954
FXUS62 KGSP 221844
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
244 PM EDT Wed May 22 2024

.SYNOPSIS...
Temperatures will remain several degrees above normal each day
through Tuesday of next week as humid subtropical air remains
over the Southeast. Chances for showers and thunderstorms increase
Thursday and will remain higher than normal for this time of year
into next week as well.

&&

.NEAR TERM /THROUGH THURSDAY/...
As of 211 PM EDT Wednesday: All quiet across the western Carolinas
this afternoon as potent ridging extends from the Mississippi
Delta region up into the Carolinas.  Observed profiles from our
scattering of ACARS sites depict a weak subsidence inversion and,
in general, poor lapse rates through the depth of the troposphere;
so, no convection has managed to fire off despite decent ~1000
J/kg sbCAPE.  Rather, a rapidly-thickening fair-wx cumulus field
has developed, but has remained capped.

This should continue as the ridge remains more or less stationary
over the Southeast this evening.  Most of the hi-res guidance
fails to produce any convective initiation, even over the
mountains; only notable exceptions are the FV3 and NSSL-WRF,
both of which tend to run hot under these circumstances (nebulous
forcing, moderate capping).  So, expect increasing cloud cover,
and while a weak shower over the mountains can`t be ruled out,
it looks increasingly like a dry day for all.  Winds will get
increasingly steady out of the SW as we become locked into a
weak warm advective/moisture flux regime.  Temperatures will soar
into the mid- or even upper-80s outside the mountains.  Tonight,
the ridge will retreat toward the coast, and cirrus will thicken
across the western Carolinas.  Ripples of weak synoptic forcing
will arrive during the predawn hours, but will encounter air too
dry to support any precipitation, even over the mountains.  Rather,
thickening cloud cover will only help to inhibit fog formation in
the mountain valleys through daybreak, while keeping lows in the
mid-60s, a category warmer than this morning.

Rainfall won`t arrive until after 12Z, at which point upper heights
will begin falling more quickly and a cold front will sag into the
upper Tennessee Valley / Cumberland Plateau.  Afternoon profiles
tomorrow look much more favorable for convection; the influx of
cold air aloft will steepen lapse rates and today`s subsidence
inversion will vanish, permitting the development of some 1000-1500
J/kg sbCAPE, perhaps more over the I-77 corridor.  Although the
environment will be only weakly to moderately sheared (<30kts deep
layer, anyway, and with minimal low-level shear)...HRRR and NAM
soundings do depict 900-1200 J/kg sbCAPE, especially across the
northern Upstate and I-77 corridor.  So...downburst winds are a
real possibility from any developing updrafts.  SPC`s Marginal
Risk for Severe Weather, highlighting both wind and hail, looks
reasonable enough.

&&

.SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY/...
As of 215 PM Wed: A series of short waves will cross the area with
some sort of weak surface feature associated with the waves. This
will lead to mainly diurnal convection each day, with some lingering
showers possible during the overnight periods. Moderate instability
and bulk shear around 40 kts is possible on Friday, along with
decent sfc delta Theta-e values. A few severe storms will be
possible with some organization. With the good forcing in place,
expect widespread to numerous convective coverage of the mountains
and foothills and high end scattered coverage elsewhere. Temps will
be around 5 degrees above normal.

Coverage will not be as widespread on Saturday, but high end
moderate instability, along with 20 kts of shear and continued high
levels of sfc delta Theta-e values, along with increasing dCAPE may
lead to an uptick in severe thunderstorm chances. These would be
more of the pulse severe, damaging wind variety. Temps will be
around 10 degrees above normal.

&&

.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
As of 230 PM Wed: Unsettled weather expected into early next week as
the series of short waves continue to march across the area. Again,
there looks to be weak surface features until Monday when a more
organized cold front crosses the area. Expect precip chances to
steadily increase Sunday and Monday, although the convection should
be mainly diurnal. Some severe storms will be possible again
especially if the moderate instability and shear and dCAPE overlap.
Temps will be 5 to 10 degrees above normal.

Some lingering showers possible Tuesday even as the front moves
east, but thunder chances diminish. Temps will be up to 5 degrees
above normal. Dry high pressure expected on Wednesday with temps
near to slightly above normal.

&&

.AVIATION /19Z WEDNESDAY THROUGH MONDAY/...
At KCLT and elsewhere: Another quiet TAF period for most terminals.
An extensive cu field has begun to develop across most of the
terminal forecast area, and should increase in coverage in the
coming hours.  However, it should largely remain capped due to
robust upper ridging; the hi-res guidance depicts virtually no
convective activity this afternoon, even across the mountains, as
conditions will simply be too unfavorable for deep moist convection.
Any showers that do manage to develop will be weak and short lived,
and confined to the NC mountains.  At KAVL, confidence was too
low for any mention.  Tonight, cirrus will thicken across the
area ahead of an advancing wave.  Isolated shower activity may
make it into the mountains after midnight, but will largely
fizzle out upon arrival.  The increased cloud cover, though,
should somewhat hamper fog/low stratus in the mountain valleys,
such that KAVL is forecast to remain VFR through the overnight.
For KAVL, the first ripples of SHRA/TSRA will arrive during the
final few hours of the TAF period, late Thursday morning, and have
been handled with a PROB30.  Similarly, for KCLT, whose TAF period
extends into Thursday evening, a PROB30 was added for the arrival
of TS in the I-77 corridor at that time.

Outlook: Numerous showers and thunderstorms, along with associated
flight restrictions, will continue Thursday night and Friday as a
cold front crosses the region. A more active pattern may persist
through early next week.

&&

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

&&

$$

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