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Area forecast discussion...updated 
National Weather Service Peachtree City Georgia 
520 am EST Sat Nov 21 2009 


Short term /today through Monday/... 
the short term models are in good general agreement on the track of 
the upper low swinging out of Texas. GFS is faster lifting the 
upper low through the Mississippi Valley Sunday...with NAM closer 
to the slower European model (ecmwf). The short wave becomes absorbed in the 
longwave pattern on Sunday while the next system deepens as it 
exits the Pacific northwest...crossing The Rockies on Monday. Both 
the GFS/NAM develop a secondary short wave over the lower Ohio 
Valley early Monday morning while European model (ecmwf) is further north... 
allowing stronger ridging over the southeast on Monday. 


Surface low develops this morning along the East Texas coast...and 
then tracks east...hugging the Gulf Coast through Monday. Again 
NAM/European model (ecmwf) in better agreement with the slower progression of the 
surface low and both depict stronger cold air damming along the 
Appalachians during the day on Sunday. This will keep isolated 
convection generally south of a Columbus to Macon to Augusta line. 
Based upon the latest NAM/European model (ecmwf) solutions light to moderate rain 
will begin late tonight/early Sunday morning and spread north and 
east with heaviest rain during the day on Sunday. GFS/NAM are 
further north when depicting the heaviest rainfall... along a 
Columbus to Athens line while the European model (ecmwf) keeps the heaviest 
rainfall south and east of Macon. NAM/European model (ecmwf) not as impressive with 
rainfall during the day on Sunday...generally in the 1-2" range 
which matches up with the latest HPC quantitative precipitation forecast guidance. Flash flood 
guidance indicate 6 hour totals of 3 to 4.7 inch totals and a 
Flood Watch is not necessary at this time...but there is enough 
uncertainty that I will continue spsffc. 


Guidance temperatures are in fairly good agreement...as high clouds 
start to spread across the area today temperatures will drop from 
middle to upper 60s to lower to middle 60s. Better moisture and clouds on 
Sunday will bring cooler temperatures as most areas will struggle 
into the lower 50s. As wedging begins to erode on Monday 
temperatures will rebound some...mainly across west and central 
portions of the forecast area...where clouds will diminish during 
the day. 




Long term /Monday night through Friday/... 
GFS/European model (ecmwf) continue there differences into the extended periods of 
the forecast. GFS stronger with the developing low over the 
Midwest...but further north the European model (ecmwf). European model (ecmwf) also showing better 
moisture return ahead of the next system Tuesday and Tuesday 
night. Canadian model is in better agreement with the GFS as far 
as the positioning of the upper low...but trends toward the European model (ecmwf) 
surface analysis which keeps the weak wedging and Atlantic 
moisture across the area through Tuesday. The cold front 
approaches the forecast area by Wednesday afternoon and exits the 
forecast area on Thursday with broad high pressure building in 
for Friday. Overall confidence in extended periods are low but will 
blend the models holding onto clouds and low chance probability of precipitation Tuesday 
night and Wednesday. 




&& 


Aviation... 
VFR ceilings today...mid/high clouds associated with low developing 
vicinity of Texas coast. Ceilings lowering below 3 thousand feet after 
00z Sunday and becoming IFR after 06z Sunday. Rain beginning after 
00z and spreading across Georgia during the night as surface low tracks 
east near the Gulf Coast. Some convection possible mainly south of 
Columbus to Macon. Visibility today unrestricted except locally 3 to 
5sm in fog until 14z. Winds northeast increasing to 10 to 15kt after 
14z. 


&& 




Preliminary point temps/pops... 
Athens 64 46 46 43 57 / 5 70 90 60 40 
Atlanta 64 48 49 44 56 / 5 70 80 50 30 
Blairsville 60 43 46 43 54 / 0 50 70 40 40 
Cartersville 63 45 50 44 57 / 5 70 80 30 20 
Columbus 67 52 57 47 57 / 10 100 90 40 20 
Gainesville 63 46 46 44 55 / 5 70 80 40 40 
Macon 65 51 56 46 60 / 5 100 100 70 20 
Rome 64 46 50 45 57 / 5 70 80 30 20 
Peachtree City 64 47 51 45 56 / 5 80 80 60 20 
Vidalia 66 52 58 47 61 / 0 70 100 60 20 


&& 


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


$$ 


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