-- Discussion containing changed information from previous version are highlighted. --
695
FXUS62 KGSP 210559
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
159 AM EDT Sat Sep 21 2024

.SYNOPSIS...
High pressure will linger across the area today, though we could see
some widely scattered showers and storms through this evening.  High
pressure will remain through early next week, with hot temperatures
expected over the weekend, before a wetter pattern arrives after
Tuesday.

&&

.NEAR TERM /THROUGH TODAY/...
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As of 145 am: Heights will gradually rise through the period as a
ridge extending from an upper anticyclone over Texas nudges into the
region. Weak surface high pressure remains over the area through the
period as well. Mostly clear skies early this morning will combine
with light winds and ample low level moisture to yield another round
of widespread mountain valley fog and low stratus, while fog is also
expected to continue expanding outside the mtns, especially in some
of the major river valleys. With the boundary layer being slightly
drier than at this time yesterday, expect any dense fog to remain
patchy this morning. Lows will be up to 5 degrees above normal.

Instability looks to be lower later today with warming mid levels.
Still there my be enough to combine with differential heating for
isolated convection along and near the Blue Ridge during the
afternoon. Highs will be around 5 degrees above normal.
-- End Changed Discussion --

&&

.SHORT TERM /TONIGHT THROUGH MONDAY/...
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As of 136 PM EDT Friday: Fairly good agreement on the forecast for
the latter half of the weekend and into Monday.  Subtropical ridging
will build over the southern US and Gulf of Mexico through the
period, sharpening on Monday in response to increased troughiness
over the Continental Divide and points west.  This`ll maintain
mostly dry and suppressed conditions over the area on Sunday, before
a broad and ill-defined baroclinic zone arrives in the Ohio Valley
Monday.  Ripples of shortwave energy aloft will ride up and over the
ridge, lending a little synoptic forcing to an otherwise murky
setup. So, increasing PoPs are warranted through the end of the
period Monday evening. Temperatures will likely hit the upper
80s to lower 90s on Sunday, with the highest temperatures to be
found across the Savannah River Valley; on Monday, they`ll fall
back into the upper 80s in most locations in response to the
weakening ridge and enhanced cloud cover.
-- End Changed Discussion --

&&

.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
As of 148 PM EDT Friday: Lower-than-typical confidence as we look
out into the medium range.  Another round of more focused shortwave
energy will arrive on Tuesday, further suppressing the ridge over
the eastern CONUS; it`s unclear, though, how strong this effect will
be.  The latest operational GFS depicts the ridge remaining in
place, if perhaps migrating even farther east and exposing the
Carolinas to better deep-layer SW flow and accompanying moisture
flux.  The most recent two runs of the ECMWF depict a complete
dissolution of the ridge, with a massive upper low developing over
the Mid-Atlantic by Wednesday.  The 12z GDPS, comparatively, depicts
an open trough and associated surface front arriving on Wednesday
and Thursday and scouring out the remnants of the ridge.  The
broader ensemble envelope of solutions clearly favors the more
progressive solutions depicted by the GFS and GDPS, but there`s
around 25% support for a more EC-like upper low solution as well.
That is to say, predictability is fairly low past Tuesday or so, but
most solutions will result in some sort of more active/rainy setup
through the medium range...and the more GFS-like solutions would
even introduce some afternoon instability each day, resulting in at
least some isolated thunder chances!

&&

.AVIATION /06Z SATURDAY THROUGH WEDNESDAY/...
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At KCLT and elsewhere: Ample low level moisture lingers across the
Terminal Forecast Area early this morning, creating the potential
for another round of fog/low stratus at the TAF sites later this
morning. Having said that, the near-surface layer is a little drier
than at this time yesterday, so restrictions have been slower to
develop. Nevertheless, expect at least tempo IFR/LIFR conditions to
develop at KHKY/KAVL by daybreak. As was the case yesterday,
confidence in restrictions is not especially high at KCLT, but
there`s enough evidence to forecast a couple of hours of IFR cigs
(w/ MVFR visby) there toward sunrise. Otherwise, restrictions should
be limited to perhaps brief tempo MVFR conditions at the upstate SC
terminals. Winds will generally be calm or light/vrbl this morning,
becoming light southerly during the daylight hours. Isolated to
perhaps widely scattered diurnal convection is expected this
afternoon and evening, but coverage is again expected to be too
sparse to warrant a TAF mention at any site.

Outlook: No appreciable return of moisture or precip chances
expected until early to middle of next week. Daybreak restrictions
could recur each morning especially in mountain valleys.
-- End Changed Discussion --

&&

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

&&

$$

SYNOPSIS...MPR
NEAR TERM...JDL/RWH/Wimberley
SHORT TERM...MPR
LONG TERM...MPR
AVIATION...JDL