Area Forecast Discussion
Issued by NWS Greer, SC

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FXUS62 KGSP 150913

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
513 AM EDT Sun Oct 15 2017

Warm conditions will continue today, with rain chances beginning
to ramp up in the mountains this afternoon ahead of an approaching
cold front. The front will quickly move through the area tonight
and Monday morning. Considerably cooler and drier air will spread
over the region in its wake and linger for several days.


As of 505 AM EDT: Areas of dense fog have developed across the area
along with patchy low clouds. A couple of bands of stratocu have
developed and are moving north across the area. This could limit or
at least temporarily hinder dense fog formation across portions of
the area. Still, have issued a dense fog advisory for the Foothills
and Piedmont of NC and all of the Upstate and NE GA as there will be
many locations with dense fog for much of the morning. There will be
patchy dense mountain valley fog as well.

Ridging surface and aloft remain over the area today. Large scale
height falls will overspread the area tonight as a short wave moves
in from the NW. This wave pushes a cold front across the area
tonight as well. The wave and front weaken as they move into the
area. A narrow area of deep moisture moves in with the front.
However, there is little southerly flow ahead of the system and it
is a quick mover. Instability is limited as well keeping thunder
chances to a minimum at best. There is decent forcing along with
some upper divergence from the right rear entrance region of a jet
streak. Therefore, have gone with likely to categorical PoP across
the mountains where the moisture and forcing combine with westerly
upslope flow. Kept PoP in the 40 to 50 percent chance outside of the
mountains. Timing will be late afternoon early evening across the
mountains and late evening to overnight elsewhere. QPF will
generally be light, but moderate amounts are possible across the TN
border counties where upslope flow will be maximized. Highs will be
around 10 degrees above normal. Lows tonight will be around 10
degrees above normal outside of the mountains but about 5 degrees
above normal across the mountains where cooler air will begin
filtering in behind the front.


As of 245 AM Sun: Rain chances will taper off from northwest to
southeast Monday following the cold front, which models continue
to agree should exit the CWFA by 18z. Subsidence associated with
the incoming high pressure evidently is stronger than previously
depicted, suggesting near-zero chances of convection along the
boundary. Cold advection will produce modestly gusty winds during
the afternoon and will limit max temps to the mid-upper 60s over
the NC Piedmont and mountain valleys, and lower 70s in the Upstate
and NE GA.

Winds will relax Monday night and skies will be nearly clear;
min temps will be several degrees below normal, and patchy frost
still is anticipated in the colder spots. A Frost Advisory will
be considered as the event moves into the near term. Conditions
remain settled and cool Tuesday and Tuesday night. Slightly calmer
conditions Tuesday night will maintain radiational cooling potential
and perhaps result in mins even colder in some areas. Patchy frost
is expected to return for some of the area.


As of 300 AM Sun: Not really a lot to remark on during the
medium range period. In short, we`ll remain under the influence
of continental high pressure, with minimal moisture available
for cloud cover or PoPs. Max temps will moderate back to two or
three categories above normal by Saturday, though mins will be
only about a category above normal. A weak upper trough over the
Southeast does look to amplify as it moves east of Florida and
the Bahamas in the latter half of the work week, and with rising
heights over the central CONUS, a more sharply amplified pattern
does develop over the southern tier. This eventually will set the
stage for pattern change after the end of the period.


At KCLT and Elsewhere: Patchy MVFR to IFR cigs and vsby have already
developed early this morning. Expect conditions to deteriorate through
the night with IFR developing before daybreak. May even be LIFR
especially in the mountain valleys and NC Foothills and Piedmont.
Expect conditions to improve by mid-morning with VFR into the
evening. Precip associated with an approaching front may move in
toward midnight, so a PROB30 has been added at the end of the period
for all but KCLT. Light winds increase from the southwest through
the day then diminish in speed slightly during the evening. Winds
turn NW at KAVL before the end of the period.

Outlook: The cold front, with associated showers and restrictions,
will cross the region from the west late tonight through early
Monday. Much drier and cooler air will filter in behind the front
and linger through the week.

Confidence Table...

            09-15Z        15-21Z        21-03Z        03-06Z
KCLT       Low   36%     High  98%     High 100%     High 100%
KGSP       Med   60%     High  93%     High 100%     High 100%
KAVL       Low   31%     High  86%     High 100%     High  91%
KHKY       Low   56%     High  93%     High 100%     High 100%
KGMU       Med   69%     High  93%     High 100%     High  92%
KAND       Med   72%     High  86%     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...Dense Fog Advisory until 10 AM EDT this morning for GAZ010-017-
NC...Dense Fog Advisory until 10 AM EDT this morning for NCZ035>037-
SC...Dense Fog Advisory until 10 AM EDT this morning for SCZ001>014-


SHORT TERM...Wimberley
LONG TERM...Wimberley
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