176
FXUS62 KGSP 071849
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
249 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 213 PM EDT Tuesday: 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. Action starts this afternoon with several
convective towers noted on visible satellite imagery and radar
across the mountains and foothills. This activity is expected to
further deepen over the next several hours within a moderately
unstable and weakly sheared environment. A dry sub-cloud layer
supports 700-1000 J/kg of DCAPE, thus any deeper storms could result
in locally damaging winds and isolated large hail. The greatest
threat for isolated to scattered severe storms will be across the
mountains and along the I-40 corridor. Heading into tonight, any
afternoon storms should dissipate by this evening with generally
quiet conditions persisting overnight.

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 /19Z TUESDAY THROUGH SUNDAY/...
At KCLT and elsewhere: Afternoon cumulus field will continue to
build across the area over the next several hours. A few isolated to
scattered showers and thunderstorms will be possible across the
mountains and foothills (KAVL/KHKY) with lesser confidence towards
KCLT. Mainly quiet conditions are expected overnight, but a batch of
showers could bring restrictions to KAVL/KGSP/KGMU during the
predawn hours. Thereafter, another afternoon cumulus field is
expected along with increasing coverage of showers and thunderstorms
by the afternoon. Confidence as to when/where thunderstorms may be
tomorrow afternoon is too low to warrant mention in the TAFs just
yet. Otherwise, generally light winds are expected out of the
west/southwest.

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