298
FXUS62 KGSP 091912
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
212 PM EST Sat Nov 9 2024

.SYNOPSIS...
Dry high pressure will persist today before a cold front brings rain
and cooler temperatures back to the area Sunday afternoon into
Monday.  Dry high pressure will return Tuesday and Wednesday, before
another cold front arrives toward the end of next week.

&&

.NEAR TERM /THROUGH SUNDAY/...
As of 204 PM Saturday: Fairly quiet across the region this
afternoon, and that is expected to continue as sfc high pressure
ridges down from the northeast in what is essentially a dry cold
air damming wedge at this point. The lingering stratocu seen
on satellite imagery over northeast GA and the Upstate belies
the developing southerly flow across the region. Meanwhile, some
thin cirrus was streaming in from the WNW. Should be dry into the
evening. Temps were in good shape, so no changes are necessary at
this time.

Over the next 12 hours or so, a transition will take place
toward a more productive hybrid cold air damming wedge as the
weakening parent high gets pushed off the Mid-Atlantic coast
by the progressive nrn stream ridge. The southerly flow will
gradually increase tonight with isentropic lift commencing in the
early morning hours, altho the moisture takes a few more hours
to arrive. But, arrive it should, by daybreak or so with clouds
and light precip developing first in the southerly upslope areas
of the Blue Ridge Escarpment, and then expanding outward from
there during the morning as the isentropic lift improves. The
CAMs indicate more shower activity than previous model runs,
so the precip chances were bumped up and expanded mainly east
of the mountains into the afternoon. Still in the chance range,
but trending upward, and suspect that more people will get some
light rain than not. Meanwhile, the approach of a cold front from
the west will increase the rain chances over the western side of
the mtns in the afternoon. This fcst trend also supports more
cloudiness, which is more likely to lock in the hybrid wedge,
and keep temps below normal. Thus, the high temp was also nudged
downward a bit for Sunday afternoon.

&&

.SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY/...
As of 1232 PM EDT Saturday: CAD should begin to erode on Monday.
Model soundings depict a shallow wedge still in place early Monday
morning, but by Monday afternoon/evening, deep mixing should start
to erode the wedge from the bottom up.  It`ll be a one-two punch,
too, as potent, if short-lived, low-level CAA arrives with a cold
front digging across the Tennessee Valley. This should effectively
end CAD and allow high pressure to begin building in from the north
on Tuesday.  This will lead to a period of drying, though the center
of the high will be migrated eastward quickly enough that by Tuesday
evening, it`ll already be pushing out of the Ohio Valley and into
the Adirondacks.

So, this will play out as increasing shower activity through Monday
morning , leading up to the arrival of the actual frontal
circulation Monday afternoon.  Rain chances will then diminish
Monday night as the boundary pushes eastward.  Given the depth of
mixing, it`s still not out of the question that we could see a stray
surface-based thunderstorm...but even the most aggressive models
depict a weak residual cap, severely limiting the strength of any
such cell.  Drying is then expected through the remainder of the
period, with mostly clear skies expected Tuesday.  The front will do
little to moderate temperatures, which will be in the low- to mid-
70s both afternoons.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
As of 116 PM EDT Saturday: As surface high pressure continues to
work its way east under a progressive upper pattern, we`ll gradually
revert to a northeast-flow CAD-like pattern on Tuesday and
Wednesday.  Profiles look to remain dry enough, however, and
isentropic ascent weak enough, to preclude the usual dreary weather
associated with established cold-air damming.  Instead, expect
enough afternoon mixing for scattered cloud cover only. Temperatures
will climb into the 70s on Tuesday, but by Wednesday, the intrusion
of cooler air from the northeast will result in afternoon highs in
the mid 60s.

Wednesday night or early Thursday, a cold front is still expected to
make tracks across the area.  This will result in a brief period of
showers from Wednesday night through the first half of the day
Thursday.  Synoptic forcing will be modest at best, and with a weak
frontal circulation given how far removed the parent low will be.
Behind the front, robust high pressure will build in from the
central U.S.  This will somewhat decrease temperatures, but the
effect will be more noticeable at night - with Thursday and Friday
night`s lows falling into the 40s or even upper 30s in some spots -
than during the day, when solar heating and weak downslope flow
could offset any CAA-induced cooling.

&&

.AVIATION /19Z SATURDAY THROUGH THURSDAY/...
At KCLT and elsewhere: Weak cold air damming will continue
this afternoon and evening, but the air mass will remain
dry, so other than some high-based stratocu, not much will be
happening. Conditions should remain VFR, with a NE wind at the
sfc, well into the evening. Toward daybreak, that will change
as moisture arrives from the S and SE. Low ceilings and light
precip will develop first along/near the Blue Ridge Escarpment
after midnight, eventually expanding to encompass the Upstate
terminals and KAVL. Restrictions will develop in those locations
after daybreak, beginning mainly as MVFR ceilings. As the moist
upglide flow from the south persists, the precip and clouds will
expand across the region, bringing the entire forecast area under
MVFR, and eventually IFR by the end of the period at KCLT.

Outlook: A wedge regime will persist until a cold front passes
Monday night or Tuesday. Periodic restrictions and precip are
likely Sunday night and Monday. Dry and mostly VFR weather expected
Tue-Wed.

&&

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

&&

$$

SYNOPSIS...MPR
NEAR TERM...PM
SHORT TERM...MPR
LONG TERM...MPR
AVIATION...PM