957
FXUS62 KGSP 080027
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
827 PM EDT Tue May 7 2024

.SYNOPSIS...
A summerlike weather pattern lingers through mid-week with mainly
afternoon and evening showers and thunderstorms expected.
Temperatures will trend well above normal through Thursday. Showers
and thunderstorms will become more numerous ahead of a strong cold
front on Thursday. Activity may linger through early Friday as the
cold front pushes east of the western Carolinas. Drier conditions
and below normal temperatures return for the weekend as high
pressure builds in from the west.

&&

.NEAR TERM /THROUGH WEDNESDAY/...
As of 813 PM EDT Tuesday: A persistent right-moving storm
with supercellular characteristics finally got undercut and
was unable to recycle, thus it died quickly east of I-77 near
Statesville. Although we still have upwards of 2000-3000 J/kg of
sfc-based CAPE to work with over the western Piedmont, we are
seeing the development of a weak capping inversion now that we
are at sunset. With no more storms in our area east of the mtns,
it would appear that our storm threat has ended. Not going to
rule out another shower or two. Meanwhile...a few smaller showers
and thunderstorms will run into the nrn mountains and die out by
01Z-02Z. After that, the latest runs of the HRRR suggest it will
be quiet overnight. Temp trends look good outside places affected
by the recent storms.

Otherwise...an active period of weather will continue through
Wednesday with multiple rounds of thunderstorms, some of which
could be severe, expected. As of this writing, water vapor imagery
depicts a large negatively tilted trough draped across the Great
Plains into the Midwest with a closed upper low spinning over the
Northern Plains. Farther east, upper ridging over the Appalachians
will breakdown and shift offshore with a highly perturbed southwest
flow regime setting up shop from the Lower Mississippi Valley into
the Southern Appalachians. This will send multiple rounds of storms
into the area through the near term forecast period.

By the predawn hours, a batch of showers and perhaps a couple
thunderstorms will be possible across the mountains and portions
of the Upstate. Thereafter, a residual elevated mixed layer will
advect into the area and help 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 would appear warranted.

&&

.SHORT TERM /WEDNESDAY NIGHT 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 /01Z WEDNESDAY THROUGH SUNDAY/...
At KCLT and elsewhere: Thunderstorm to the north of KCLT is not
expected to affect the terminal, but will move through the northern
approach well north of the terminal. Once that cell is either
gone to the east or dies out, we expect it to be 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. Tomorrow 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 evening guidance and fine-tune
the timing of the best thunderstorm chances in later TAFs.

Outlook: A cold front will approach out of the west on Thursday
before tracking over the terminals Thursday night into Friday
morning. This will lead to better convective chances, as well as
restrictions, towards the end of the workweek.

&&

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

&&

$$

SYNOPSIS...DEO
NEAR TERM...TW
SHORT TERM...RWH
LONG TERM...RWH
AVIATION...TW