135
FXUS62 KGSP 130725
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
325 AM EDT Tue Aug 13 2024

.SYNOPSIS...
Dry high pressure gradually builds in from the north through
Thursday, pushing a stalled front further south of the area. The
high will drift east off the East Coast Friday, as a cold front
approaches from the west over the weekend. The front will bring
a return of better chances of shower and thunderstorms.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 300 AM EDT Tuesday: Already seeing some scattered showers
developing along the Blue Ridge Escarpment and the northern NC
Foothills this morning. Coverage is expected to expand through the
morning hours while pushing east per the 00Z CAMs. A few isolated
thunderstorms cannot be entirely ruled out but instability should
remain low through daybreak. Areas in the North Carolina mountains
west of the Blue Ridge should see dry conditions prevail through the
morning hours. With cloud cover expected to linger (and increase)
through daybreak, lows will end up around 2-4 degrees above climo.
Cloud cover should limit mountain valley fog formation somewhat but
patchy fog may still develop.

Otherwise, upper troughing will remain over the Carolinas through
the near term while periodic shortwaves track over the region from
the northwest. Meanwhile at the sfc, the southern periphery of
surface high pressure centered over the Great Lakes region will
extend into the Carolinas while a front stalls over the Southeast.
This will lead to a more convectively active day compared to
yesterday. 00z CAMs show scattered convection firing over the
mountains by the early afternoon hours, gradually spreading east
through rest of the afternoon and early evening. Although deep shear
will range from 35-45 kts today, 00Z HREF ensemble probability shows
less than 2,000 J/kg of CAPE across the forecast area through the
period. However, the 00Z CAMs show the potential for 1200-1500 J/kg
of CAPE across the southern zones during peak heating. The SPC Day 1
Severe Wx Outlook shows a Marginal Risk for isolated severe storms
across the eastern SC Upstate and the southern NC Piedmont (south of
CLT) today. This looks reasonable as the far southeastern zones have
the best chance to see cloud cover breakup briefly this afternoon,
allowing for better destabilization. The excessive rainfall concern
should remain isolated with higher shear values in place today
allowing for faster storm movement. However, flash flood guidance
continues to be on the low side (mainly across the eastern two-
thirds of the CWA) due to the rainfall from Debby last week and
rainfall over the weekend. Convection should gradually end from west
to east late this afternoon into this evening, with drier conditions
moving in tonight. Temperatures this afternoon will be much cooler
compared to yesterday. However, highs will remain a few degrees
above climo across the Little TN Valley and the Upper Savannah River
Valley. Highs elsewhere should end up a few to several degrees below
climo thanks to higher cloud cover. Lows tonight will end up near
climo to a few degrees above climo. Patchy fog may develop across
the NC mountains and Foothills overnight into daybreak Wednesday.

&&

.SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
As of 145 AM EDT Tuesday: The short term looks fairly quiet, as the
axis of a deep upper trough will swing east off the East Coast,
and upper ridging builds in from the Lower Mississippi Valley
Wednesday thru Thursday. At the sfc, dry air will filter in from
the north, limiting instability. A light easterly or southeasterly
low-level flow may be enough to force a few isolated showers and
perhaps a garden-variety tstm or two Wednesday and Thursday aftns
in the mountains, but otherwise, it should be partly cloudy with
temps slightly below normal. Highs in the mountain valleys and
Piedmont will be mainly in the low to mid 80s and lows in the mid
to upper 60s.

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
As of 230 AM Tuesday...The medium range guidance is in good
agreement on a vigorous shortwave diving thru the western Great
Lakes Friday, carving out a fairly deep upper trough across the
Ohio Valley Saturday, then persisting as a long wave trough across
the eastern CONUS into early next week. An associated low pressure
system will bring a cold front into the Ohio Valley and possibly
crossing the forecast area over the weekend. The front is expected
to stall out roughly across the Midlands or Coastal Plain Sunday or
Monday. Overall, the front will have limited moisture to work with,
but should support scattered to numerous showers and thunderstorms
in the NC mountains with help of NWLY upslope flow Friday and
Saturday. Downsloping east of the mountains may limit coverage,
but support a return of near-normal to slightly above-normal
temps. Drier air filters in behind the front Sunday into Monday,
lowering PoPs and bringing temps down a couple degrees.

&&

.AVIATION /08Z TUESDAY THROUGH SATURDAY/...
At KCLT and elsewhere: 06Z TAF period will be rather active as CAMs
show the potential for scattered convection developing in the next
few hours and lingering through potentially mid-morning. Thus have
TEMPOs for -SHRA through the morning hours east of the mountains.
KAVL will likely stay dry through daybreak but have a TEMPO for MVFR
cigs and fog around daybreak. KHKY could see IFR cigs develop by mid-
morning so have this accounted for in a TEMPO. Elsewhere generally
MVFR to VFR cigs and vsbys are expected through the period outside
of convection. Scattered showers and thunderstorms are expected to
develop this afternoon and evening so have PROB30s for -TSRA at all
terminals to account for this activity. Wind direction will remain
N/NE east of the mountains through the TAF period. Winds at KAVL
will be calm to light NW through daybreak before turning more E/NE.

Outlook: Expect mostly diurnal isolated to scattered diurnal
convection through Thursday. Coverage of convection increases Friday
into Saturday as a cold front approaches out of the west. Patchy fog
and low stratus will be possible each night in the mountain valleys
and in any locations that received heavy rainfall the day prior.

&&

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

&&

$$

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