Area Forecast Discussion
Issued by NWS Greer, SC

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FXUS62 KGSP 290731

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
331 AM EDT Wed Mar 29 2017

Dry high pressure will build south from eastern Canada along the
east coast today. Moisture will gradually return on Thursday, with
abundant moisture in place by Friday as a strong low pressure system
moves east from the Mississippi River Valley. Drier weather will
return for the weekend with unsettled weather returning early next


As of 250 AM EDT: The departing surface cold front will continue to
settle southward across central Georgia and extreme southern SC
today as sprawling surface high pressure builds down from the
eastern Great Lakes. Meanwhile, a vigorous closed low pressure
system over the southern plains will deepen today and enhance
downstream ridging over the southeastern U.S. Good insolation and
only limited thickness falls behind the front in our area will
permit temperatures to once again reach into the lower 80s in much
of the foothills and piedmont across northeast GA and Upstate SC,
with plenty of 70s elsewhere.

Under continued ridging aloft, 850 mb moisture will begin pooling
east of the Blue Ridge late today, and southerly upglide forcing and
moisture will develop tonight over the surface ridge. This will
permit light rain or drizzle to begin breaking out, especialy over
western NC east of the Blue Ridge. This will herald the onset of
cold air damming conditions by daybreak Thursday.


As of 230 AM EDT Wednesday: A moist wedge will continue to build in
across FA early Thu. Models show good moist flow persisting off the
Atl thru the day atop atop the cold dome which will instigate showers
rather quickly across the nrn wedge front which will expand across
most zones thru the afternoon. Qpf amounts will be light with the
higher amounts aligned mainly along and southeast of the BR. There
will likely be some differential heating along the srn periphery of
the wedge front where general tstms are possible. The better
instability shud remain southeast of this area. Max temps will vary
widely across the area with the nrn zones hitting arnd 60 and mid
70s realized across the srn zones. With good cloud cover and
continued precip...low temps will only drop off 10-12 degrees.

The Fri period still looks interesting beginning early on. A strong
dynamical system will approach from the west and begin to break
down the wedge aft 06z likely creating a retreating TMB
scenario. Bulk shear will increase to arnd 50 kts along the srn
end of the bndry while MUCAPE values increase to near moderate
levels while mlvl lapse rates steepen to near 7 C/km. Bufkit
soundings show very good 0-1 km helicity near the sfc bndry as rotating updrafts will be possible. Thus...will keep
with the previous trends and fcst tstms early on...some of which
could become stg/svr before daybreak across the srn zones.
Strong convec activity will likely continue into the early
afternoon while developing east and north. There is a little
concern with the deep h5 trof advancing a well defined s/w
across the nrn GOM and perhaps producing moisture robbing
convec...yet there shud be enuf large scale forcing and residual
llvl Atl moisture to produce and maintain convec south of the
TMB ahead of an incoming cold front. The cold front looks to
cross east of the area by the middle of the afternoon...clearing
convec activity as upslope -shra lingers across the mtn spine
on the back side of the sfc low. Will keep the same severe
mention in the HWO as far as timing and areas affected.


As of 315 AM EDT Wednesday: Not much change from the previous fcst.
The models continue to show good agreement with small scale h5 ridge
crossing the SE CONUS over the weekend. This will bring dry conds as
a sfc high builds across the mid-atl region. Good insol and nw/ly
downslope flow will enable max temps Sat to reach a cat or so above
normal. Winds will shift se/ly Sun and good insol will again allow
max temps similar to Sat/s highs. Both days will be rather pleasant
as dewpoints remain in the U40s.

Another storm system will affect the area Mon thru Tue. There
doesn`t look to be too much precip coverage during the day Mon with
mainly mech lift -shra...but the overnight will see a warm front
cross to the north. There shudn/t be too much instability due to the
nocturnal timing...but soundings indicate MUCAPE of arnd 700 J/kg
early Tue thru mid morning. Combined with good deep layered
shear...this period could be under the gun for stg to svr tstms.
A dry slot will likely push in from the SW quickly limiting more
stable precip across the upslope regions and perhaps lingering tstms
across the NW Piedmont thru 21z. Max temps Mon should be right arnd
normal or a couple degrees above with highs warmer by a cat on Tue
in developing sw/ly flow.


At KCLT and elsewhere, surface high pressure will build down across
the forecast area from the north today and persist through tonight.
Expect generally NE winds east of the mountains, but with continued
NW upvalley flow at KAVL through the morning hours. Winds will
gradually come around to a southeasterly direction throughout by
midday, and FEW to SCT VFR clouds will start to form as 850 mb
moisture begins pooling east of the Blue Ridge. The main concern for
any restrictions through the period will be mountain valley fog,
primarily in valleys south of KAVL, around daybreak this morning.
VFR cigs will develop tonight as upglide forcing and moisture
improve, but restrictions look to be just beyond the current period.

Outlook: Moisture returning above a developing cool surface wedge
could result in low clouds and light rain across the area on
Thursday. The approach of a strong storm system will bring continued
chances of restrictions as well as a potential for heavy rain
showers and thunderstorms Thu night and Friday. Drier conditions
will return again for the weekend.

Confidence Table...

            07-13Z        13-19Z        19-01Z        01-06Z
KCLT       High 100%     High 100%     High 100%     High  92%
KGSP       High 100%     High 100%     High 100%     High 100%
KAVL       Low   55%     High 100%     High 100%     High 100%
KHKY       High 100%     High 100%     High 100%     High  97%
KGMU       High 100%     High 100%     High 100%     High  92%
KAND       High 100%     High 100%     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 and ensemble forecasts
are available at the following link:




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