Area Forecast Discussion
Issued by NWS Greer, SC

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FXUS62 KGSP 191743

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
1243 PM EST Sun Nov 19 2017

Cool high pressure moves from east Texas to be over the
Carolinas by Monday evening as the wind becomes light. A weak cold
front crosses the area Tuesday night. Low pressure develops along
the Gulf Coast Thursday then moves up the Atlantic Seaboard through
Friday. Another strong cold front arrives next weekend.


As of 1235 PM EST Sunday: Radar echoes have all but dissipated
across the southern Appalachians early this afternoon, but cloud top
temps (per latest IR satellite imagery) continue to support ice
crystal nucleation, and KTNB recently reported -SN with reduced
visby. Small pops for high elevation snow showers have been extended
through about mid-afternoon.

Otherwise, skies will remain sunny/mostly sunny today for all but
the TN border counties, but even there cloud cover is expected to
gradually diminish into the afternoon. Highs will be 10 to 15
degrees below normal mountains and 5 to 10 degrees below normal
elsewhere.  Lows tonight will be around 10 degrees below normal
across the mountains and 5 to 10 degrees below normal elsewhere.


As of 220 AM Sunday: Short wave ridging over the area Monday moves
east Tuesday as a trough develops over the MS River valley. The flow
then splits as a northern stream short wave crosses the Great Lakes
and a southern stream short wave digs the southern end of the trough
to the Gulf Coast. At the surface, the center of high pressure
crosses the area Monday and into the Atlantic Monday night. The high
remains ridged into the area from the east on Tuesday. Southerly
flow develops between the high and a weak cold front moving into the
OH valley. Moisture does increase with this flow, but it is very
shallow. There is some insentropic lift, but it is also shallow and
relatively weak. There is some weak short wave energy crossing the
area but little to no deep forcing develops. The NAM is the fastest
with developing precip, so have trended later toward the other
guidance. This should keep p-types liquid with the later onset.
Still, PoP is limited to slight chance with very low QPF.

The cold front crosses the area Tuesday night with cyclogenesis off
the Carolina coast. There is some precip response mainly across the
I-77 corridor as a result. Again, the moisture is not deep and
forcing is weak. Therefore, have kept PoP in the slight chance range
with very low QPF. Drier high pressure begins to move in Wednesday.

Highs will be around 5 degrees below normal Monday and Tuesday then
rise to near normal Wednesday. Lows a little below normal Monday
night rise to a little above normal Tuesday night.


As of 130 AM EST Sunday: Guidance is finally beginning to come into
better agreement on overall pattern evolution around Thanksgiving.
Longwave troughing will dominate the east coast while a cutoff low
forms in the northern Gulf of Mexico late Wednesday through
Thursday. The exact track of this low remains uncertain, but trends
are now keeping it farther to our south hugging the N FL then SE
coast, keeping most of the moisture and QPF response out of our
forecast area. The moisture from this low will remain near the
Carolina coast for another day or two, with dry surface high
pressure able to work into our forecast area Friday as the upper
trough axis and a robust shortwave cross the Appalachians. An
Alberta clipper-type system will drag a cold front towards us late
Saturday and early Sunday, with cold air and deep upper troughing to
follow late in the weekend. At this point, any moisture associated
with the system looks quite anemic and confined only to our far
western mountain zones, where the possibility of light rain/snow mix
or a few snow showers is currently advertised.

After a chilly Thanksgiving with temperatures roughly 10 degrees
below average, highs and lows will moderate back to near climo
before the next cold front approaches late next weekend.


At KCLT and Elsewhere: Gusty winds will continue through the
afternoon at KAVL, while gusts have generally subsided at the other
terminals. Occl SCT stratocu in the 030-040 range will persist
through the afternoon at KAVL, while the other sites should remain
mostly clear/SKC through the period, although occl FEW/SCT clouds
around 050 are possible this afternoon. Winds diminish to less than
5 kts tonight, with directions likely becoming variable late. Winds
may return to the S/SW by the end of the period, as high pressure
pushes to the Carolina coast.

Outlook: Expect VFR conditions through Monday, under the influence
of cold/dry continental high pressure. Increasing low level moisture
could result in cig restrictions and perhaps -RA on Tue/Tue night.
Otherwise, dry/cool conditions should persist into late week.

Confidence Table...

            17-23Z        23-05Z        05-11Z        11-12Z
KCLT       High  87%     High 100%     High 100%     High 100%
KGSP       High 100%     High 100%     High 100%     High 100%
KAVL       High  94%     High 100%     High 100%     High 100%
KHKY       High 100%     High 100%     High 100%     Low   58%
KGMU       High 100%     High 100%     High 100%     High 100%
KAND       High  94%     High 100%     High 100%     High  83%

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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