094 
fxus62 kgsp 040524 
afdgsp 


Area forecast discussion 
National Weather Service Greenville-Spartanburg SC 
124 am EDT Friday Jul 4 2008 


Synopsis... 
the forecast area will remain under the influence of a broad area of 
high pressure through Saturday morning. Then...a weak cold front is 
expected to move slowly across the region Saturday afternoon and 
evening...before becoming stationary Saturday night and dissipating 
on Sunday. The western periphery of subtropical high pressure will 
return across the southeast on Monday...and remain in control 
through the middle of next week. 


&& 


Near term /through today/... 
going forecast is in good shape. Dewpoints are a little higher than 
expected on the southeast fringe of the forecast area...and I/ve accounted for that. 
Otherwise...no changes made. 


Models in good agreement deepening upper trough and increasing 
moisture Friday in continuing S flow. Model soundings show cap eroding 
with convective available potential energy between 500 and 1000 j/kg developing by middle afternoon. Have 
bumped up probability of precipitation late Friday afternoon to solid chance over mountains with slight 
chance across the Piedmont. Expect mild overnight lows as moisture 
increases. Even with increasing cloud cover Friday afternoon...temperatures should 
warm into the low 90s Piedmont...with upper 70s to middle 80s mountains 


&& 


Short term /tonight through Sunday night/... 
as of 140 PM Thursday...the model depict an upper trough amplifying 
over the Great Lakes and Ohio Valley Friday night and Saturday..with 
an upper low closing off over Ohio on Saturday night. This low opens 
up an lift out to the northeast by Sunday night. A cold front will 
move slowly southeast toward the mountains Friday night...with 
increasing moisture suggesting slight chance probability of precipitation in the mountains. 
The NAM is a bit faster than the GFS bringing this feature across 
the mountains ... by Saturday afternoon moisture associated with 
the front will have reached the Piedmont...supporting scattered 
convection. The slowing front weakens while crossing the foothills 
and Piedmont on Saturday night and Sunday...while slowly moving 
southeast...but will still remain a focus for convective activity. 
Temperatures will exhibit a reduced diurnal range under cloud cover. 


&& 


Long term /Monday through Thursday/... 
as of 130 PM Thursday...I generally followed HPC thinking for the 
medium range which closely mirrors the 00z/3 European model (ecmwf). Overall the Monday 
through Thursday period is pretty mundane and features a very typical 
summertime pattern. The dominant feature aloft will be a 595 dm 
subtropical high that gradually weakens by the middle of the week. 
This slight weakness in the ridge may allow more energy to make a 
closer approach towards the latter part of the week...but this is 
like splitting hairs this far out. The European model (ecmwf) features ample low level 
moisture and moderate instability each day so solid chance probability of precipitation seem 
reasonable throughout the period. No significant surface features 
are expected to make it into the region so low level convergence and 
differential heating will serve as the main triggers for diurnal 
convection. As far as temperatures are concerned...I have gone with 
seasonable maximum/min values by blending in the 12z HPC guidance. 


&& 


Aviation /06z Friday through Tuesday/... 
the immediate forecast problem is the visibility at kavl. Temperature/dewpt 
spread is relatively high at 05z and some high cloudiness is moving 
in aloft. For these reasons...the MVFR fog at kavl is kept to a 
tempo group for this issuance. Otherwise...the models agree with 
increasing moisture from the west through the period...but not to 
the point where MVFR conditions develop apart from any deep moist 
convection. Kavl stands the best chance of seeing convective precipitation 
Friday afternoon or evening...but will keep the forecast dry until 
there is overwhelming evidence to the contrary. Tafs are essentially 
VFR through the perios. 


Outlook...moisture will continue to increase Friday night through sun 
with a solid chance of showers/thunderstorms over the weekend...including 
ceiling/visibility restrictions. A diurnal chance of convection will continue 
into middle week. 


&& 


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


&& 


$$ 
Synopsis...bsh 
near term...McAvoy/rb 
short term...jat 
long term...bsh 
aviation...PM