Area Forecast Discussion
Issued by NWS Greer, SC

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FXUS62 KGSP 241720

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
120 PM EDT Mon Oct 24 2016

A dry cold front will cross the Carolinas today from the northwest.
In the front`s wake, strong high pressure will quickly build back
over the region and linger through the middle of the week. Another
frontal passage is expected on Thursday.


As of 120 PM EDT: Upper level divergence on the south side of a
broad mid Atlantic jetlet may produce a few, intermittent, thin
mountain cirrus clouds into tonight. Meanwhile, A back door cold
front will move southward through western NC by this evening and
then settle south of the forecast area overnight. Only a few
locations in sheltered northern mountain valleys appear cool enough
for any patchy frost formation, so no advisory is expected.

Otherwise, deep layer NW flow will continue, with heights rising and
the pressure gradient relaxing through Tuesday. Surface high
pressure will build over from the north behind the front and push
lower thicknesses into the region. Weak downsloping will
continue to provide some measure of warming east of the mountains
despite the falling thicknesses - with maximum temperatures fairly
close to climatology.


As of 305 am Monday, the short term fcst picks up at 12z on Tuesday
with broad upper trofing gradually moving off the New England Coast
as upper ridging slowly spreads farther east in the trof`s wake. The
guidance suggests that the ridge will deamplify as it spreads
eastward resulting in a more zonal pattern over the fcst area for
much of the period. By early Thurs, another upper trof will begin to
develop to our NW as the upper ridge amplifies over the Western
CONUS. At the sfc, a reinforcing Canadian high will be spreading
over the region by early Tuesday bringing more dry air to the
Carolinas. As the center of the high slides farther SE late Tues and
into Wed, a weak wedge pattern will briefly develop over the CWFA.
This pattern won`t persist for long as the next cold front will move
into the area by early Thurs and break down any lingering wedge
bndy. As for the sensible fcst, we can expect a dry fcst thru
Wednesday with POPs ramping up from the west as the front approaches
early Thursday. Temps should remain near, if not just below, normal
for late October on Tues and Wed.


As of 255 am Monday: the medium range fcst picks up at 12z on
Thursday with a fairly progressive upper lvl pattern expected thru
the period. By early Thurs, an upper trof axis will be crossing to
our north as strong upper ridging dominates the Western CONUS.
As we move into Friday, the upper trof is expected to lift NE and
up over New England as more zonal flow briefly sets up over our
region. Beyond this point, the long range models differ significantly
wrt the upper pattern evolution. The latest 00z GFS digs another,
deeper upper trof down across the Eastern CONUS over the weekend
and then develops an embedded H5 shortwave in the trof`s wake early
Monday. The 12z ECMWF keeps relatively zonal flow over the southeast
well into Sunday and then generates a stronger looking H5 shortwave
over the Northern Plains and moves it across the fcst area by early

At the sfc, a cold front will be moving into the CWFA from the west
Thursday morning. Models indicate a fairly quick fropa with weak
reinforcing high pressure moving in behind the front by late Thurs/
early Friday. Beyond this, the models diverge with the GFS bringing
another cold front down from the Great Lakes on Sat with strong high
pressure overspreading the region after the fropa and lingering well
into next week. The ECMWF is much slower developing a low and and does
not bring its associated front to our doorstep until late Sun/early
Monday. As for the sensible fcst, no significant changes were made
owing to the pattern uncertainty beyond Friday. I kept slight to solid
chance POPs for Thurs and early Fri with the best chances over the
higher terrain and foothills with forecasted QPF amounts remaining below
0.5 inches.


At KCLT: Deepening mixing just ahead of an approaching back door
front is toggling winds WNW, with a low-end gusts expected through
the afternoon hours. More solidly NW then NE flow is expected
overnight behind the front, with NE to ENE winds less than 10 kt
continuing through the end of period. Any clouds will be limited to
thin cirrus developing off the Blue Ridge.

Elsewhere: Thin cirrus developing in mountain wave cloudiness will
impact mainly KAVL to KHKY this afternoon and evening. NW flow is
expected at the NC TAF sites, with low end gusts, while WSW flow
initiall in the Upstate of SC will toggle NW then NE overnight
behind a passing back door front. Anticipate VFR conditions
throughout, with light NE to ENE winds across the foothills through
midday Tuesday, except more northerly flow in the French Broad
Valley around KAVL.

Outlook: Dry high pressure will persist over the Southeast through
Wednesday. Then a fast-moving cold front will cross the area
Thursday or Thursday night, but with limited moisture. Dry
conditions return for next weekend.

Confidence Table...

            17-23Z        23-05Z        05-11Z        11-12Z
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%     High 100%
KHKY       High 100%     High 100%     High 100%     High 100%
KGMU       High 100%     High 100%     High 100%     High 100%
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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