380
FXUS62 KGSP 080457
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
1257 AM EDT Wed May 8 2024

.SYNOPSIS...
A summerlike weather pattern lingers through mid-week leading to
mainly diurnal showers and thunderstorms and above normal
temperatures. Showers and thunderstorm activity will become more
numerous ahead of a strong cold front tonight into Thursday, with
severe storms possible. The cold front pushes east early Friday
morning but another system approaching out of the south may bring
shower and thunderstorm chances back again on Friday. Drier
conditions and below normal temperatures return just in time for the
weekend.

&&

.NEAR TERM /THROUGH TODAY/...
As of 100 AM EDT Wednesday: Dry conditions are noted across much of
the forecast area this morning, although a few isolated showers have
pushed east into extreme NE GA. Widespread upper cloud cover
continues to fill in across the forecast area this morning, so this
may act to limit fog formation somewhat across the NC mtns and
Foothills. Updated PoPs based on the latest radar trends this
update, and also tweaked PoPs through the duration of the near term
based on the latest CAM guidance. Otherwise, the rest of the
overnight should be fairly quiet with only a small collection of
showers expected to develop over the mtns and Foothills, with maybe
a brief embedded thunderstorm or two. Lows this morning will end up
around 15 degrees above climo thanks to cloud cover and SW`ly flow.

Upper ridging over the Appalachians will breakdown and shift
offshore this afternoon with a highly perturbed southwest flow
regime setting up from the Lower Mississippi Valley into the
Southern Appalachians. This will keep an active period of weather
around through the near term. A residual elevated mixed layer will
advect into the area today, acting to keep the atmosphere capped
through the early afternoon hours. However, with time, increasing
forcing for ascent and surface heating should erode the cap and
allow for thunderstorm development. Considerable spread was noted in
the high-resolution CAM guidance as to when/where storms will
develop. The greatest coverage is expected across the mountains
initially with scattered storms into the foothills. As the afternoon
progresses, activity will likely spread across much of the area
along and north of I-85. The atmosphere will be primed for severe
weather with 3000-4000 J/kg of surface-based CAPE, 6.5-7 C/km mid-
level lapse rates, and 30-40kts of deep-layer vertical wind shear.
This would be supportive of large hail and damaging winds with the
wind threat becoming dominant/more widespread should convection
organize into linear segments. As such, the expansion of the slight
risk from SPC appears warranted. Temperatures this afternoon will be
the warmest of the week, with highs climbing into the mid to upper
80s in the mtn valleys and east of the mtns. Areas near the
Charlotte Metro may even see highs reach the lower 90s. Thus, highs
will remain around 10-13 degrees above climo.

&&

.SHORT TERM /TONIGHT THROUGH FRIDAY/...
As of 215 PM EDT Tuesday: CAMs show the potential for a couple of
rounds of convection crossing the area Wednesday night. Moderate
shear and decent elevated instability could allow some of the storms
to become strong to severe. The severe threat could continue into
Thursday as another round of convection moves through. Moderate
shear is likely, with moderate instability possible, especially if
the cap can erode and LFCs become low enough. Any convection that
does develop should quickly move east early Thursday evening.

The GFS continues to be more aggressive with the next short wave
dropping into the area Friday, and the resulting cyclogenesis. It is
the wettest guidance, but there is some response from the other
guidance. Have gone with the model blend for PoP which favors the
mountains and CLT Metro. This is still in the chance range across
the entire area. QPF that does fall will be light. Temps will be
well above normal Thursday, dropping to around normal Friday.

&&

.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
As of 155 PM EDT Tuesday: Not much change in the forecast this
period with short waves rotating through a low amplitude long wave
trough over the eastern CONUS. Weak surface features move over or
near the area in association with the short waves through Monday.
There may be enough moisture for isolated to low end scattered
showers across the mountains, but any QPF will be light with a dry
forecast elsewhere. Model differences develop Tuesday with a
stronger wave rotating through the upper trough producing
cyclogenesis along the Gulf Coast with the resulting low moving
south of the area. How far south is the question with a drier,
farther south track and wetter, farther north track. Have gone with
the guidance blend which has low end chance PoP developing. Temps
below normal Saturday slowly rise to slightly above normal by
Tuesday.

&&

.AVIATION /06Z WEDNESDAY THROUGH SUNDAY/...
At KCLT and elsewhere: Expecting a relatively quiet overnight with
residual convective debris cloudiness and a light mostly SW wind.
There is the concern that fog could develop across the mtns and near
KHKY, and it was indicated in the guidance. Low level moisture
remains plentiful, so we include a fog restriction in the predawn
hours for KAVL and KHKY, even though a blanket of high level clouds
will remain. Today looks like it could be an active day
convectively...eventually. Models show some shower development early
in the day over the mtns, so a TEMPO was included at KAVL to handle
the rain chance and the possible lower fog/ceiling restrictions.
Once rid of that, all terminals go VFR prevailing for the rest of
the period. Wind will come up from the SW with some possible gusts.
Then, we wait. There is much uncertainty as to the coverage and
timing of any afternoon convection, so a broad-brushed PROB30 will
be employed for thunderstorms in the last six hours of most
forecasts. We will evaluate the morning guidance and fine-tune the
timing of the best thunderstorm chances the next set of TAFs.

Outlook: A cold front will approach out of the west on Thursday
before tracking over the terminals Thursday night into early Friday
morning. This will lead to better convective chances, as well as
restrictions. A system lifting out of the south my increase shower
and thunderstorm chances again on Friday, but confidence on this
remains low. Drier conditions can be expected this weekend.

&&

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

&&

$$

SYNOPSIS...AR
NEAR TERM...AR/TW
SHORT TERM...RWH
LONG TERM...RWH
AVIATION...TW