203
FXUS62 KGSP 090602
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
202 AM EDT Fri May 9 2025

.SYNOPSIS...
A cold front crosses the area Friday and stalls over the Southeast
this weekend into early next week, keeping unsettled weather around
through then. The front and associated low pressure system finally
clears the area Thursday.

&&

.NEAR TERM /THROUGH TODAY/...
As of 1209 AM EDT Friday: Storms have finally started to developed
across the Upstate, as the HRRR has been advertising. There is
still up to 1000 J/kg of MUCAPE and 35-40 kt of effective shear,
which is even for supercell structures. Low-level shear may be
just enough for a non-zero tornado threat, but overall, large hail
and damaging wind gusts remain the primary threats. And even then,
those threats should continue to diminish with decreasing buoyancy
overnight. Have allowed the Severe Thunderstorm Watch expire.

Otherwise...The cold front to the northwest of the area will
struggle to reach the CWA until Friday afternoon as the upper-level
pattern amplifies with the trough developing a closed upper low and
slows down the frontal boundary advancement. As a result, lingering
convection will be possible overnight as model guidance struggle
to fully get rid of elevated CAPE and overall forcing. Convective
debris will likely linger through much of the nighttime period,
but if some clearing can get going expect areas of fog and possibly
low stratus to settle in just before daybreak.

The now closed upper low will intensify and set up over the Mid-
Atlantic by Friday as the front gradually enters the CWA from the
northwest by late morning to early afternoon Friday. Another round
of convection is expected ahead of the front during peak heating
Friday. CAMs are not as excited with this potential but still show
an environment conducive for multi-cellular to supercellular storm
mode as 25-35 kts of shear and 1000-2000 J/kg of MLCAPE develop. The
overall forcing isn`t the best, however, inverted-v profiles and
dry mid-level indicate damaging winds will be the main threat, but
large hail can`t be ruled out. Coverage will be isolated compared
to today, but a low severe threat will be possible nonetheless as
the cold front moves across the area during peak heating on Friday.
Afternoon highs will end up a few degrees above normal ahead of
the front, but cooler than normal for locations behind the front
(mainly across the mountains) during peak heating.

&&

.SHORT TERM /TONIGHT THROUGH SUNDAY/...
As of 200 PM EDT Thursday: Any left over convection will quickly
dissipate with loss of heating Friday evening as drier and cooler
high pressure builds in from the north and the frontal boundary
moves south of the area. Lows now look to drop to near or 5 degrees
below normal.

Guidance continues to trend drier for Saturday as the drier air mass
and surface high penetrate farther into the Southeast. Even with
those expectations, there may be some showers over the Lakelands
into the Upper Savannah River Valley as moisture may try to lift
north over the stalled frontal boundary. Even if that occurs, any
precip will be very light. Despite the cooler air mass, the lack of
precip will allow temps to warm more than previously expected as no
real cold air damming develops. Highs will still be around 5 degrees
below normal.

This drier trend continues into Sunday with precip slower to move
back north as the moist low level flow and isentropic lift take
longer to develop in response to the developing upper low and
associated surface low near the Gulf Coast remaining farther south
and west of the area. Still have a chance of showers moving into NE
GA and the Upstate by afternoon with slight chance over NC. But
again, any precip would be light. The lack of precip keeps the CAD
from forming and allowing temps to warm more than previously
expected. Didn`t go full on with the model blend given the
uncertainty, but highs end up around 5 degrees below normal but
could be warmer if the precip remains slow to develop.

&&

.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
As of 230 PM EDT Thursday: Widespread precip does begin moving back
into the area Sunday night as the stacked low pressure system begins
moving north and a stronger, moist low level southerly flow and
isentropic lift develop. This does help the hybrid cold air damming
to set in by Monday and holding on through Monday night as precip
continues. The CAD erodes Tuesday as the high moves well off shore
cutting off support for the CAD and the stacked lows move north and
east. Widespread precip remains over the area though with the
strong, moist southerly flow and isentropic lift. The lows only
slowly move northeast on Wednesday keeping moisture and precip over
the area through the day. The lows finally move northeast of the
area on Thursday, but some lingering NW flow showers may continue.

There is a threat of moderate to heavy rainfall with this system.
The guidance has poor run to run consistency of QPF however. In
fact, overall precip will likely be on the lower side of guidance
given the now drier short term. Still, some excessive rainfall and
minor flooding can`t be ruled out. There will be some thunderstorms
once the CAD erodes, but chance of severe storms looks quite low for
now.

Highs will be around 10 degrees below normal Monday in the CAD, then
slowly warming to near normal by Wed and above normal by Thursday.

&&

.AVIATION /06Z FRIDAY THROUGH TUESDAY/...
At KCLT and elsewhere: Convection will linger across the area
thru about 9z, and should mainly be SHRA with isolated TS. Plenty
of debris cloudiness will help slow down fog and low stratus
formation, but with moist ground from evening rainfall, there will
likely be IFR restrictions at all or most of our TAF sites before
daybreak. The fog and stratus should improve mid to late morning
to VFR. A cold front will push into the area from the NW and is
expected to trigger isolated to widely scattered convection as it
crosses the Piedmont. The latest guidance trended lower on coverage,
but will continue with PROB30 for TSRA at KCLT and KGSP/KGMU,
where the chances will be highest. Will go with SHRA at KAVL and
KHKY, which will see the front move thru earlier in the day when
there will be less instability. Winds will shift to WNW at KCLT
and KHKY, but remain WSW in the Upstate until this evening, when
all sites toggle to NE.

Outlook: Brief drying Friday night into Saturday. Then, an
unsettled pattern returns Saturday night thru early next week,
with chances for showers and thunderstorms around as well as
associated restrictions.

&&

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

&&

$$

SYNOPSIS...RWH
NEAR TERM...ARK/CAC
SHORT TERM...RWH
LONG TERM...RWH
AVIATION...ARK