498 
fxus62 kgsp 290109 
afdgsp 


Area forecast discussion 
National Weather Service Greenville-Spartanburg SC 
909 PM EDT Thursday Aug 28 2008 


Synopsis... 
a weak frontal boundary will slowly approach the forecast area from 
the northwest through the first part of the weekend. On 
Sunday...high pressure will begin to build along the eastern 
Seaboard...then remain in place through the middle of next week. 


&& 


Near term /through Friday/... 
showers and isolated storms diminishing with loss of heating. This 
trend will continue with precipitation ending by midnight. With lots of low 
level moisture remaining over the area tonight...expect areas of fog 
to develop after midnight. Some areas could even see dense fog. 
Continued previous trend and kept lows on the warm side of guidance 
with low clouds and high dew points. On Friday...a weak easterly 
flow should redevelop which will keep the low level moisture in 
place. Forcing is minimal even with the remnant of the upper low 
overhead...but there should be enough instability to allow for 
widely scattered showers...perhaps more near the Blue Ridge. Kept 
high temperature on the cool side of guidance figuring that some of the 
insolation would go toward evaporation of high soil moisture. 


&& 


Short term /Friday night through Sunday/... 
as of 150 PM EDT Thursday...at least isolated convection should 
linger into the evening hours on Friday...as the models indicate 
instability should linger after sunset...and the overall synoptic 
pattern will remain favorable for convection due to a weakness in 
the middle-level ridge. A strong SW trough moving across southeast 
Canada/New England will drive a frontal boundary into the area on 
Saturday. With the lingering weakness in the upper ridge allowing 
for relatively cool middle-level temperatures...and rather high values of 
low-level moisture...respectable instability should develop across 
the area Sat afternoon. At least scattered diurnal convection can be 
expected along the front. We will generally stick to low chance probability of precipitation 
for now...but I wouldn/T be at all surprised if probability of precipitation need to be 
increased in later packages. 


Although the front is expected to be east of the area on Sunday... 
Post-frontal easterly flow will allow for a continued fetch of 
moisture off the Atlantic. This will provide a favorable environment 
for another round of diurnal convection on Sunday...although 
coverage shouldn/T be quite as high as it will be Saturday. 


&& 


Long term /Sunday night through Thursday/... 
as of 215 PM Thursday...overall things look pretty quiet for the 
medium range. The GFS and the European model (ecmwf) are in reasonable agreement for 
the upper pattern over the eastern Continental U.S. With both keeping the area 
under the influence of strong ridge through the end of the forecast 
period. However...they handle the two tropical systems quite 
differently. The European model (ecmwf) take Gustav through the central Gulf Coast 
and wraps it around the large ac centered over the Ohio 
Valley...keeping the effects of Gustav well west of our area. The 
GFS does not allow Gustav to make any northward progress from the 
Gulf Coast instead deflecting it off to the west along the western 
Gulf Coast. With ts Hanna...the GFS fails to depict the storm at all 
while the European model (ecmwf) brings it across the Bahamas and over Cuba by the 
latter part of next week. At any rate...it does not appear at this 
time that either system will have much of an effect on the forecast area 
through Thursday. 


Basically a dry forecast in place through Thursday as the upper ridge 
builds overhead and a surface high dominates the eastern Seaboard. 
Temperatures run close to...if not slightly above climatology norms for early 
September. 


&& 


Aviation /01z Friday through Tuesday/... 
conditions improved rapidly to VFR this afternoon. However...showers 
have developed along the Escarpment with some thunderstorms and rain over the upper 
Savannah River valley. This convection will affect kand early this 
evening. Showers also developing south of kclt along low level 
convergence zone should remain there...but VFR ceilings will continue 
early. Showers should diminish with loss of heating...with VFR 
conditions remaining through early evening. Expect restrictions to 
redevelop across the area late this evening or toward midnight. Low 
level flow has lost much of its upslope component...so fog may be 
the main obstruction instead of low clouds. Still expect IFR to 
develop after midnight over portions of the area. If fog more 
likely...then IFR could be more widespread. With the lack of upslope 
flow and decreasing moisture Friday morning...expect VFR to return more 
quickly than today. Light north to northeast winds tonight will 
increase to around 6 kts Friday morning...then become east to south during 
the afternoon. 


Outlook...early morning fog/stratus is possible the next few days 
which would mean periodic conditions MVFR or worse mainly centered 
around daybreak...with slight to low chance of mainly diurnal 
convection each day through Monday. 


&& 


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


&& 


$$ 
Synopsis...bsh 
near term...PM/rwh 
short term...jdl 
long term...bsh 
aviation...rwh