Area Forecast Discussion
Issued by NWS Greer, SC

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FXUS62 KGSP 222325

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
725 PM EDT Sat Oct 22 2016

High pressure will build across the region over the weekend. A dry
cold front will move through on Monday...with strong high pressure
building back in through the middle of next week.


As of 730 pm Saturday: Winds continue a little gustier than the
going forecast, and dewpoints a little drier so have made another
round of adjustments to trends. Might make frost a little less
likely to develop but the advisory is out so will leave it. Did
tweak overnight lows just a tad but in the end the chances really
don`t make any differences to wording in the zone products, with
only a degree or two here and there.

Otherwise, building dry high pressure will provide clear conditions
across the western Carolinas and NE GA through Sunday. Winds are
forecast to weaken to a steady light NW wind overnight. Winds could
become occasionally calm near KCLT, KHKY, and KAND, possibly
allowing thin patchy frost to develop during the pre dawn hours. Low
temperatures are forecast to range from the low 30s across the mtns
to the upper 30s east. A noticeable thermal belt is expected across
the foothills, keeping temps in the low 40s. I will leave the Frost
Advisory in place.

On Sunday, near term guidance indicates that a shallow lee trough
will form during the mid morning hours, resulting in light SW winds
across the foothills and Piedmont by 15z. Light return flow should
remain through the rest of the day. Using a blend of guidance, I
will forecast a high temperature near 70 within the mtn valleys to
the low to upper 70s north to south across the foothills and
Piedmont. Afternoon RH values will generally range in the 20s,
highest east of I-77.


As of 215 PM Saturday, a series of short waves digging into the
northeast Conus will act to deepen the long wave trough along the
East Coast during the short term. This will send a dry/reinforcing
cold front into the area on Monday. Cold advection will initially be
rather weak and limited primarily to the mtns, with downslope flow
and anomalously high early day thickness values supporting max temps
of almost 10 degrees above climo Monday afternoon. Thicknesses are
progged to decrease enough by Tuesday such that temps should be very
close to climo Monday night through Tue afternoon. Otherwise, the
air mass will remain very dry, with nary a cloud in the sky expected
through the period.


As of 230 PM EDT Saturday...The main feature of interest in the
medium range is a fast-moving trough that will cross the CWFA
Thursday or Thursday night. An accompanying surface low pressure
system will organize over the Midwest on Wednesday, then deepen
gradually and stall over the Great Lakes Thursday into Friday. The
main difference between the 12z GFS and 00z ECMWF is that the GFS
doesn`t considate the upper trough as much as the ECMWF. The result
is that the ECMWF has more Gulf moisture inflow into the system and
has more DPVA across the southern Appalachians. So the GFS wrings
out only a few westerly upslope showers along the TN border. The
ECMWF has much more QPF response, but is probably overdone, even
with the greater moisture and forcing. So I trended toward the low
side of guidance for PoPs for Thursday into Thursday night, but this
still results in a slight increase from previous forecast. Even if
the ECMWF ends up being right, QPF will be fairly light. Otherwise,
the medium range looks dry with near normal to slightly above normal


At KCLT and elsewhere: VFR through the period. Primary just a wind
forecast with speeds around 10kt this evening with low-end gusts
subsiding to below 5kt overnight, and then picking back up again
between 5-10kt Sunday. NW winds overnight should back around to the
SW tomorrow as lee troughing sets up, with current timing for KCLT
between 12-14z.

Outlook: Dry high pressure will continue to spread across the
Southeast for the beginning of the week, with another reinforcing
Canadian High moving over the region on Tuesday.

Confidence Table...

            23-05Z        05-11Z        11-17Z        17-18Z
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:


GA...Frost Advisory from midnight tonight to 9 AM EDT Sunday for
NC...Frost Advisory from midnight tonight to 9 AM EDT Sunday for


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