Area Forecast Discussion
Issued by NWS Greer, SC

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FXUS62 KGSP 241426

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
1026 AM 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 1020 AM EDT: The main adjustment to the forecast this morning
has been for hourly temperature trends in areas just in the lee of
the mountains - where mixing and downsloping have led to fast
warming. Otherwise, the forecast remains on track with a dry
backdoor cold front expected to slip southward across the NC
Foothills and Piedmont during the late morning to midday period,
passing across Upstate SC during the early afternoon. Sfc winds will
veer as the front approaches through late morning. Only a few cirrus
clouds will be possible with the passage of the front. The timing of
weak CAA in the wake of the front will favor temps climbing up to
two categories above normal, but still well below records. High
pressure will build back in from the NW behind the front tonight,
but temps are not expected to be as cool as the air mass was behind
the last front. At this point, the frost threat looks minimal.


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 and elsewhere: VFR conditions expected through the TAF
period. A dry cold front will slide southward across the western
Carolinas during the afternoon, complicated by the development or
presence of a lee trof. With little moisture to work with, only a
wind shift is expected with the fropa. Winds will shift from SW to W
or WNW by midday, then veer further to NW this evening. The biggest
problem will be a cross-wind at KCLT through the middle part of the
day. Have opted to keep wind direction WSW thru much of the daytime
hours because of the lee trof, with a shift to WNW after 18Z based
on LAMP and RAP guidance. Only a few wisps of cirrus will stream by
from the west periodically through the period. The other trouble
spot has been KAVL. Strong winds aloft this morning above a strong
temperature inversion resulted in a few hours of low level wind
shear. However, the shear now appears to be going away as the
boundary layer continued to deepend and NW gusts begin.

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...

            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%     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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