinas while a front stalls over the Southeast. This pattern will
allow daily scattered showers and thunderstorms to continue. The
best instability on Tuesday looks to remain south of the forecast
area although the 00Z global models and CAMs show the potential for
1000-1800 J/kg of SBCAPE across the southern half of the forecast
area during peak heating. With deep shear expected to range from 35-
45 kts could not rule out the potential for a few isolated strong to
severe storms, especially across the far southeastern zones. The SPC
Day 2 Severe Wx Outlook has a Marginal risk place across the
southern NC Piedmont (south of Charlotte) and the eastern SC
Upstate, which looks reasonable. Deep shear will remain around 35-45
kts on Wednesday but instability will be considerably lower. Thus,
the severe weather threat looks lower on Day 3. Any hydro issues
should remain limited through the short term due to the higher shear
values allowing for faster storm motion. Highs look to be a few
degrees below climo each afternoon everywhere except the Upper
Savannah River Valley and the Little TN Valley where highs should
end up near climo to a few degrees above climo. Lows will remain
near climo to a few degrees above climo through the period.

&&

.LONG TERM /THURSDAY THROUGH SUNDAY/...
     Key Messages...

1) Severe Threat Remains Low on Thursday with Another Round of
Scattered Storms Expected

2) Better Coverage of Showers and Thunderstorms Friday into the
Weekend Thanks to a Cold Front

3) Cooler Temps Continue on Thursday Before a Warming Trend Returns
Friday into the Weekend

As of 230 AM Monday...Upper troughing with embedded shortwaves
tracking over the forecast area from the northwest will continue
Thursday into Thursday night. Friday brief upper ridging builds in
across the Southeast before pushing offshore early Saturday morning.
Another upper trough will dig across the Southeast on Saturday,
lingering over the region through rest of the weekend. At the sfc,
high pressure will gradually track eastward from the Ohio Valley
into the Northeast Thursday into Friday, with the southern periphery
of the sfc ridge continuing to extend across the Southeast. The sfc
high will push offshore into the western Atlantic Friday into
Saturday as a cold front approaches out of the west. The front
should track across the Carolinas and northeast Georgia late
Saturday into early Sunday. Scattered shower and thunderstorms
return again on Thursday, with the severe storm potential remaining
low. Hydro issues will once again be offset by 25-35 kts of deep
shear. Better coverage of showers and thunderstorms returns to the
area Friday into the weekend ahead of and along the cold front. 00Z
global models disagree on if there will be enough instability for
strong to severe storms during this timeframe, so confidence is low
regarding the severe potential. Guidance also shows the potential
for lower shear despite the front which could lead to slower storm
motion and perhaps increase the excessive rainfall threat. However,
with this being towards the end of the forecast period, confidence
will also be low concerning any hydro issues. Highs on Thursday will
be a few degrees below climo area-wide. With a warming trend
expected Friday into the weekend, highs will end up a few degrees
above climo in the Little TN Valley and the Upper Savannah River
Valley with highs elsewhere remaining a few degrees below climo to
near climo. Lows will remain a few degrees above climo through the
period.

&&

.AVIATION /18Z MONDAY THROUGH SATURDAY/...
At KCLT and elsewhere: Clouds have thinned out for the most part
across the region early this afternoon, except for a few patches of
mid-level stuff over the mtns and near the Fall Line. An MVFR deck
persisted over the Savannah R basin at issuance time, but think
that will be mixed out in very short order, so no restriction was
carried at KAND. Thus...VFR at all terminals through late tonight,
when things get interesting. KAVL is expected to have its usual
mtn valley low stratus/fog in the pre-dawn hours. Elsewhere, the
combination of favorable weak upslope flow and the arrival of a
weak upper disturbance is expected to trigger showers and a few
storms near the Blue Ridge around daybreak, and then moving out
east of the mtns into the afternoon. Thus, we include a PROB30 at
all terminals for the time being, starting in the mid/late morning,
but there is a possibility that it could begin as early as 11Z. The
restrictions will be kept in the PROB30.

Outlook: Expect generally isolated to scattered diurnal convection
across the region each day through the work week. Patchy fog and
low stratus will be possible each night in the mountain valleys
and in locations that receive rainfall.

&&

.GSP WATCHES/WARNINGS/ADVISORIES...
GA...None.
NC...None.
SC...None.

&&

$$

SYNOPSIS...AR
NEAR TERM...ARK/PM
SHORT TERM...AR
LONG TERM...AR
AVIATION...PM