-- Discussion containing changed information from previous version are highlighted. --
098
FXUS62 KGSP 182210
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
610 PM EDT Wed Sep 18 2024

.SYNOPSIS...
The remnants of the coastal low will gradually dissipate or move
off the Mid Atlantic coast by Friday.  Meanwhile, high pressure
begins to build into the region from the north and west giving our
region a dry weekend. Temperatures will be near normal.

&&

.NEAR TERM /THROUGH THURSDAY/...
-- Changed Discussion --
As of 6 pm...The swirl in the low clouds seen in the vis satellite
imagery belies the location of a cutoff low over Upstate SC near
Union or thereabouts. Enough breaks in the clouds have allowed for
500-1000 J/kg of sfc-based CAPE per the SPC mesoanalysis, which
is plenty to work with to produce scattered showers in two parts
of the fcst area...one over the west and one over the east. Won`t
rule out a stray thunderstorm in the area east of I-77 where the
CAPE is just a bit deeper and a few lightning strikes have been
observed. Some of the showers could have high rainfall rates and
were moving fairly slow, but the small size will cut down on the
duration enough that no problems are expected.

Otherwise...the upper low will lose any connection with the sfc
pattern overnight and slowly shift east of the forecast area thru
the day on Thu. Still expect a good amount of low level wrap around
moisture in the wake, which will be able to develop isolated to
scattered pulse showers and possibly a few thunderstorms with
increasing instability during the afternoon. Overall, an improving
pattern as far as lessening cloud cover and temps will respond to
arnd 80 F outside the mtns, a few degrees warmer toward northeast
GA, and u70s mtn valleys. A dense fog threat is possible arnd
daybreak across the NC mtn valleys as better radiational cooling
conditions interact with a rather moist sfc layer. Lows will
generally be held a couple degrees abv normal.
-- End Changed Discussion --

&&

.SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY/...
As of 157 PM Tuesday: As we head into Friday and Saturday, upper
ridging will slowly drift east from the Southern Plains into the
Lower Mississippi Valley. Heights will rise through the period
across the Southern Appalachians with increasing subsidence. At the
surface, high pressure will extend down the spine of the
Appalachians form a parent high centered near the Hudson Bay.
Guidance still indicates the presence of a backdoor cold front
oozing into portions of the Carolinas from Virginia. A noticeable
change, however, is that guidance is less aggressive with clearing
the boundary through the area, thus keeping dewpoints in the low to
mid 60s. The airmass will be drier, relatively speaking compared to
the tropical origins of the current airmass, but PWATs may not fall
as appreciably. While a stray shower or two cannot be ruled out,
increasing subsidence from the building upper ridge will generally
preclude mentionable PoPs outside of the Blue Ridge escarpment on
Friday. Temperatures will continue to warm through the period with
highs back into the low to mid 80s.

&&

.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
As of 206 PM EDT Wednesday: A warming trend will continue Sunday
into early next week as the axis of the upper ridge becomes centered
over the Appalachians. Warming H85 temperatures and deep/efficient
mixing of the boundary layer will promote high temperatures in the
mid to upper 80s on Sunday, which will likely be the hottest day of
the period. A few locations may even reach the 90 degree mark across
the Upper Savannah Valley. The forecast will remain dry, however, as
a stout subsidence inversion present on forecast soundings deters
any convection. By Monday into Tuesday, a shortwave trough swinging
across the Midwest will drag a cold front towards the area. Timing
of the trough and attendant front remains elusive at this time
range, but a gradual uptick in PoPs will be warranted across the
mountains as the boundary nears.

&&

.AVIATION /22Z WEDNESDAY THROUGH MONDAY/...
At KCLT and elsewhere: A tricky TAF set in store as an upper low
continues to produce low clouds and VSBY issues. Expect some
improvement to VFR this afternoon, esp at KCLT. The wrn sites could
remain socked in (MVFR/IFR CIGs) for a while with deeper moisture
continuing to train and lift over the area. All sites will likely
drop to IFR, mainly due to CIGs, overnight with MVFR VSBY probable
as well. At KAVL, a good signal for a drying column as the low
shifts east thereby setting up a possible dense fog threat arnd
daybreak. Expect improving conds late period all sites to either
MVFR or VFR. Winds remain light thru the period favoring a ne/ly
direction.

Outlook: On Friday, sfc high pressure builds into the area from the
north allowing drier weather and VFR conditions to return into this
weekend.

&&

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

&&

$$

SYNOPSIS...DEO
NEAR TERM...PM/SBK
SHORT TERM...TW
LONG TERM...TW
AVIATION...SBK