Area Forecast Discussion
Issued by NWS Greer, SC

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FXUS62 KGSP 211823

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
223 PM EDT Fri Oct 21 2016

Cool high pressure will continue to be in control of our weather
through the middle of next week. After having below normal
temperatures this weekend, temperatures will warm a bit going into
next week.


As of 220 PM, the sfc cold has pushed east of the CWA as high
pressure remains centered over the southern Great Plains. I will
update the forecast to adjust sky and temps. The pressure gradient
across the southern Appalachians will start out ranging from 6-7 mbs
this afternoon/evening, then decreasing to 4-5 mbs during the
predawn hours tonight. Gusty northwest winds will continue across
the southern Appalachians through tonight.

As of 1030 am: The HRRR and NAM12 show a pressure kink in the lee of
the mtns, suggesting a mtn wave will remain through most of daylight
hours. Latest vis sate loop shows some wave clouds over the adjacent
foothills from Caldwell south to Polk Co. Given daytime mixing and
support from a 6-7 mb pressure gradient across the mtns, I have
highlighted the gust winds with a Wind Advisory across the east
facing slopes and adjacent NC foothills hills through 6 PM.
Grandfather Mtn., with a high elevation site, had a gust to 65mph
last observation. Otherwise, a shallow cloud deck exist across
middle and eastern KY/TN under deep dry air. Moist llvl NW flow
should support iso to sct showers along the TN/NC line through much
of the day. Otherwise, the region will remain dry and cool.

630 am update: the cold front has been steadily pushing eastward
across the NC mts early this morning accompanied by scattered rain
showers. Winds are just now starting to veer around to NWLY over
far western NC and increase in speed. Otherwise, the fcst is still
pretty much on track for the rest of today and tonight.

As of 320 am Friday: precip has been fairly slow making its way
into the CWFA early this morning. So far, it has been confined
to the NC/TENN border zones. Cloud cover should continue to
increase thru the morning hours as the cold front pushes farther
east. Overall, the most recent model guidance is trending drier
with this fropa. Likely to categorical POPs are confined to the
NC/TENN border counties with slight to solid chance elsewhere.
By 00z Saturday, drier air will be advecting into the CWFA behind
the front and POPs dwindle. Winds will be gusty today and are
expected to remain out of the NW and blustery, especially over
the higher terrain, well into Saturday. By midday today, wind gusts
are expected to reach the upper 30s kts across the high terrain
and east facing mtn slopes. The strongest gusts will likely occur in
the wake of the mtns, with the forecast development of a mtn wave.
Based on the latest model guidance, I`ve lowered wind speeds a bit
from the previous fcst. Thus a Wind Advisory should not be needed,
however we will monitor trends if the guidance trends upward.
Otherwise, temps will be considerably cooler today and tonight with
highs and lows nearly 20 degrees cooler than yesterday.


As of 230 AM EDT Friday...the balance of the weekend looks cool and
relatively quiet, although Saturday should be a bit breezy. Think
any lingering small chance of precip will not linger past the middle
part of Saturday morning...thereafter sky will gradually clear
across the NC mtns. The main story will be the high temps...which
will be on the order of 7-10 degrees below normal...under a mostly
sunny to sunny sky. This will finally make it really feel like
Autumn across the region at long last.

The axis of the upper ridge will remain to our west through the rest
of the weekend, which will keep the wrn Carolinas under a cool NW
flow, and will support surface high pressure moving across the
Southeast. This should yield another seasonally cool night on
Saturday night with temps getting cold enough for more widespread
frost across the mtns once the wind dies down toward daybreak on
Sunday. There could even be some patchy frost outside the mtns in
the normally cooler and sheltered spots. Temps will moderate quickly
on Sunday afternoon...returning to near normal under sunny sky...and
will not be nearly as cold Sunday night ahead of a reinforcing cold
front dropping down from the NW.


As of 220 PM EDT Friday...starting with Monday evening with an upper
trough over New England and a ridge axis from Texas cross the
Dakotas. Surface high pressure centered over Chicago at that time.
A cold front will be crossing our region from north to south ahead
of this high pressure transiting to across the lower Great Lakes
and Ohio Valley. This front crossing early in the week should
certainly be dry. A trough arriving on Thursday will have some
amount of moisture and if the ECMWF model is correct then all rain
would pass us to the north.  The latest GFS has a 500mb closed low
forming over Wisconsin at 18Z Wed and moving SE toward our area on
Thursday. With this GFS solution, first moisture arrives in the NC
Mtns Thursday AM with at least some rain over the entire forecast
area late Thursday and Thursday night. This closed low opens up over
VA on Friday as all precip moves out to the east. At this point we
will slightly increase POPs and certainly increase some cloud cover
for Thursday into Friday.  Temperatures will be very close to normal
through this medium range period.


At KCLT and elsewhere: As of 220 PM, the sfc cold has pushed east of
the CWA as high pressure remains centered over the southern Great
Plains. The pressure gradient across the southern Appalachians will
start out ranging from 6-7 mbs this afternoon/evening, then
decreasing to 4-5 mbs during the predawn hours tonight. Gusty
northwest winds will continue across the southern Appalachians
through tonight. Recent satellite images shows a wide field of low
clouds across eastern and middle KY/TN. Moist NW flow should support
light showers near the TN/NC line through late tonight, ending
before sunrise Sat. However, cloud cover will remain thick across
the TN border counties, possibly reaching KAVL from time to time.

East of the mtns, winds will weaken across the Piedmont shortly
after sunset, one or two hours later across the foothills. Steady NW
winds expected through the rest of the night. Mixing and remaining
pressure gradient will support marginal gusts developing by mid
morning, remaining through the rest of the day. VFR conditions

Outlook: Dry high pressure will then spread across the region on
Sunday and linger into early next week.

Confidence Table...

            18-24Z        00-06Z        06-12Z        12-18Z
KCLT       High  92%     High 100%     High 100%     High 100%
KGSP       High 100%     High 100%     High 100%     High 100%
KAVL       High  99%     Med   79%     Med   74%     High 100%
KHKY       High 100%     High  92%     High 100%     High 100%
KGMU       High  85%     High 100%     High 100%     High 100%
KAND       High  85%     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:


NC...Wind Advisory until 6 PM EDT this evening for NCZ033-049-050-


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