626
FXUS62 KGSP 251844
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
244 PM EDT Sat May 25 2024

.SYNOPSIS...
Temperatures will remain above normal through the holiday weekend
with a chance of afternoon and evening thunderstorms. A cold front
brings another chance of showers and thunderstorms on Monday. Cooler
and drier conditions move in behind the front and remain through the
end of the week.

&&

.NEAR TERM /THROUGH SUNDAY/...
As of 225 PM EDT Saturday: Subtle vort energy residing within
the mean flow of flat upper ridging over the area is providing
enough upper forcing to help kick off ongoing convection across
portions of the CFWA. Morning convection likely helped suppress
the environment somewhat, but not fully. Starting to see signs
of clearing in areas that have been let untapped, mainly in the
NC foothills/Piedmont. Could see a few storms being initiated via
differential heating boundary due to a near 10 degree temperature
difference between locations that received morning shower/storms
and those that were able to clear. CAMs are not that excited about
the overall coverage of thunderstorms this afternoon/evening, but
the storms that do develop have the potential to become strong to
severe. 1500-2500 J/kg of sbCAPE, weak deep layer shear, and PWAT
values ~1.50" or higher will support wet microbursts as the main
threat, but large hail (1.00") can`t be ruled out. Model guidance
indicate that most of the activity will be diurnally driven as
most locations dry out by midnight tonight and will remain that way
through the overnight period. Had to lower max temps for today due
to more extensive cloud debris, but values will still top out a few
degrees above normal. Clouds will gradually scour out overnight, but
mid to high clouds may not fully go away. Overnight lows will be ~5
degrees above normal as dewpoints remain elevated and cloud cover
lingers. Patchy dense fog can`t be ruled out either, especially
in locations that receives rainfall this afternoon and evening.

Warm and humid airmass continues on Sunday as convection across
the Plains and Midwest gradually travel east. This will likely
generate an MCV that will slip into the OH Valley, which will
push south and east towards the CFWA via CAMs. Deep layer shear
won`t be great, but an increasing LLJ (20-30 kts) with 40-50 kts
of mid-level flow will begin to filter in across the region late
Sunday afternoon just as convection gets into the region. A westerly
component to the mid-level winds will allow for some type of dry
air entrainment. This will help to create a damaging wind threat,
especially if a cold pool can become generated and the convection
ingest some form of upscale growth. Best locations will be the
NC zones and the northern Upstate, but the timing may slip into
the beginning portions of the short-term, meaning that the onset
isn`t expected until after 18Z in the NC mountains before pulling
east across the rest of the CFWA. Afternoon highs should be able
to reach the upper 80s to near 90 as morning convection is not
expected, so there should be less cloud debris until peak heating
arrives and convection pops off.

&&

.SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY/...
As of 145 PM EDT Saturday: Weak ridging with diffluent flow aloft
will be in place over the Eastern Seaboard as we move into the short
term Sunday evening, with an upper trough dragging a surface low and
attendant front across the MS/OH Valleys. Some timing differences
especially with the GFS wanting to bring some warm frontal precip in
overnight, but by and large guidance is in fairly good agreement
with the front pushing in on Memorial Day. Temperatures will again
climb into the mid and upper 80s across the Piedmont with SBCAPEs
well over 2000J/kg and deep layer shear >40kts, and if you believe
the NAM, possibly higher. Steep low-level lapse rates and mid level
dewpoint depressions that would allow for dry air entrainment
accompany these parameters on forecast soundings, supportive of
damaging wind gusts. SPC Slight Risk for Day 3 covers a chunk of the
NW NC Piedmont, with marginal elsewhere. Main threats will be
damaging winds and perhaps large hail especially as the storms form
into a line, but cannot rule out isolated tornadoes if any storms
are able to get going ahead of the line, which certainly can`t be
ruled out. There might be enough shear with the system for embedded
weak tornadoes (there always seems to be something like that in our
area anyway) but again primarily damaging winds.

Front moves through Monday night into Tuesday and even with the
drier dewpoints, competition with downsloping at the base of the
upper trough will bring temperatures up just as high on Tuesday as
Memorial Day (but just not quite as oppressive right?). Can`t rule
out a couple of showers in the NW flow across the mountains Monday
night but have a dry forecast for now.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
As of 215 PM EDT Saturday: Upper trough remains in place over East
Coast as we move into the extended, with ridging in place over the
Plains. A dry pattern sets up with gradual cooling behind the front,
bringing temperatures back towards seasonal normals. A shortwave
moves across the flow Wednesday night into Thursday which should
serve to increase cloud cover just a tad, but for now have kept the
forecast dry. The Plains ridging begins to gradually shift east as
we approach the end of the period but timing on global guidance
varies on how quickly this occurs, so current forecast remains near
seasonal normals as finish out the work week.

&&

.AVIATION /19Z SATURDAY THROUGH THURSDAY/...
At KCLT and elsewhere: Scattered showers and thunderstorms expected
this afternoon and evening, so included a TEMPO at all TAF sites
based on the best timing and associated restrictions. Mid to high
clouds and debris continue to roam the area, but conditions are
expected to remain VFR outside of a thunderstorm. Winds remain out
of the southwest with some low-end gusts, but confidence is not high
enough for a mention in the 18Z TAF update. Shower and thunderstorms
will quickly dissipate after sunset and should allow for decent
clearing overnight. With tight dewpoint depressions and saturated
soils, expect for patchy dense fog to develop across the area,
especially in locations that receive rainfall. All TAF sites
indicate some form of vsby restrictions, but the major mountain
valleys maintain the highest confidence. Any lingering fog/low
stratus should burn off by mid-morning Sunday. A few mid to high
clouds will be possible during the daytime period Sunday, but
another round of showers and storms are likely around peak heating
or a little after. Will likely need a PROB30 mention in the 00Z TAF
update for most terminals.

Outlook: A unsettled pattern will linger thru the rest of the
weekend and into early next week, allowing for diurnal shower and
thunderstorm chances each day and at least patchy fog development
each night/morning.

&&

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

&&

$$

SYNOPSIS...TDP
NEAR TERM...CAC
SHORT TERM...TDP
LONG TERM...TDP
AVIATION...CAC