Area Forecast Discussion
Issued by NWS Greer, SC

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FXUS62 KGSP 010551

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
1251 AM EST Thu Dec 1 2016

Drier and cooler conditions are in store today, and will persist
through Saturday. Moisture should return from the west for the
latter half of the weekend and possibly linger into early next week.


As of 1250 AM Thu: The surface cold front is presently over
the eastern third of the CWFA, but should gradually depart the
area between now and sunrise. Low clouds remain over the greater
Charlotte metro attm, but these will thin as the low levels dry. The
temp trends thru the early morning were a little off, assuming a
faster fropa; I have adjusted values thru 12z based on short-term
consensus product which is doing a reasonable job so far. Some
upslope clouds will persist along the Tenn border into the day,
but otherwise mostly sunny skies are expected. Max temps will be
near normal.


As of Noon EST Wednesday: Zonal flow will be in place aloft across
the eastern CONUS Thursday night through Friday. Meanwhile, shallow
NW flow moisture may persist along the TN border in the northern
mountains into Friday, but will carry no PoPs given the weak WNW
upslope character and very shallow moisture. Cold temperatures would
support flurries or snow, however, if more moisture arrives than
progged. Otherwise, surface high pressure will gradually build east
toward the Appalachian chain and keep profiles dry across the region.

A broad but shallow ridge will then develop through Saturday across
the southeast. Although model differences persist with the expected
upstream low pressure development across TX and the western gulf
coast, there is good agreement on little if any upglide moisture
returning through 00Z Sunday. Will thus keep the forecast dry
through Saturday afternoon. Temperatures Friday through Saturday
will be near to just below climo, slightly cooler Saturday than


As of 230 PM EST Wednesday...the medium range portion of the
forecast continues to be plagued with uncertainty among the global
models. The extended period kicks off 00z Sunday with our area under
a weak upper ridge, with a surface high centered over the OH River
Valley and an upper low over the Baha Peninsula. A plume of moisture
associated with a gulf surface low begins to extend into the CWA
overnight Saturday, with pops ramping up to the chance category by
Sunday morning.

Models diverge at this point on the handling of the progression and
depth of the upper low as it ejects out of the desert Southwest,
which has fairly significant implications as far as pops/QPF in our
area. As WPC mentioned in today`s extended discussion, the faster
ECMWF has displayed poorer run-to-run consistency than the GFS, so
confidence is generally higher in the 12Z GFS solution and the
forecast is weighted more heavily toward it and its ensemble mean,
which is also in relatively good agreement on the handling of the
upper low.

The first possible round of rainfall, associated with a gulf low and
weak front, will arrive Sunday night and last into Monday morning.
There may be a brief lull in the precip Monday during the day before
the upper low ejecting from the desert southwest develops a surface
reflection and frontal structure, and ramps up rain chances Tuesday
once again. Another lull in pops in anticipated Wednesday before
another frontal system arrives Thursday, though confidence in this
lull is low enough that low-end chance pops are carried through the
entire extended period. Bottom week looks like it will
favor a rather wet pattern, though QPF totals are uncertain for the
time being. The temperature forecast is also uncertain to say the
least at the moment, though there is a good feeling that the medium
range will begin with temps about 5 degrees below normal. A
moderating trend back to average seems like the most likely solution
for the rest of the extended period at this point, though there are
some hints at much colder air arriving over the area towards the end
of the next work week, with some mixed precip possible over the
higher terrain. This will of course be re-evaluated in future
forecast cycles.


At KCLT: Cold front is oriented NE-SW across the Carolina Piedmont,
not quite yet thru KCLT. Patchy MVFR cigs remain in that area but
are expected to dissipate 08-09z. Winds are taking their time
to veer in the wake of the front; expect a shift to WNW around
daybreak. Lee troughing appears likely to bring winds back to WSW
for a time there this aftn.

Elsewhere: VFR as colder/drier air filter in on W to NW winds;
some upslope cloudiness will linger over the mountains this
morning. Where winds remain more westerly, they should veer more
NW this evening. Some occasional gustiness is possible around the
area today within the CAA pattern, but gusts are only expected to
be significant at KAVL.

Outlook: Dry high pressure persists over the region thru
Saturday. Precip and restrictions may return as soon as Sunday,
as another cold front moves into the region. There may be a brief
lull in these impacts Monday, before low pressure develops along
the front to our west and brings a second shot of moisture overhead
Mon night into Tue.

Confidence Table...

            06-12Z        12-18Z        18-24Z        00-06Z
KCLT       High  80%     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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