616
FXUS62 KGSP 160200
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
1000 PM EDT Thu Aug 15 2024

.SYNOPSIS...
High pressure will drift off the East Coast Friday as a cold front
approaches from the northwest this weekend, bringing better coverage
of showers and thunderstorms. Drier conditions will return behind
the front as well as near normal temperatures early next week.

&&

.NEAR TERM /THROUGH FRIDAY/...
Evening Update...A rather quiet overnight in store with a broad
p/grad in place keeping winds weak to calm across the FA. Upper
ridging remains strong with only few/sct Ci passing overhead. All in
all good rad cooling with lows dropping to right arnd normal. Not a
great threat for dense fog, but a few locales across the NC mtns may
see VSBY lowering to a half mile or less before daybreak.

As of 245 PM EDT Thursday: Some enhanced cu have been bubbling over
top of the ridges early this afternoon, with some radar returns over
the higher peaks, so that part of the forecast appears to be in good
shape. The latest mesoanalysis shows sfc-based CAPE on the order of
500-1000 J/kg, so a thunderstorm won`t be ruled out, but with poor
lapse rates and shallow profiles, lightning seems unlikely. Still
seeing a patch of remnant cloudiness moving southeast over the
western Upstate and northeast GA, so those locations might be
kept a deg or two cooler than expected. Otherwise, the fcst was
in good shape.

Showers should dissipate this evening with the loss of heating,
without much in the guidance to indicate that any of it would
persist, unlike last night. Could be some mtn valley fog
once again. Low temps should be close to normal. Moving on to
Friday...the sfc ridge that we have enjoyed for the past few days
should slide off to the east as the upper pattern remains slowly
progressive. In this pattern, an upper ridge axis will make slow
eastward progress, moving overhead during the day, thus allowing
upstream moisture and convection to make a run for our borders. Most
of the guidance has a weak short wave helping to organize some
convection upstream during the day, then driving it east or
southeast toward us with varying degrees of success, probably
because of instability east of the mtns by Friday afternoon. Over
the mtns looks like no problem, with a general agreement that we
should destabilize to the tune of 1000-2000 J/kg of CAPE in the
afternoon, but east of the mtns, not so much. That will be the
limiting factor as to whether or not any convective outflows can
trigger storms into the Piedmont late in the day. One or two of
the CAMS do just that, so precip probs will be extended a bit
further east than shown in the synoptic guidance. However, the
main threat will be on the west side of the mtns for any strong
linear convection that can survive through the TN Valley and not
dive off to our southwest. High temps will be close to normal.

&&

.SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY/...
As of 225 PM EDT Thursday: A long wave trough builds over the East
Coast through the period as an upper low traverses the Great Lakes
and a series of short waves cross our area in the developing trough.
An associated cold front slowly moves into the area Saturday then
across the area Sunday. A moderately unstable air mass is expected
to develop Saturday and continue into Sunday. Around 30 knots of
bulk shear is expected both days as well. Despite PW values
approaching 2 inches, there is mid level dry air with quite a bit of
dCAPE and sfc delta theta-e. SPC currently has us in a Marginal Risk
of severe storms, and this looks reasonable. Sunday is a little more
uncertain and there could be less overlap of instability, shear,
and mid level dry air. Locally heavy rainfall is also possible both
days. Temps will be near to slightly above normal Sunday and near to
a few degrees below normal Monday.

&&

.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
As of 155 PM EDT Thursday: The medium range guidance shows the deep
long wave trough over the East Coast now lingering through Tuesday
as a series of short waves move through the trough Monday and
Tuesday. The trough slides east Wednesday with a weak ridge
beginning to move in from the west Thursday. At the surface, enough
low level moisture remains over the area Monday with a front stalled
along the coast for scattered diurnal convection mainly over the
mountains dropping off to isolated across the NC Piedmont. Drier air
moves in for Tuesday and Wednesday ending the convective threat.
Moisture return begins again on Thursday to increase the potential
of isolated to scattered diurnal convection, but the day could end
up dry if the moisture return is slower. Temps will be a few degrees
below normal through the period.

&&

.AVIATION /02Z FRIDAY THROUGH TUESDAY/...
At KCLT and elsewhere: A quiet evening is in store with little
chance of showers at any TAF site with VFR conds continuing into the
overnight. Before daybreak, KAVL and KHKY could see IFR/MVFR VSBY
respectively as guidance has trended down due to good rad cooling
and calm winds expected. Afternoon showers and thunderstorms will be
most likely at KAVL as an upper disturbance pushes in from the west.
However, some indications are showing KHKY possibly seeing tstms by
the later afternoon as well. Kept a VCSH at KCLT aft 22z as there
remains some uncertainty to storm strength and coverage with the
incoming convec activity. Winds remain rather weak thru the period
with a general s/ly to sw/ly direction at all TAF sites.

Outlook: A cold front will track over the forecast area this weekend
keeping convection around. Drier conditions return behind the front
early next week. Patchy fog and low stratus will be possible each
morning 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...DEO
NEAR TERM...PM/SBK
SHORT TERM...RWH
LONG TERM...RWH
AVIATION...SBK