597
FXUS62 KGSP 121036
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
636 AM EDT Sun May 12 2024

.SYNOPSIS...
One more day of dry weather is expected today, before rain returns
Monday afternoon.  Rain and thunder are expected on Tuesday and
Wednesday, followed by a brief stint of dry conditions on Thursday.
Active conditions will resume for the weekend.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 635 AM: Patchy mountain valley fog dissipates quickly this
morning. Then an upper ridge axis builds in through the period as a
trough moves east of the area. At the surface, a lee trough sets up
over the area today with the center of high pressure building in
tonight. After some patchy mountain valley fog, mostly sunny skies
expected with slowly increasing cirrus. Increasing thickness values
and west to northwest flow will help highs rise to around normal.
With a dry air mass remaining in place, RH values will approach 25
percent outside of the mountains. Winds will be relatively light
outside of the mountains with low end gusts possible. Gusty winds
expected across the mountains, but RH values remain above 25
percent. Moisture values should remain above critical levels keeping
Fire Weather concerns low.

Cirrus becomes thick and widespread tonight as upper level moisture
move in ahead of the next weather system. Despite light winds and a
dry air mass, the cirrus will help keep temps slightly elevated.
Lows end up near to slightly below normal.

&&

.SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
As of 246 AM EDT Sunday: No major changes to the short term
forecast.  It still appears that Monday will be a transitional
day, as profiles saturate from the top down.  A shallow dry layer
near the surface will hold precipitation at bay for a while,
but overall guidance has sped up with bringing rainfall in Monday
afternoon/evening.  Categorical PoPs are warranted Monday night
as isentropic ascent ramps up and a wedge-like pattern sets up.
Lows will fall into the lower 60s outside the mountains.

On Tuesday, deeper synoptic forcing will arrive as a cutoff low
develops over the Ozarks and a weak upper jetlet sharpens over the
Mississippi Valley...supportive of deep forcing over the Carolinas.
Operational guidance is increasingly supportive of the wedge front,
while initially south of the forecast area, gradually eroding
through the afternoon in response to intense low-level WAA; this
will allow some surface instability on the order of 500-1000 J/kg to
develop over most of the forecast area by mid-afternoon.  As a 500mb
speed max rounds the base of the advancing upper low late Tuesday,
deep layer shear values will surge to 40kts or more by evening
and into the overnight.  So, Tuesday, especially Tuesday night,
is inreasingly looking like our next window for severe weather.
Highs on Tuesday will be limited by the weak CAD configuration and
widespread cloud cover, and will only climb into the lower 70s.
Tuesday night, lows will again fall into the lower 60s.

&&

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
As of 304 AM EDT Sunday: By Wednesday, the western Carolinas will
be ensconced in warm sector air ahead of an advancing surface low,
which should carry a cold front across the area by late in the day.
Operational guidance once again brings 1000+ J/kg into the Piedmont
and Upstate during the afternoon hours, but shear looks to be
notably weaker with diminishing 500mb flow...so severe risk may
be muted compared to Tuesday.

Ridging is still expected on Thursday, which should keep
precipitation at bay.  By Friday, another upper low drifting out
of the central Great Plains will incite a lobe of upper forcing
from the southern stream, and active weather will resume Friday
and Saturday.  At least diurnal convection is therefore likely
Friday onward.

&&

.AVIATION /12Z SUNDAY THROUGH THURSDAY/...
At KCLT and elsewhere: Expect cirrus to increase in coverage and
thicken through the day into the evening and continue overnight. W
to NW wind through the day for the NC sites, with low end gusts at
KAVL. Winds start WNW for the Upstate sites then turn WSW during the
afternoon. Low end gusts can`t be ruled out. Winds diminish and turn
NE during the evening.

Outlook: Deep moisture returns on Monday with active weather and
associated restrictions Tuesday and Wednesday. Brief drying expected
Thursday.

&&

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

&&

$$

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