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000
FXUS62 KGSP 200553
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
153 AM EDT Sat Apr 20 2024

.SYNOPSIS...
Showers and thunderstorms are possible today as a cold front crosses
the area, with unseasonably warm weather through Saturday. Much
cooler temperatures and widespread light rain is expected Sunday
with drier weather on Monday. Drier and warmer weather will return
to the area Tuesday through next week.

&&

.NEAR TERM /THROUGH TODAY/...
As of 137 AM EDT Saturday: A thunderstorm lurks just to the
south of Greenwood County, but it was moving east and will only
shave underneath the edge of the fcst area. A remnant shower will
exit Union County NC in the next hour. Otherwise, the rest of the
overnight hours should be fairly quiet, altho a rogue shower could
still pop up anywhere as a weak frontal zone drops down over the
region thru daybreak. Temps should remain mild.

Otherwise, flat upper ridging will persist to our south while broad
upper troffing lingers to our north thru the near-term period. At
the sfc, a weak low is expected to develop over our southern
fringe and along a nearly stationary deformation zone early
Saturday. This low will eventually get pushed off the Carolina
Coast by the end of the period early Sunday as very broad high
pressure gradually spreads over our area from the NW. We`ll likely
see some brief sunshine late Sat morning/early aftn with mid and
high clouds increasing later in the day. Guidance still disagrees
wrt how much moist, low-level upglide will materialize over our
CWA during the latter part of Sat as the cold front stalls just
to our south. Most of the latest near-term guidance still keeps
the bulk of our fcst area dry thru the end of the period, so I
limit PoPs to solid chance across our southern-most zones. The
temperature fcst will be tricky. With better cloud cover and lower
thickness values expected for Sat, high temps should not be as
warm as the past few days, but they are still expected to top-
out above climo outside the mtns and just below climo over the mtns.

&&

.SHORT TERM /TONIGHT THROUGH MONDAY/...
As of 145 AM EDT Saturday: Baroclinic zone stretching from the Lower
MS Valley through the Southeast, while a stalled boundary sets up
shop over the Gulf Coast will help set the stage for increasing
PoPs on Sunday. A coastal wave will ride along the boundary and slip
east through S GA/Fl Panhandle during the daytime period Sunday. The
associated precip shield will overrun the entire CFWA, but lack of
instability should keep rain rates at bay, with light to moderate
QPF response. Factor in a strong surface high settling over the
Central High Plains, with a piece of the high breaking off over the
Mid-Atlantic, and an in-situ wedge will nose into the region with
north-northeasterly flow at the surface. Precip overriding this
stable dome will help to lock it in. As a result, temperatures
will run 15-20+ degrees cooler compared to Saturday. Most of
the rain should taper off by Sunday evening as the coastal low
shifts offshore, into the western Atlantic. High temperatures
for Sunday may occur early Sunday morning before the sun rises
as temperatures in the afternoon will struggle to get out of the
50s for most locations. In-situ wedge will lingering over the area
Sunday night into Monday before the surface high centers over the
area by Monday night. Overnight lows on Sunday will run on the cool
side as most locations are forecasted to run 5-10 degrees below
normal, but elevated winds at the surface ultimately shuts down any
frost potential across the active growing zones. Temperatures will
rebound slightly on Monday, but should remain ~10 degrees below
normal with continued north-northeasterly flow and colder air
aloft thanks to a quick moving shortwave trough that will swing
over the CFWA during the daytime period. Monday night will be the
coldest night as light winds and mostly clear skies lead to good
radiational cooling conditions. Tight dewpoint depressions and
temperatures should remain just warm enough to avoid any frost
development, but if trends lean slightly cooler between now and
then, the southern/central mountains of NC and the I-40 corridor
zones could end up with a Frost Advisory as overnight lows will
run 5-10 degrees below normal.

&&

.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
As of 215 PM Friday: By Monday night, the upper low slides off the
coast and guidance from the GFS and EURO show a strong upper low
churning over the Midwest/Canada region. This could bring a weak
boundary through the area Tuesday night, but nothing major is
expected at this point. Once that boundary lifts out of the area,
dry conditions return as a ridge builds back over the eastern CONUS.
As for any fire weather concerns, Tuesday may have some areas in the
Piedmont that reach the 30 percent thresholds for RH, but winds are
expected to remain light. Other than that, temperatures begin to
warm back up through the period. Tuesday night looks to be the
coldest with temps across the mountains, especially at the higher
elevations, hovering near or right above freezing. Frost/freeze
could be an issue, but will continue to monitor. Overall, the
pattern looks quiet, mild, and dry for now.

&&

.AVIATION /06Z SATURDAY THROUGH WEDNESDAY/...
At KCLT and elsewhere: Lingering showers have moved to the east of
the fcst area. The main concern this morning is the possibility
of ceiling/vis restrictions developing around metro Charlotte
in the pre-dawn hours, given the showers and storms that moved
through the region in the late evening. Some of the guidance has
picked up on this and paints a pessimistic picture with an IFR
ceiling restriction developing at KCLT before operations ramp up
this morning. I consider this almost a coin flip at this point,
so the TAF was written more optimistically and kept a TEMPO group
for some MVFR clouds before daybreak. Hopefully by the time
you are reading this, the atmosphere has shown its intentions
with regard to the low ceiling development. The mtns are the
other place where low level moisture could sneak in during the
pre-dawn hours. An MVFR-level cloud deck on the west side of the
mtns is expected to move up the valley to KAVL before sunrise,
resulting in a ceiling restriction. Wind will be light/variable
until a weak boundary moves thru, after which time light N to NE
is favored. On Saturday, the fcst looks relatively benign. Wind
should stay mostly N. A few of the models develop isolated storms
again in the afternoon, but the chance is too low to include in any
of the TAFs. Wind comes around to NE this evening and increases
as the next system approaches from the SW. For now, the arrival
of precip and moisture looks like it will be beyond the period,
but not so at KCLT, where some might reach by the end of the fcst.

Outlook: Rain and possibly isolated thunderstorms are expected
to develop on Sunday as a weak low pressure center passes just
south of our area, likely resulting in restrictions for at least
the southern part of our fcst area. Drier conditions return on
Monday and linger into Tuesday.

&&

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

&&

$$

SYNOPSIS...CP
NEAR TERM...JPT/PM
SHORT TERM...CP
LONG TERM...CP
AVIATION...PM