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Area forecast discussion...updated for aviation 
National Weather Service Peachtree City Georgia 
715 PM EDT Monday Oct 6 2008 


Short term /tonight through Wednesday night/... 
main concern during this period will be a short wave that is 
prognosticated to move across the area Wednesday into Thursday. 
This wave is currently part of a sharp negatively tilted through 
over the central and southern High Plains. All models have this 
longwave trough flattening out tomorrow...but as it does so a 
shortwave will be ejected our direction. Model discrepancies still 
exist...but mainly on timing as the GFS remains the fastest of all 
models. However...12z European model (ecmwf) just coming in is more in line with the 
GFS than the slower NAM. Decided to lean more toward the GFS on 
timing...which starts bringing rainfall into the state Wednesday 
morning. Will likely see a little bit of a delay in onset of 
rain...as strong blocking high over the middle Atlantic coast must 
first be overcome before rainfall can begin. As for thunderstorm 
potential...models still indicating around 500 j/kg of cape and 
around -2 lifted indices Wednesday afternoon...enough to warrant the 
continuation of mentioning thunder in the forecast. However...best 
moisture will stay near the coast as a warm front looks like it will 
be set up near the Florida border Wednesday afternoon...keeping the 
best Gulf moisture out of the area. Also...lapse rates will be 
marginal and 0-6 km bulk shear will only be about 30 kts so severe 
threat looks to be marginal with this system...although it can not 
be ruled out. If the warm front can make it up into central 
Georgia...as GFS is indicating happening late Wednesday night...then 
the severe threat would likely increase. 


As for temperatures...clouds will make for a tricky go of it. Feel 
most of the cloud cover won't start coming in until tomorrow 
morning...so basically went with a forecast slightly warmer than 
persistence...except in the east where it should once again be a 
clear night and therefore cool yet again. After that...extensive 
cloud cover...then rainfall on Wednesday will keep temperatures 
down...so stuck close to the cooler mav...especially Wednesday 
afternoon. 


Long term /Thursday through Monday/... 
weather at beginning of period heavily dependent on evolution of 
shortwave coming through Wednesday. All operational models trying 
to cut this system off from the main flow...with the GFS 
continuing to move it off to the northeast...while the European model (ecmwf) and 
NAM want to let the 500 mb low linger over the southeast into Friday. 
If GFS is correct...then we will be dry from Friday on...while 
European model (ecmwf) would like to hold on to some rain chances...especially over 
the east into the weekend. Into next week...models in good agreement 
with the evolution of the 500 mb pattern...which will become more 
amplified. Both GFS and European model (ecmwf) have the southeastern third of the 
Continental U.S. Centered under a strong subtropical ridge...which would allow 
temperatures to warm up well above normal once again into next week. 
Front that was forecast to push through the area Monday is now 
pegged to do so on Thursday...but given uncertainties that far out 
left the extended forecast from the weekend on out relatively 
unchanged. 


&& 


Aviation... 
moisture increasing to our south and west should be held at Bay as 
low level ridge builds along the East Coast overnight and 
Tuesday...and upper ridge overhead slips gradually to the east. For 
most airports this would likely result in scattered to broken middle 
level clouds in the 8 thousand to 12 thousand foot range. Of 
course...daytime cumulus should form underneath the middle layer 
Tuesday. The exception may be kcsg where low level moisture off the 
Atlantic may be lifted into a ceiling around 3 thousand feet around 
daybreak. Bases would gradually lift during the day Tuesday. As for 
visibility...mixing from a light east wind should prevent anything 
lower than about 4 miles in radiation fog overnight. Some places may 
see no fog at all. 


&& 


Preliminary point temps/pops... 
Athens 54 79 61 67 57 / 0 10 50 80 70 
Atlanta 60 76 64 68 59 / 5 20 70 80 60 
Blairsville 48 73 55 62 56 / 0 10 60 90 70 
Cartersville 53 79 62 67 56 / 0 20 80 80 50 
Columbus 61 75 67 74 60 / 10 40 80 70 30 
Gainesville 55 77 60 64 58 / 0 10 60 90 70 
Macon 58 80 64 75 61 / 5 20 50 70 60 
Rome 53 78 63 68 57 / 0 20 90 80 50 
Peachtree City 54 77 62 69 54 / 5 20 70 80 50 
Vidalia 60 82 64 75 65 / 0 10 20 50 60 


&& 


Ffc watches/warnings/advisories... 
none. 
&& 


$$ 


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