Area Forecast Discussion
Issued by NWS Greer, SC

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FXUS62 KGSP 010308
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
1008 PM EST Wed Nov 30 2016

.SYNOPSIS...
A cold front will move swiftly east across the region this evening.
Drier and cooler conditions will return tonight through Thursday and
persist through Saturday. Moisture should return from the west for
the latter half of the weekend and possibly linger into early next
week.

&&

.NEAR TERM /THROUGH THURSDAY/...
As of 10pm Wednesday:  Temperatures have begun to decline across the
area, though continued cloud cover has kept things warmer than model
guidance so far this evening.  As cloud cover continues to erode
tonight and after midnight, temperatures should decline more rapidly.

Line of convection ahead of a surface trough/deep upper wave has
exited the area and any chance for severe weather has exited with
it. Upper wave and front will pass through the mountains tonight
leading to dryer and cooler temperatures for Thursday.  High surface
pressure builds in from the west behind current system leading to
fairly benign weather with clear skies on Thursday and High Temps.
dropping 5 to 10 degrees on Thursday and another 5 degrees on Friday
to near normal.

&&

.SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY/...
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
Friday.

&&

.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
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 line...next 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.

&&

.AVIATION /03Z THURSDAY THROUGH MONDAY/...
At KCLT and elsewhere:  Line of heave showers is exiting the area
and is east of KCLT at this time.  The following 24 hours will be
free of precipitation and have reduced winds as surface pressure
increases behind a major frontal passage tonight.  Skies will also clear by
Thursday morning.  850mb winds of 40 to 50 kts will continue the
wind gusts up to 20 kts at higher elevation, but these should
decline to unnotable values by Thursday morning.  Winds will
generally be southwesterly around 10kts through thursday.  Chances
for fog in mountain valleys seems remote due to much dryer air and
some wind overnight.

Outlook: Dry high pressure returns in the wake of the front for
Thursday thru Saturday.

Confidence Table...

            03-09Z        09-15Z        15-21Z        21-00Z
KCLT       Med   76%     High 100%     High 100%     High 100%
KGSP       High  98%     High 100%     High 100%     High 100%
KAVL       High 100%     High 100%     High 100%     High 100%
KHKY       High  88%     High 100%     High 100%     High 100%
KGMU       High 100%     High  94%     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:

www.weather.gov/gsp/aviation

&&

.GSP WATCHES/WARNINGS/ADVISORIES...
GA...None.
NC...None.
SC...None.

&&

$$
SYNOPSIS...HG
NEAR TERM...WJM
SHORT TERM...HG
LONG TERM...LEV
AVIATION...WJM


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