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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS62 KGSP 242140
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
540 PM EDT Mon Sep 24 2018

.SYNOPSIS...
A wedge of moist high pressure will persist across the area into
Tuesday. A cold front will then move across the mountains Wednesday
and become stationary thru Thursday. This front will maintain a
chance of showers and thunderstorms each afternoon until dry high
pressure builds in Friday and lingers through the weekend.

&&

.NEAR TERM /THROUGH TUESDAY/...
As of 520 PM EDT: Breaks continue to occur in the overcast around
the edges of the wedge, but there`s not enough insolation to really
destabilize things. So thunder chances look close to zero at this
point and will be removed from the forecast. Otherwise, minor tweaks
to the hourly temps and sky thru this evening were made.

Otherwise, weak cold air damming will remain over the area tonight.
Despite some breaks in the clouds around the edge of the wedge,
expect clouds to return during evening and continue overnight. The
best coverage of showers this afternoon and early evening will be
west of the French Broad Valley and south into the Upper Savannah
River Valley where weak instability has developed. Shower coverage
will increase along and near the Blue Ridge escarpment overnight in
the continued moist upslope flow. Coverage decreases elsewhere. Lows
will be around 10 degrees above normal.

The low level flow turns more south then southwest through the day
Tuesday allowing the cold air damming to slowly erode and mixing
begin. Shower activity will continue to favor the mountains where PW
values and instability will be higher. Drier conditions will linger
outside of the mountains where a moisture minima develops and weak
subsidence moves in ahead of the weak tropical systems approaching
the Carolina coast. Low level thickness values increase with the
eroding wedge. This will combine with drier conditions and some
sunshine for highs to rise a few degrees above normal.

&&

.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY/...
As of 215 PM EDT Monday: With troughing over the central US and
ridging over the Atlantic, latest guidance continues to suggest a
weak sfc ridge across the Carolinas will be in the process of
retreating off to the northeast Tuesday evening, ahead of an
approaching cold front. Situated in between these two synoptic
features, SWly flow will allow for moisture to be infiltrated into
the Southeast as fcst soundings continue to suggest PWATs ranging
between 1.50-1.75", possibly increasing to near 2 inches. Anticipate
lingering isolated showers and thunderstorms Tuesday night into
Wednesday morning, mainly across the mountains, with coverage
becoming more widespread Wednesday into Thursday across the entire
FA, as the upper trough axis shifts eastward and becomes more
elongated, pushing the cold front into the FA from the NW. Some
guidance highlights dynamic support increasing on Thursday as the
now upper trough axis moves overhead and the cold front becomes
somewhat stationary over the Carolinas. With increasing noteable
instability and lower end shear values, would not entirely rule out
a few strong to severe tstorms throughout the short term forecast
period. Though, do anticipate more favorable conditions for severe
weather will remain well of to the north, as noted by the latest SPC
Convective Outlook. Temperatures throughout the forecast period will
remain above normal. With SWly flow keeping dewpoints in the 70s, it
will continue to feel more like Summer than Fall.

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
As of 245 PM EDT Monday: The extended forecast period kicks off
Thursday night as a cold front remains nearly stationary across the
area with lingering showers and thunderstorms. Per latest guidance,
anticipate this boundary to finally push out of the area on Friday
as the upper longwave trough continues to broaden and expand
eastward. Behind the front, flow becomes nearly zonal as an upper
ridge builds in over the Atlantic/Southeast, expanding westward into
the Gulf of Mexico through the weekend. With lower confidence on the
placement of the sfc high between the model guidance, will keep the
inherited trend of low end PoPs throughout the weekend - but am not
expecting activity to be as widespread/higher PoP as is expected
Wednesday and Thursday. Temperatures will remain slightly above
normal, but dewpoints will drop into the 60s Saturday and Sunday.

&&

.AVIATION /22Z MONDAY THROUGH SATURDAY/...
At KCLT and elsewhere: Conditions only slowly improving this
afternoon with some MVFR but quite a bit of IFR. Should see MVFR
cigs for all but KHKY later this afternoon. Expect MVFR to continue
into the evening with IFR and even LIFR developing overnight.
Showers most likely at KHKY and KAVL this afternoon and overnight
and this afternoon at the SC sites. Vsby will generally be VFR
except possibly MVFR is showers. IFR to LIFR vsby overnight at KAVL.
Any vsby restrictions quickly improve after daybreak Tuesday.
However, cigs will remain low with IFR for most of the morning and
MVFR into the afternoon. Winds generally ENE, with SE at KAVL.

Outlook: A cold front moving in from the west will then bring higher
chances of showers and storms Wednesday thru the end of the work
week.

Confidence Table...

            21-03z        03-09Z        09-15Z        15-18Z
KCLT       High  81%     High  90%     Med   79%     High  80%
KGSP       High  82%     Med   64%     Med   63%     Med   79%
KAVL       High  98%     Med   74%     High  87%     High  93%
KHKY       High  85%     Med   70%     High  94%     Med   76%
KGMU       Med   73%     Med   68%     Med   67%     Med   79%
KAND       High  91%     High  94%     Med   76%     High  85%

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...SBK
NEAR TERM...ARK/RWH
SHORT TERM...SGL
LONG TERM...SGL
AVIATION...RWH