502
FXUS62 KGSP 131338
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
938 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/...
     Key Messages...

1) Numerous Showers east of the Blue Ridge with Isolated
Thunderstorms Possible this morning

2) Isolated Strong to Severe Storms Possible this Afternoon and
Early Evening, mainly east of the mountains

3) Cooler Temperatures Expected Today

As of 930 AM EDT Tuesday: Updated the precip probs over the Piedmont
based on the ongoing numerous showers and embedded thunderstorms,
mainly to raise into the likely range. So far, the activity has
been relatively benign, but some of the precip rates have been on
the order of 2 in/hr in the stuff that moved over Greenville, which
resulted in some quick response on a few of the creeks. Fortunately,
the convection is plodding along just fast enough to keep amounts
in check. The precipitable water is relatively high, so the main
concern will be duration, if the cell orientation leads to training
over any particular area. Once this activity finally pushes off
to the east, the CAMs are showing some redevelopment during the
afternoon.  That`s the stuff that could be a problem in terms of
stronger storms.

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. Although deep layer shear will range from
35-45 kts, lapse rates look relatively poor and the sfc-based CAPE
might make it to around 1500 J/kg during peak heating. The SPC Day
1 update kept the Marginal Risk over the eastern Piedmont of SC
(south of CLT) today. Damaging wind gusts will be the main concern
with any severe storms that develop. The excessive rainfall threat
will remain isolated with higher shear values in place allowing for
faster storm motion. 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 the recent rainfall
over the weekend. Convection should gradually end from west to east
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 /14Z TUESDAY THROUGH SATURDAY/...
     Key Messages...

1) Scattered Morning Showers with Isolated Thunderstorms Possible
for TAF Sites East of the Mountains

2) Scattered Showers and Thunderstorms Return this Afternoon for All
Terminals

3) Generally MVFR/VFR Conditions Expected for Most Terminals

At KCLT and elsewhere: 12Z TAF period will remain fairly active at
least through today. A broken line of showers has develop along and
east of the western North Carolina mountains this morning and
continues pushing east. Have TEMPOs for -SHRA for all terminals east
of the mountains through the morning hours. KAVL will most likely
stay dry through the morning hours 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.
Scattered showers and thunderstorms are expected to develop this
afternoon and evening so have TEMPOs 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. KAVL will likely
see light and VRB winds tonight as well as the potential for patchy
fog. Patchy fog may reach KHKY but confidence on this is low for
now. Drier conditions will filter into the region from west to east
later this afternoon into this evening, continuing into Wednesday
morning.

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