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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS62 KGSP 312125
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
525 PM EDT Tue Mar 31 2020

.SYNOPSIS...
A low pressure center moves east and off the Carolina coast
tonight.  Canadian high pressure slowly builds into the region
through Friday. A weak cold front moves through on Sunday.

&&

.NEAR TERM /THROUGH WEDNESDAY/...
As of 515 PM Tuesday: precip has ended across most of the fcst area
over the past few hours, with just some lingering light showers over
our far eastern zones and the wrap-around precip over the NC/Tenn
border region. Cigs also remain VFR across most sites with a thick
stratus deck in the 4 to 6kft range covering most of the CWFA. I
still expect another round of light showers late tonight and into
the overnight, however coverage appears to be trending downward with
each new run of the CAMs/mesoscale models.

Otherwise, low pressure is set to pass just south of the CWA early
this evening, supported by a shortwave trough moving east across the
lower Ohio Valley. A relatively dry sfc airmass remains in place
across Virginia and the Carolinas. Warm upglide did produce very
light precip into this airmass earlier today, but not apparently
enough so to lock in CAD as previously expected. A second round of
precip should occur this evening as the shortwave itself drifts
overhead. Confidence is not particularly high in the temp/dewpt/sky
fcsts through tonight east of the mountains. Temps are currently
fcst to fall near normal in the Piedmont, but likely won`t fall as
much if the clouds are more stubborn than fcst, due to the wedge.

Ah, yes, the mountains. What a story. With the moistening aloft
having not been as quick as expected, that left an opportunity
for the heavier precip to diabatically cool the midlevels, which
resulted in some high-elevation snow and sleet already today. Temps
at the higher elevations will remain cool enough for some wintry mix
into early evening, when they begin to really drop with CAA behind
the shortwave; the event turns to NW Flow at that time too. Snow
ratios won`t be all that good assuming the moist layer is as
shallow as depicted on prog soundings, but the upslope enhancement
should produce modest totals at the highest elevations, where temps
are cold enough the longest. Locations above 5000 ft likely will
see more than 2 inches total, but that area is too small for an
advisory. We will issue a Special Wx Statement to cover the threat.
The NW flow snowfall should taper off gradually thru the morning.
Except perhaps for some diurnal cu trapped under a low inversion,
skies will clear out across the Piedmont. However, max temps still
look to be 7 to 10 degrees below climo in that area, and under
continued CAA the high elevations may struggle to get into the lower
40s.

&&

.SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY/...
As of 100 PM EDT Tuesday: After the cold front/low pressure system
clears the area by the start of the short term period 00Z Thursday,
a generally quiet pattern will return. Surface high pressure
centered over the Great Lakes will slide southward on Thursday and
Friday before moving off the east coast. Upper heights will rise
just a bit both days as a low-amplitude upper ridge moves towards
the east coast, with max and min temps rebounding to right around
average by Friday afternoon. Temps Thursday morning will be just
below freezing in the high peaks and in the mid 30s for most mountain
zones, but will remain in the high 30s to low 40s elsewhere. Enough
of a N/NErly breeze is expected through Thursday morning that frost
shouldn`t be an issue in any active frost/freeze zones. Lows
Thursday night/Friday morning will increase to near normal, so no
frost/freeze concerns anticipated.

&&

.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
As of 145 PM EDT Tuesday: The medium range picks up Friday night
with the area still under the influence of weak surface high
pressure and muted ridging aloft. Saturday should remain dry as well
before a weak upper shortwave and surface front cross the forecast
area Saturday night. Current model guidance actually indicates very
little in the way of available moisture on Saturday night, so only
slight chance to  low-end pops were introduced. A frontal boundary
may activate over the area Sunday and increase rain chances, but
deep moisture and forcing are somewhat lacking, so just chance pops
were added Sunday. A more substantial shortwave will move across the
area Monday into Tuesday, with a better chance for more widespread
rainfall early next week. The pattern just beyond the end of the
medium range will remain unsettled. Upper ridging over the eastern
CONUS will keep max and min temps about 5 degrees above average
through early next week.

&&

.AVIATION /22Z TUESDAY THROUGH SUNDAY/...
At KCLT and Elsewhere: Confidence low in this set of TAFs given
poor performance of guidance so far today, with quasi-CAD event
yet to really unfold. Precip did develop on the warm side of a
fast-moving low pressure system, but it has had trouble really
locking in the wedge airmass, which was expected to produce
widespread IFR this afternoon. Current expectation is that cigs
will mostly stay VFR until next round of precip arrives late
this aftn and evening beneath upper shortwave. That still likely
will cause most of the area to drop to IFR for a portion of the
night as CAD finally develops, with drier and colder air scouring
that out later in the night. The remainder of the period will see
SCT-BKN low VFR stratocu. Winds will be mainly in the NE quadrant
across the Piedmont this aftn (SE at KAVL), backing to NW tonight
following the wedge. Some gustiness will occur at times. The higher
terrain near the Tenn border will see rain and snow showers late
this afternoon through early Wednesday within NW flow, but these
do not look likely to affect KAVL except perhaps to generate an
occasional MVFR-level cloud deck.

Outlook: VFR will return with dry high pressure on Wednesday and
Thursday, possibly lasting through the weekend, though return flow
ahead of the next system may bring nighttime and early morning
restrictions to parts of the area Saturday night.

Confidence Table...

            21-03z        03-09Z        09-15Z        15-18Z
KCLT       Med   70%     Low   56%     High  96%     High 100%
KGSP       Med   68%     High  81%     High 100%     High 100%
KAVL       Med   71%     Med   78%     High  86%     Med   74%
KHKY       Med   75%     Med   68%     High 100%     High 100%
KGMU       Med   68%     High  93%     High 100%     High 100%
KAND       High  90%     High  93%     High 100%     High 100%

The percentage reflects the number of guidance members agreeing
with the scheduled TAF issuance flight rule category. Complete hourly
experimental aviation forecast consistency tables are available at
the following link:

www.weather.gov/gsp/aviation

&&

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

&&

$$
SYNOPSIS...DEO
NEAR TERM...JPT/08
SHORT TERM...17
LONG TERM...17
AVIATION...JPT/08