Area Forecast Discussion
Issued by NWS Greer, SC

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FXUS62 KGSP 291745

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
145 PM EDT Wed Mar 29 2017

Dry high pressure will build into the area from the north through
tonight. Moisture will gradually increase through the day tomorrow,
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 week.


As of 145 PM EDT: Low clouds developing across the area but temps
remain quite warm. Going forecast looks on track.

Otherwise, the forecast remains on track with the departing surface
cold front continuing 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, especially over
western NC east of the Blue Ridge. This will herald the onset of
cold air damming conditions by daybreak Thursday.


As of 2pm EDT Wednesday: First of a series of strong dynamical
spring systems reaches the area Thursday night/Friday morning with a
round of showers and thunderstorms.  Current expectations are for
very marginal instability with CAPE below 500 j/kg and LI of -1,
combined with deep layer shear to 55 kts.  Showers and some thunder
are a good bet Thursday night/Friday morning, but severe potential
will depend on some improvement in parameters over what is now
forecast.  As the system moves eastward on Friday, diurnal warming
will increase instability, with improved chances for SVR as the
system exits out of eastern parts of the CWA.  Region should receive
useful amounts of rainfall with this first system Thursday night and
Friday morning with storm total rain amounts of around a half inch
to an inch, with locally heavier amounts with the deeper convective

Wedge/CAD regime in place on Thursday brings some low-level moisture
from the southeast into the area with some upslope showers in the
higher terrain.  Somewhat cooler air and CAD-related cloudiness will
limit the development of surface-based CAPE.  CAD will be disrupted
by wet passage of major frontal system Friday morning, with
low-level winds veering to westerly and eventually northwesterly
behind the front.  Frontal passage will be accompanied by gusty
winds, especially at higher elevations with 850mb winds of 30 to 40
kts. Passage of front will scour moisture and create drying
conditions for the balance of Friday and clearing by Saturday
morning; with fair weather on Saturday.

Temperatures on Friday will warm some over Thursday pre-frontal,
with post-frontal temperatures recovering rapidly on Saturday in
clear skies.


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 continue to build
down across the forecast area from the north today and persist
through tonight. Winds have toggled SE or ESE outside of the
mountains and SSE at KAVL. These winds will continue until this
evening when they toggle back to NE. They remain light SSE at KAVL.
Stronger ENE winds outside of the mountains and S wind at KAVL
expected Thursday morning. Low VFR clouds become BKN this evening
then lower to MVFR then IFR before daybreak as moisture increases
and upslope flow develops. Cigs lift back to low MVFR at KCLT but
remain IFR elsewhere with MVFR vsby developing as isentropic lift
and cold air damming wedge develops bringing rain and drizzle across
all but KCLT.

Outlook: Showers and thunderstorms develop over the SC sites and
possibly KAVL Thursday afternoon as the wedge weakens and
instability develops. The approach of a strong storm system will
bring continued chances of restrictions as well as a potential for
heavy rain showers and thunderstorms Thursday night and Friday.
Drier conditions will return again for the weekend.

Confidence Table...

            17-23Z        23-05Z        05-11Z        11-12Z
KCLT       High 100%     High 100%     High  94%     High 100%
KGSP       High 100%     High 100%     High 100%     High  93%
KAVL       High 100%     High 100%     Low   55%     Low   40%
KHKY       High 100%     High 100%     Med   72%     Med   71%
KGMU       High 100%     High 100%     High 100%     High  93%
KAND       High 100%     High 100%     High 100%     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:




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