Area Forecast Discussion
Issued by NWS Greer, SC

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FXUS62 KGSP 160734

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
334 AM EDT Mon Oct 16 2017

Light rainfall chances peak this morning as a fast-moving cold
front moves through the area.  Dry conditions and below-normal
temperatures will follow the front beginning this afternoon, and
persist through mid-week.  Warmer temperatures will return later
this week as deep-layer ridging sets up over the Southeast US.


As of 320 AM Mon: Wind shift line of incoming cold front as crossed
the Appalachians. A band of rainfall now near the TN/NC border
is expected to make progress east of the mountains, but potential
still exists for new development downstream. Short-term progs of
MUCAPE reflect slight destabilization downstream of the mtns as the
wind shift line moves in there, so an uptick in shower coverage
is expected before daybreak over the Upstate and NW NC Piedmont
even if the upstream band fizzles. Thunder chances are too low to
mention, with no strikes seen on the networks lately. Consensus
still depicts the post-frontal moisture exiting the CWFA to the
southeast by early afternoon.

Northwesterly gusts have already been reported from time to time
over parts of the mtns, and some gusting will develop later today
over the remainder of the area. With cold advection taking hold
early in the day, I used our short-term consensus product to come
up with hourly temp trends and based max values on that. Trends
will be least diurnal in the mtns but peak a bit earlier than
usual in the Piedmont as well. Tonight, winds will remain breezy
as skies become virtually clear. Bias-corrected MOS temps did
well with the "cold snap" we had at the beginning of the month,
so those were preferred for tonight`s mins. Conditions should
be sufficiently moist for some patchy frost to form in the mtn
valleys and foothills, though wind may promote enough mixing to
keep it localized. Hence no advisory will be raised at this time;
day shift will take a second look.


As of 220 AM EDT Monday: Short wave ridging develops over the
Southeast Tuesday before a weak trof returns for Wednesday. At the
surface, cool and dry high pressure builds in Tuesday and remains in
place for Wednesday. Clear skies and light winds will lead to lows 5
to 10 degrees below normal both nights. This puts the mountain
valleys in jeopardy of frost development both nights and the
Northern Foothills and NW Piedmont in jeopardy Tuesday night. Highs
around 5 degrees below normal Tuesday rise to within a couple of
degrees of normal Wednesday.


As of 305 AM EDT Monday: An upper ridge axis builds over the area
through Saturday. At the surface, high pressure remains over the
area Thursday and Friday before sliding off shore on Saturday. This
results in dry weather with a warming trend. Highs start out
Thursday a couple of degrees above normal and rise to around 5
degrees above normal for Friday and Saturday. Lows start out a
little below normal and rise to a little above normal. The ridge
axis moves to the Atlantic coast or off shore on Sunday as deep trog
develops over the central CONUS. The guidance is in some
disagreement on how this trof develops. Both the GFS and ECMWF
develops a closed low at the base of the trof near the Gulf Coast.
However, the GFS is farther west as the northern stream wave splits
and moves east faster. The ECMWF keeps the streams more coherent and
is farther east with the closed low. This shows up at the surface as
the GFS holding the surface ridge in a little longer keeping our
area dry as the moist southerly flow is farther west. The ECMWF
breaks down the ridge allowing the moist southerly flow to move in
from the west faster. Given the differences, have kept Sunday dry
for now. Lows will be a little above normal with highs around 5
degrees above normal.


At KCLT and Elsewhere: A cold front will push through all terminals
this morning. Wind shift to NW has already occurred at KAVL and
will progress NW-SE across the area, happening at KCLT last, around
daybreak. Showers will accompany the front, with occasional MVFR
cigs and vsby. Though a wide band of VFR to MVFR stratus is present
behind the wind shift line over KY/TN, downsloping is expected to
keep this somewhat at bay, so TAFs reflect fairly rapid improvement
to VFR following end of showers. Some gustiness will occur today
as colder air filters in, particularly at KAVL. Clear skies and
NW to N breezes tonight; frost formation is a possibility at KAVL
and other mtn valley locations.

Outlook: Seasonably cool, dry, and overall VFR conditions will
persist through the work week.

Confidence Table...

            07-13Z        13-19Z        19-01Z        01-06Z
KCLT       Med   71%     High  91%     High 100%     High 100%
KGSP       High  81%     High 100%     High 100%     High 100%
KAVL       Med   68%     High  81%     High 100%     High 100%
KHKY       High  82%     High 100%     High 100%     High 100%
KGMU       High  92%     High 100%     High 100%     High 100%
KAND       High  81%     High  84%     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:




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