967
FXUS62 KGSP 070741
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
341 AM EDT Tue May 7 2024

.SYNOPSIS...
A summerlike weather pattern lingers through mid-week with mainly
diurnal 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 TONIGHT/...
As of 330 AM EDT Tuesday: A weak shortwave trough will remain over
the western Carolinas through daybreak, keeping convection around
for portions of the forecast area. Latest radar mosaic loops show
scattered showers, with some embedded thunder at times, across the NC
Piedmont and Foothills and across the eastern SC Upstate. Some
isolated activity lingers this morning along the NC/TN border and
the SW NC mtns as well. Have PoPs gradually decreasing through
daybreak as the trough gradually pushes east. Lows this morning will
end up around 10 degrees above climo thanks to cloud cover and
precip.

upper riding will build across the Southeast today leading to much
warmer temperatures as well as a lower coverage of diurnal
convection. Temperatures this afternoon will climb into the lower
80s in the mtn valleys and the mid to upper 80s east of the mtns.
This will yield highs around 8-10 degrees above climo. CAMs agree
that isolated storms will develop mid to late afternoon across the
NC mtns and Foothills before pushing east into the NC Piedmont late
this afternoon into early this evening. With the rest of the
forecast area expected to remain dry, went with chance PoPs across
western NC for today. The SPC Day 1 Severe Wx Outlook shows a
Marginal Risk for isolated severe storms across western NC today.
This make sense as 25-35 kts of 0-6 km bulk shear and up to 2,500
J/kg of SBCAPE in place this afternoon will allow for severe storm
development. Any lingering convection this evening should quickly
wane around sunset with the loss of daytime heating.

Another round of overnight convection may develop as a cold front
slowly approaches out of the west. However, with CAMs not in
agreement on shower and thunderstorm activity, confidence will
remain very low regarding tonight`s PoPs. Lows tonight should end up
around 13-15 degrees above climo, especially if cloud cover and
convection manage to develop.

&&

.SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
As of 305 am EDT Tuesday: Convection may be ongoing at the start of
the short term...and in fact the highest PoPs for Wed will be in the
morning. An elevated mixed layer is forecast to advect into the area
from the southwest  during the afternoon/evening. This will act to
impressively steepen mid-level lapse rates...to the tune of 7.5 C/
km. However, it will also act to cap the atmosphere, as forecast
soundings depict a strengthening inversion between 5 and 7 kft. As a
result, most model guidance...in particular the convection-allowing
models...have very little in the way of a convective response across
our area Wed PM. Having said that, the afternoon air mass will
actually become quite volatile due to the cooling aloft and strong
insolation/hot boundary layer (max temps of around 90 across much of
the Piedmont), with sbCAPE of around 3000 J/kg expected during
mid/late afternoon. If a couple of cells are able to initiate in
this environment...perhaps before capping becomes too strong during
mid-afternoon...they are likely to become strong-to-severe, with
deep layer shear of ~35 kts suggesting good potential for
supercellular structures.

If anything, forecast soundings indicate stronger capping Wed night
into early Thu. However, convection originating from the very
unstable and strongly sheared pre-frontal environment to our west
could certainly make a run toward our western areas at any point
during this time frame. Convective chances then ramp up across our
area during the daylight hours Thursday as frontal zone pushes in
from the west...most likely during peak heating. The forecast is
somewhat muddled due to the potential for early day convection
cooling/stabilizing the atmosphere...at the very least, more in the
way of cloud cover is expected on Thu that will act to somewhat
inhibit heating/destabilization. However, while the cap is forecast
to be eliminated by the daylight hours Thu, a remnant elevated mixed
layer regime is still expected to result in rather steep mid-level
lapse rates, so it won`t take a great deal of heating to yield at
least moderate levels of sbCAPE during the afternoon. Shear
parameters will only continue to improve, with 0-6km bulk shear of
40-45 kts expected. Westerly/quasi-boundary-normal shear vectors
once again suggest the potential for supercell structures and
perhaps smaller linear segments...with low level shear parameters
being adequate for perhaps a couple of tornadoes in addition to
large hail and damaging downbursts. Convection is expected to come
to quick end Thu evening as a drier air mass advects into the area
in the wake of the front.

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
As of 330 am EDT Tuesday: The 00Z GFS is an outlier in its depiction
of a potent short wave trough digging into the TN Valley and
southern Appalachians on Friday (other guidance is considerably
farther north). As a result of this, the GFS solution would have a
surface wave develop across the baroclinic zone across the Deep
South, with additional rounds of convection making a run for our
forecast area during the day Fri. Again, this is an outlier, but
there`s enough a signal in deterministic and ensemble guidance to
include chance PoPs during the day. The remainder of the extended
should be cooler and much drier as a long wave trough becomes
established across the East. Surface dewpoints in the 40s...possibly
in the 30s across the mountains will result in wide diurnal
temperature ranges...with below normal min temps and near-to-
slightly-above normal highs through the period.

&&

.AVIATION /08Z TUESDAY THROUGH SATURDAY/...
At KCLT and elsewhere: Pesky convection continues this morning
across the SC Upstate, NC Piedmont, and the northern and central NC
mountains with some sites seeing MVFR restrictions. Thunder
potential has really died down within last few hours. Thus, only
isolated lightning is expected with activity this morning. SHRA is
currently impacting KCLT, KGMU, and KGSP as of 06Z. Went with a
TEMPO for SHRA at KCLT from 06Z-10Z and VCSH at KGSP and KGMU from
06Z-08Z. KAVL will see another round of SHRA impact the terminal
here shortly, so have a TEMPO for SHRA from 06Z-09Z. KHKY will see
another round of -RA from 08Z-11Z, with VCSH in place prior to 08Z.
KAND is expected to remain dry the rest of the TAF period. Cigs are
expected to lower through daybreak, becoming IFR to MVFR. Vsbys are
expected to drop through daybreak as well thanks to the rainfall
from yesterday and this morning. Most locations should see MVFR
vsbys, although KAVL may see vsbys drop to LIFR around daybreak.
Vsbys and cigs should gradually improve after sunrise, becoming VFR
by 13-14Z. VFR conditions will linger through the rest of the 06Z
TAF period outside of isolated thunderstorms tracking across western
NC this afternoon into early this evening. Went with PROB30s at all
of the NC TAF sites to account for TSRA. Afternoon cumulus will
develop thanks to daytime heating and low-end wind gusts will be
possible at KAVL and the SC Upstate terminals this afternoon. Wind
direction should generally be SW east of the mtns and W/WSW across
the mtns through the TAF period.

Outlook: Diurnal convection returns again on Wednesday. There is
potential for restrictions associated with widespread fog and/or low
stratus each morning for any terminals that receive rainfall the
day/night prior. 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...AR
NEAR TERM...AR
SHORT TERM...JDL
LONG TERM...JDL
AVIATION...AR