Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 070238
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
938 PM EST Fri Dec 6 2019

.SYNOPSIS...
Dry high pressure returns for the weekend, but an unsettled weather
pattern will develop by early Monday, with rainy conditions expected
through Tuesday ahead of an approaching cold front. Dry high
pressure expected for later next week.

&&

.NEAR TERM /THROUGH SATURDAY/...
As of 940 pm: Quiet weather continues with only minor adjustments
made to cloud cover.

As of 715 pm: The drying trend behind the weak system has started as
sinking air from aloft has already diminished much of the higher
cloud deck. Have trended towards faster clearing as indicated by
model guidance and makes sense given the expected downslope
northerly flow. Have also tweaked temperatures down somewhat
especially for late tonight.

Otherwise, once the wave is past this evening, the flow aloft will
return to WNW and dry, allowing high pressure at the sfc to build in
overnight. Clouds are expected to thin/scatter out toward daybreak
Saturday, but not soon enough, so min temps were kept above normal.
Once the high center makes it east of the Appalachian spine on
Saturday, it should be in the proper position to support a dry cold
air damming wedge Saturday afternoon, altho it will only be marked
with a stratocu cloud deck expanding across the NC foothills and wrn
Piedmont, trapped under a subsidence inversion. The development of
the wedge and its potential for clouds will modulate the high temps
in the afternoon, with the nrn foothills and NW Piedmont likely
remaining below normal, but the wrn Upstate and northeast Georgia
climbing above normal.

&&

.SHORT TERM /SATURDAY NIGHT THROUGH MONDAY/...
As of 115 PM Fri: A short wave ridge crosses the area Sunday with
southwesterly flow developing Monday as a northern stream short wave
moves into the Great Lakes and a southern stream wave moves to the
AX/NM line. This allows other short wave energy to move through the
flow and across the area. At the surface, cold high pressure noses
down into the area from the NE. This high migrates eastward Monday
and the air mass modifies. The surface flow weakens as a result of
this limiting the potential of an in-situ CAD even as precip
develops in the moist southerly low level flow ahead of the short
waves and frontal system off moving into the OH and lower MS
valleys. Precip chances to increase from west to east across the
area Sunday night and Monday morning before tapering off back toward
the mountains for the afternoon as the already weak isentropic lift
weakens over the Piedmont areas but upslope flow remains into the
mountains. QPF will be light outside of the mountains as well
helping to limit CAD initiation. Although Sunday night lows will be
cold across portions of the mountains, low level WAA takes place in
the southerly flow warming temps to above freezing overnight. This
should help keep precip all liquid as it develops overnight. Lows
will be a couple of degrees above normal Saturday night then 5 to 10
degrees above normal Sunday night. Highs Sunday will be around 5
degrees below normal then rise to up to 5 degrees above normal
Monday.

&&

.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
As of 230 PM Fri: Short waves from the short term will phase
somewhat as they move east during the first part of the long term.
These waves will push the cold front to our west into the area on
Tuesday then east of the area Wednesday. This means likely precip
chances Monday night through Tuesday evening with diminishing
chances late Tuesday night and ending Wednesday. Cannot rule out
some weak instability Tuesday afternoon and evening. Of course,
shear will be quite strong, so this situation will need to be
monitored for possible isolated severe storms. Isolated heavy
rainfall will also be possible. Temps ahead of the front will be
above normal. As cold air rushes in behind the front, some of the
rain may change to snow across the mountains. Right now, this looks
like a short lived NW flow event, so advisory level accums look
unlikely.

Dry continental high will spread across the Southeast in the wake of
the front. Max temps will fall back below normal Wed and Thu within
this airmass. Guidance continues to feature the potential for a
Miller A type low pressure system moving east along the Gulf Coast
by Friday. The latest GFS and ECMWF have slowed this system down as
northern and southern stream waves phase over the Midwest and go
negative tilt. This is slowing the development and movement of the
surface low as well. Have introduced late day chance PoP on Friday
as some precip may be moving in from the south by then. The
atmosphere modifies and with the late precip onset, any precip late
Friday should be rain. There is still low confidence in this part of
the forecast as it continues to change from run to run, so as usual,
continue to monitor the forecast for the latest updates.

&&

.AVIATION /03Z SATURDAY THROUGH WEDNESDAY/...
At KCLT and elsewhere: A developing wedge will support NE/E winds by
15Z for most, especially east of the mountains with low VFR/ high
MVFR cigs likely at times for foothill locations, possibly including
KHKY. BKN cigs also possible at times for KAVL after 15Z. Low
confidence in wind direction for KAVL after 13Z.

Outlook: Flight restrictions are likely to return sometime late
Sunday into early Monday with rain at times until a cold front
pushes through the area Tuesday.

Confidence Table...

            02-08Z        08-14Z        14-20Z        20-00Z
KCLT       High 100%     High 100%     High 100%     Low   57%
KGSP       High 100%     High 100%     High 100%     High  89%
KAVL       High 100%     High 100%     High 100%     High  91%
KHKY       High 100%     High 100%     High  89%     Low   57%
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...65/PM
SHORT TERM...RWH
LONG TERM...RWH
AVIATION...65


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