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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS62 KGSP 170811
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
311 AM EST Sun Nov 17 2019

.SYNOPSIS...
A deep low pressure system will lift away from the Carolina coast
today. A couple of weak cold fronts will move through the area
Monday and Tuesday but temperatures will gradually warm Wednesday
and Thursday ahead of the next cold front expected late in the week.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 230 AM: A coastal low will continue to slowly drift east off
the Carolina coast today, as a shortwave upper ridge builds in ahead
of an approaching deep trough to our west. Moist NELY low-level flow
is maintaining/expanding a stratocu deck, and it may be stubborn to
scatter out due to a fairly strong inversion in the 850-700 mb
layer. The NAM is much more bullish on this cloud cover (and so far
is the closest to reality). So have blended in the NAM and keep a
little more cloud cover today, especially across the south and
eastern zones. This, in combination with ongoing low-level CAA,
should keep max temps below normal today, especially east.
Fortunately, the pressure gradient is relaxing with the departing
low, so it shouldn`t be as breezy as yesterday.

Tonight, a deep H5 trough will enter the OH/TN valleys and pivot
into a negative tilt. This will provide strong mid to upper level
forcing atop the forecast area. The thinking over the last few days
has been for this wave to have little moisture to work with.
Overall, model trends are for a little more moisture and possibly
some light precip being able to break out late tonight. The 00z NAM
looks overdone, but has some support from the SREF and ECMWF.
Meanwhile, the GFS is still dry. So have introduced a slight chc of
light rain across most of the area (best chances will be along and
south of I-85). Even with this trend, I think most people will see a
trace of precip, if anything. Temps were bumped up tonight a
category or so, due to the expected increase in cloud cover (Lows
near to slightly above normal).

&&

.SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
As of 225 AM EST Sunday: The guidance continues to differ with the
strength, location, and resulting precip associated with two short
waves rotating through the longwave trough over the eastern CONUS.
The NAM has trended toward the ECMWF, which has been consistent with
its last three runs, of bringing some light showers across the area
Monday morning. The GFS is dry while the SREF has some precip.
Therefore, have added slight chance PoP to the southern and eastern
sections of the CWFA Monday. Dry conditions return Monday night as
the first short wave moves east. Some of the guidance shows light
precip Tuesday with the second short wave, however they continue to
differ from run to run. Have kept the forecast dry for now until
some consistency develops. Highs will be around 5 degrees below
normal both days, with lows a few degrees below normal.

&&

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
As of 245 AM EST Sunday: Guidance in good agreement early as short
wave ridge moves over on Wednesday keeping a dry forecast in place
and temps near normal.

The guidance is now trending toward better agreement for the rest of
period. Zonal flow develops Thursday as a northern stream short wave
moves into the Upper Midwest. The GFS is trending toward the ECMWF
and not phasing this wave with an upper low over the Four Corners
region. That said, the GFS is still faster than the ECMWF in moving
the northern stream short wave east across the Great Lakes into
Quebec. The GFS is also faster moving the southwestern upper low
into the area by Saturday. The ECMWF shows a similar trend but 12 to
24 hours slower. At the surface, the cold front associated with
these systems moves toward the area Thursday and into the area
Friday. The GFS brings the trailing surface low into the area
Saturday with little break between the initial frontal precip and
precip with the low. The ECMWF shows a break in the precip Friday
night and a slower onset Saturday as the trailing low moves slower.
As usual, went with a model blend due to these differences. This
limits chance PoP to mainly the mountains late Thursday into Friday
and the western CWFA on Saturday. Slight chance PoP is featured
elsewhere.

Temps go above normal Thursday, remain nearly steady Friday, then
drop to a little below normal Saturday.

&&

.AVIATION /08Z SUNDAY THROUGH THURSDAY/...
For KCLT and elsewhere: A coastal low will slowly drift further east
off the Carolina coast today, but lingering low-VFR cigs expected
thru the morning. Guidance is mixed on how much dry air filters in
from the north this aftn, but overall, expect most of the cigs to
scatter out today. An increase in low clouds is expected this
evening ahead of an approaching cold front. Depending on how much
moisture there is to work with, spotty light rain may develop
overnight, but confidence is low. Otherwise, NE winds should remain
gusty thru late morning at KCLT, then become light this aftn and
somewhat variable this evening.

Outlook: Brief low cigs possible early Monday with the passage of a
mainly dry front. The dry high pressure dominate the region for
most of the work week, resulting in VFR conditions.

Confidence Table...

            08-14Z        14-20Z        20-02Z        02-06Z
KCLT       High  98%     High  97%     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  97%     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:

www.weather.gov/gsp/aviation

&&

.GSP WATCHES/WARNINGS/ADVISORIES...
GA...None.
NC...None.
SC...None.

&&

$$
SYNOPSIS...RWH
NEAR TERM...ARK
SHORT TERM...RWH
LONG TERM...RWH
AVIATION...ARK