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fxus62 kgsp 030723 
afdgsp 


Area forecast discussion 
National Weather Service Greenville-Spartanburg SC 
223 am EST Wednesday Dec 3 2008 


Synopsis... 
high pressure located over the southeast will shift over the 
Carolinas coast today in advance of an approaching cold front. The 
front will move east of the forecast area by Friday morning...and 
high pressure will return to the eastern Seaboard by early next week. 


&& 


Near term /through tonight/... 
500 mb ridge will track across the region today. Surface high center will 
move east of area...putting County Warning Area in warmer SW flow. Add clear skies to 
the mix and hi temperatures should warm close to average this afternoon. Upper ridge 
moves east tonight while a shortwave approaches from the west. Moisture 
from the Gulf is expected to surge up toward the Tennessee Valley ahead of 
this system and approach the mountains by daybreak. Both GFS and NAM were 
slower than previous model runs so backed off probability of precipitation for the late 
overnight period...keeping a low chance in the far West Mountains and along 
the Tennessee border...tapering to slight chance just southeast of there. With 
increasing clouds overnight radiational cooling will be minimal and 
temperatures should be in the low to middle 30s...above freezing across the 
County Warning Area. Model soundings show a significant warm nose aloft as well so 
p-type is not expected to be an issue at this time. 


&& 


Short term /Thursday through Saturday/... 
as of 130 am Wednesday...there is still uncertainty in timing of 
frontal passage Thursday...as models have changed from continuity (and are in 
greater disagreement with each other). The 00z GFS has more support 
from ensembles and other models than the 00z NAM (hence the NAM was 
not used in this forecast package). When looking at the 00z GFS...it is 
hard to imagine there being more than a few showers with the frontal passage 
(especially outside the mtns). Most of the upper level energy remains 
north of the area...and moisture will be quite limited. If 
anything...overall pop have been pared back just a tad for Thursday. 
Maximum temperatures were bumped up (esp east of the mtns) per the new GFS due 
to a slightly later frontal passage. The 800 mb fnt is shown to remain north of 
the area through Thursday night. There will be lingering cloud 
cover...but pop was kept at only slight chance. 


Friday and Saturday....fntl boundary at the surface is expeceted to sag south 
and east of the forecast area. However...at 850 mb the fnt is shown to stall in vicinity of 
our County Warning Area b4 washing out as hi pressure builds across the Ohio Valley. Moisture will 
be shallow and lift will be weak along the boundary. So I increased cloud 
cover...but did not introduce any pop for Friday. Maximum temperatures will be 
slightly below normal under low level cold air advection and low-middle clouds. Another 
reinforcing short wave rounds the base of the l/west eastern Continental U.S. Trough and 
approaches the forecast area Saturday...with only some middle-upper level moisture. So 
no precipitation expeceted Saturday. 


&& 


Long term /Saturday night through Tuesday/... 
as of 2 am Wednesday...a reinforcing shortwave trough dives towards 
the southern Apps Saturday night...and pushes east of the forecast area on 
Sunday. Low level winds dont veer around to northwesterly until 06z 
Sunday and a relatively short lived upslope northwest flow event ensues. 
There should be sufficient low level moisture and with 850 mb temperatures 
falling to around -9c...expect decent coverage of snow showers along 
the Tennessee line Sunday morning. The event will be rather short lived as 
high pressure quickly builds in from the northwest on Sunday and low level 
moisture retreats to the NE. Nearly zonal flow aloft and high 
pressure at the surface set up a quiet day for Monday. The next 
system comes in the form of a sharp and vigorous upper level trough 
which approaches the region Monday night and Tuesday. The high that 
moves in on Monday briefly appears to set up some cad along the 
eastern Seaboard through early Tuesday...but appears to be quite 
transient and moves quickly off the East Coast on Tuesday. A cold 
front is expected to move across the forecast area on Tuesday and the onset of 
precipitation could be interesting concerning ptype across the NC mnts and 
foothills early Tuesday. However...limiting factor will be the dry 
sub cloud layer which should greatly limit precipitation reaching the 
ground while temperatures are still close to freezing. Will be Worth 
keeping an eye on though. Overall...forecast temperatures for the period 
run 3 to 5 degrees below normal. 


&& 


Aviation /08z Wednesday through Sunday/... 
upper ridge and surface high continue to build over the area. Look for 
clear skies with light winds overnight...then S to SW winds 8-10kt 
during the day. 


Outlook...cold front will move across the area Thursday with a chance of 
showers and ceiling/visibility restrictions...especially at kavl. Dry 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...bsh 
near term...rb 
short term...Arkansas 
long term...bsh 
aviation...rb