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000
FXUS62 KGSP 190742
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
342 AM EDT Fri Apr 19 2024

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

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 331 AM Friday: Some thicker mid-level clouds were being
picked up on radar moving over northeast GA. Can`t rule out a
few sprinkles, but the better chances for precip first thing this
morning will come from the shower activity that has developed ahead
of a weak upper wave and was moving into southeast TN and northwest
GA at this hour. Some changes to the onset time were already made
in earlier forecast updates, so only a few tweaks are necessary
now. Meanwhile, even farther upstream, we see the remnants of
the strong/severe storms from late this past evening. The radar
trend suggests a split of sorts, with stronger storms moving east
across the central Appalachians and another linear convective band
over west TN that looks like it will dive to our SW. That won`t
leave us with much in the way of precip coverage for most of the
morning. Thickening cloud cover will help to keep temps on the
order of ten degrees above normal this morning.

A lead short wave will move across the region this morning and
will take weakening showers mainly over northeast GA and the
Lakelands. After that, it might get a bit interesting across the
fcst area, with the possibility of afew thunderstorms, one or two of
which could be severe. Destabilization should occur in the middle
part of the day as morning cloudiness shifts eastward with the
passing wave. The RAP shows mainly 1000-1500 J/kg of sfc-based
CAPE, with a few pockets upwards of 2000 J/kg. Shear should
be enough to help organize whatever storms manage to develop,
with effective shear 40-45 kt in places. This leaves us with
a conditional prob of a few severe storms, if we can get a few
storms to develop at all. Differential heating and convergence
downwind of some of the higher mtns should be able to do that
trick, not to mention a weak sfc boundary coming down from the
WNW. Large hail would be one possibility as RAP profiles show
some decent CAPE in the hail growth zone and relatively strong
winds at the EL. Meanwhile, the dCAPE could get above 800 J/kg,
suggesting some strong thunderstorm outflows. Some of the CAMs at
00Z had brief updraft helicity streaks downwind of the mtns. Make
of that what you will, but it at least hints of some potential
for briefly rotating updrafts that would improve severe weather
chances. The entire fcst area is in a Marginal Risk on the Day1
Convective Outlook and this is reasonable. Temps should end up a
category cooler than yesterday if we get the convection by peak
heating. The weak front crosses the region this evening and takes
most of the precip with it, save for some lingering upslope showers
near the TN border. Temps should remain mild overnight.

&&

.SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/...
As of 200 AM EDT Friday: The near-term cold front is forecasted
to be well south and east by the start of the forecast period
as the frontal boundary stalls over the Gulf Coast. An active
baroclinic zone will develop across the Deep South/Gulf Coast
and help aid in widespread showers and thunderstorms in these
regions as a series of surface waves develop and ride along the
stalled front. Enough differential heating and a northward ripple of
the boundary due to a passing surface wave could set the stage for
isolated convection near the vicinity of the boundary Saturday
afternoon, mainly in locations along and south/east of I-85.
Otherwise, dry air entrainment will gradually filter in behind the
front and should allow for a pleasant day for most locations
Saturday. Highs will be 4-8 degrees above normal for highs across
the Piedmont, while near-normal values are expected across the
mountains. Model guidance are in decent agreement with developing a
weak coastal low along the boundary Saturday night into Sunday along
the east-central Gulf Coast. The current track has this feature
slipping across the S GA/FL Panhandle and offshore the Southeast
Coast. Bizarre in-situ wedge will settle in as the parent surface
high slides into the Southern Plains and a piece of this area of
high pressure breaks off and sets up shop over the Mid-Atlantic
Saturday night into Sunday. In this case, high temperatures will
drop ~15-20 degrees on Sunday compared to Saturday. The precip
shield associated with the coastal low will bring rainfall to the
area Sunday and essentially lock in any kind of wedge that develops.
QPF response will be light to moderate, with the southeastern zones
expected to receive the most rainfall.

The coastal low slips further offshore the Southeast Coast Sunday
night as the aforementioned parent surface high propagates
eastward and stretches from the Lower MS Valley through the
Mid-Atlantic. Cooler thicknesses will move over the area Sunday
night as a stout shortwave trough quickly shifts across the
central CONUS and knocking on our front door by the very end of
the period. Factor in continued north-northwesterly flow in the
low-levels and weak CAA, overnight lows are expected to be in the
40s for most locations, with values flirting with the 30s in the
higher elevations.

&&

.LONG TERM /MONDAY THROUGH THURSDAY/...
As of 315 AM EDT Friday: Lingering in-situ wedge is shown eroding
by Monday as the aforementioned surface high shifts across the
Carolinas and into the northeastern CONUS, while the shortwave
trough slips overhead and offshore by Monday night. This will
keep temperatures ~10-15 degrees below normal for most locations
Monday. Low-amplitude upper ridging will traverse across the CFWA
Tuesday into Wednesday, which will allow for the airmass to modify
as highs rebound to slightly below normal Tuesday to at or just
a tad above normal for afternoon highs on Wednesday. A potent
shortwave trough will move into the region later Wednesday into
Thursday with an attendant frontal boundary. Model guidance are not
excited about the potential impacts as the boundary will move into
a moisture starved environment and lack thereof forcing as better
forcing will reside north of the area. Best PoPs will stay confined
to the immediate Tennessee border before rain chances dwindle east
of the state line. Temperatures should remain near-normal through
the end of the week, with a mainly quiet pattern in store to round
out the extended forecast period.

&&

.AVIATION /08Z FRIDAY THROUGH TUESDAY/...
At KCLT and elsewhere: Prevailing VFR conditions at all terminals
through the period, but note that restrictions are possible in
showers and thunderstorms that develop this afternoon and early
evening. The latest guidance shows scattered storms after 17Z west
and 20Z east, thus we employ the PROB30 to handle the possibility
of MVFR in a 5-6hr window. The showers should get pushed east of
the fcst area by the mid-evening as a frontal boundary moves in
from the WNW. Expect a wind shift to W or WNW with the boundary
passge. Some upslope light precip could continue along the TN
border after dark and into the early morning hours Saturday.

Outlook: As a cold front sags south across the area, another round
of convection is possible Saturday, mainly during the afternoon.
Rain and possibly isolated thunderstorms are expected to develop
north of the front on Sunday, likely resulting in restrictions for
at least the southern part of the area. Drier conditions return
Monday, continuing into Tuesday.

&&

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

&&

$$

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