Area Forecast Discussion
Issued by NWS Greer, SC

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FXUS62 KGSP 291447
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
1047 AM EDT Mon May 29 2017

.SYNOPSIS...
Warm and humid air will remain over our region today as high
pressure settles east of the Florida coast. A series of weak cold
fronts will cross the area through mid week. Stronger cold fronts
will the area for the weekend.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 1030 AM EDT Memorial Day: This update features some
substantial updates to pops, mainly to delay onset but then a fairly
rapid ramp-up this afternoon, increasing chances to likely. Probably
need categorical but still not 100% sure of areal coverage, so this
will do for now. RAP analyses once again initializing sbCAPEs way
too high but with full sun across most of the area late this morning
(some Cu across the mountains and beginnings of some cirrus
overspreading extreme western areas), CAPE values should start
picking up soon. Also see remnants of the MCV moving up the TN Valley
and even some mountain wave activity in the central-northern
mountains. Slight risk remains in place for generally the southern
half of the area and hires guidance all seems to want to fire
convection around 20z just east of the Blue Ridge and then spread
east from there.

Otherwise, a cold front will remain just west of the CWFA thru this
evening, as it is roughly parallel to deep layer west-southwesterly
flow. This flow will advect plenty of moisture into the region, and
may limit instability, as some of the debris cloudiness takes time
to dissipate. Guidance generally agrees on about 800-1500 J/kg of
SBCAPE by peak heating, with the NAM the lowest. Not surprisingly,
the NAM keeps the area dry until about 600 PM, then brings
convection in from the SW. If we manage to get more on the higher
end of the consensus for CAPE, bulk shear should be adequate for
some organized convection, mainly multicell clusters. With all that
said, it is looking like there`s a risk of a few severe storms. The
new Day 1 Convective Outlook still has a slight risk for most of the
area. PoPs will feature mainly chance to low-end likely in the SWLY
upslope areas. Temps will be a couple categories above normal.

With the west-southwesterly flow persisting tonight, there may be
some lingering convection will into the evening and overnight. But
overall, PoPs should taper down. Plenty of cloud cover and elevated
dewpts will keep temps above normal.

&&

.SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/...
As of 245 AM EDT Monday: The CWFA remains near the base of a trough
extending south form an upper low over Ontario. This keeps weak
cyclonic flow over the area as the axis of the trough moves in
Tuesday and across the area Wednesday. Expect isolated to scattered
mainly diurnal convection each day. That said, the best chance of
convection will be Tuesday as a weak short wave and upper jet max
cross the area in the cyclonic flow, and a weak cold front moves
through. Severe chances look to be lower than previous days as
instability is weak with shallow lapse rates and moderate at best
shear. Highs will be near normal with lows up to 5 degrees above
normal.

&&

.LONG TERM /THURSDAY THROUGH SUNDAY/...
As of 255 AM Monday: Zonal flow or flat ridging develops over the
area Thursday and remains in place Friday. Relatively dry high
pressure over the area Thursday will lead to minimal chances of
diurnal convection. The high moves offshore Friday allowing moisture
return to develop leading to scattered diurnal convection. Heights
begin to fall Saturday and Sunday as another upper low develops over
the NE. Waves rotating around the upper low help push a weak cold
front into the area Saturday which stalls Sunday. The increase in
moisture, forcing, and instability results in increasing chances of
scattered diurnal convection each day. Highs remain nearly steady a
little above normal each day. Lows remain nearly steady above normal
as well.

&&

.AVIATION /15Z MONDAY THROUGH FRIDAY/...
At KCLT and elsewhere: Update for the KCLT 15z AMD is mainly to
drop the PROB30 and narrow down the timing of TSRA in a TEMPO,
adding some gusty winds. Otherwise, VFR conditions are expected for
the most part thru the period. Thin cirrus and light NW wind this
morning will give way to low VFR cigs, as a cumulus field is
expected with bases around 4000-5000 ft. Scattered SHRA and TSRA are
expected to develop from late afternoon, with the greatest coverage
expected this evening. Winds should shift out of the SW (except
staying north at KAVL), generally in the 5-10 kt range.

Outlook: Primarily afternoon and evening TSRA are possible each
day, bringing periodic restrictions. Areas of morning fog and/or
low stratus may potentially develop especially where RA fell the
previous evening. This pattern will continue through at least the
end of the work week.

Confidence Table...

            14-20Z        20-02Z        02-08Z        08-12Z
KCLT       High 100%     High 100%     High 100%     High 100%
KGSP       High 100%     High 100%     High 100%     High 100%
KAVL       High 100%     High 100%     High 100%     Med   73%
KHKY       High 100%     High 100%     High 100%     High  95%
KGMU       High 100%     High 100%     High 100%     High  98%
KAND       High 100%     High 100%     High 100%     High  95%

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

www.weather.gov/gsp/aviation

&&

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

&&

$$
SYNOPSIS...RWH
NEAR TERM...ARK/TDP
SHORT TERM...RWH
LONG TERM...RWH
AVIATION...ARK/TDP



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