853 
fxus62 kgsp 030240 
afdgsp 


Area forecast discussion 
National Weather Service Greenville-Spartanburg SC 
940 PM EST Tuesday Dec 2 2008 


Synopsis... 
high pressure will shift off the Carolina coast on Wednesday 
allowing a more southerly wind flow and milder temperatures. 
Another cold front will cross our region on Thursday...followed 
by another surface ridge that will build over the southeast 
through next weekend. 


&& 


Near term /through Wednesday/... 
1028 mb high pressure centered over southern Georgia this evening will build 
over the western Carolinas overnight. Deep layer drying will 
continue as winds go light to permit overnight min temperatures 
below most MOS sources. Will continue to feature lows in the teens 
to lower 20s in the mountains...with generally the middle 20s outside of the 
higher terrain. 


The surface high will cover the middle Atlantic and southeast states 
Wednesday with generally clear sky conditions. A sharpening trough aloft 
moving across the plains toward the MS valley during Wednesday will 
result in backing flow aloft and light southwest surface wind behind 
the high centered offshore by 00z Thursday. Sunshine and weak warm 
advection in the light southwest flow will produce temperatures 
generally in the 50s with some 40s in the higher elevations. 


&& 


Short term /Wednesday night through Saturday night/... 
as of 210 PM Tuesday...upper air pattern will continue to transition 
into a large long wave trough over the eastern half of the country 
by the weekend. This means northwest flow aloft will dominate across the southeast 
states and bring a couple cold fronts through the region. The first 
front is still on target to approach the mountains late Wednesday night 
and then move quickly across the forecast area on Thursday. NAM is 
trending slower with this front than the GFS. The faster GFS 
solution is supported by the Gem and and sref...so will continue 
with the idea of increasing probability of precipitation over the mountains after 06z Thursday. 
Moisture transport from the Gulf never arrives so with limited 
moisture to work with precipitation amounts will be on the light side. Any 
rainfall outside of the mountains expected to be in the trace to a 
few hundredths range. Precipitation is expected to be all liquid as warming 
aloft occurs. The only fly in the ointment is that some Mountain 
Valley locations could have sub-freezing temperatures at the onset of 
precipitation early Thursday. Therefore...have included a mention of freezing 
rain (zr)in those locations. However...any freezing rain will be brief with no 
real problems anticipated. A brief period of flurries may also occur 
above about 3500ft behind the front on Thursday afternoon as temperatures aloft 
cool. 


By Thursday evening the front is expected to be out of the area with 
clearing conditions. High pressure will build in behind the front 
and produce generally clear and cool conditions Friday and Sat. GFS 
model time height does show some middle/high clouds traversing the area 
Friday night into Sat...so will show some increase in clouds then. 
Another cold front will move through the area Sat night with little 
fanfare. The only precipitation may be a brief period of upslope snow 
showers Sat night in favored mountain areas. With this upper air 
pattern...temperatures will continue to be on the cool side of seasonal 
averages by a couple categories. 


&& 


Long term /Sunday through Tuesday/... 
as of 2 PM Tuesday...HPC preferred the more progressive GFS 
today...which received the most support form ensemble forecasts. 
This solution has an upper trough over the East Coast on 
Sunday...followed by an upper ridge on Monday...and another 
transient trough on Tuesday. Our are starts out Sunday in a tight 
pressure gradient behind a departing cold front...with a northwest 
flow now event ongoing along the NC border with Tennessee. This event winds 
Don Sunday afternoon. A dry surface ridge then crosses the area on 
Sunday night and Monday. Moisture on the back side of this ridge 
spreads east across the area Monday night...as a warm front 
approaches from the Gulf states. Model soundings are not very 
supportive of precipitation until Tuesday morning...at which point 
they would indicate snow in the north...freezing rain or rain in the 
south...and sleet in between...becoming all rain by midday. 
Temperatures will be more like middle January than early December... 
except in the Lee of the mounains on sudnay...where downslope 
warming will bring maximums close to normal. 


&& 


Aviation /03z Wednesday through Sunday/... 
surface high pressure will build northeast from the deep south 
across the terminal forecast area overnight. This will keep profiles 
dry and winds light...with VFR conditions expected throughout. A 
light southerly return flow will develop on Wednesday as the high 
pressure center moves offshore. 


Outlook...a cold front is expected to move across the area on 
Thursday...with a chance of showers and ceiling and visibility 
restrictions...especially at kavl. Dry conditions are anticipated 
Friday. A fast moving cold front is forecast to move through the 
area late Saturday. 


&& 


Gsp watches/warnings/advisories... 
Georgia...none. 
NC...none. 
SC...none. 


&& 


$$ 
Synopsis...deo 
near term...hg 
short term...lg 
long term...jat 
aviation...hg