Area forecast discussion...updated 
National Weather Service Peachtree City Georgia 
735 am EDT Tuesday may 21 2013 


Short term /today through Wednesday/... 
upper ridge continues building over the southeast today with an 
upper low near southeast Georgia/northeast Florida. The air mass remains 
unstable however water vapor shows some drier air has worked into 
northwest Georgia. Have kept a slight chance/low chance probability of precipitation mainly over 
the eastern half of the County Warning Area this afternoon and evening...closer to 
the upper low and better moisture. Tonight looks like a lull between 
systems and have only included slight chance probability of precipitation across the extreme 
north. The GFS hints at a short wave crossing the Tennessee Valley 
overnight. A closed upper low moving into the Great Lakes region by 
Wednesday should push a front into the lower Mississippi Valley 
toward Georgia. The models want to keep the front west of the County Warning Area 
during the day...but an increase in moisture and instability should 
support better chances of thunderstorms across the County Warning Area by Wednesday 
afternoon. Mav/met temperatures are close and have taken a 
compromise. 


41 


Long term /Wednesday night through Monday/... 
weak cold front approaching with an upper level trough/short wave 
forecast to move into the area Wednesday night and with associated 
moisture and instability...scattered showers and thunderstorms 
are reasonable...most so for the evening hours. The weak cold 
front moves into the area on Thursday. It is unclear how much 
convection will be associated with the front. The best instability 
is forecast over central Georgia with the best upper support over north Georgia. 
At this time it seems reasonable that there will be a chance of 
showers and thunderstorms...most so in the afternoon. The main 
upper trough moves east for Friday with a drier airmass moving over 
the area behind the front as surface high pressure builds along 
with a much drier northwest flow. Dry conditions continue Saturday as 
high pressure moves across the eastern states. Sunday looks to be 
mainly dry as well except the northwest flow aloft begins to become more 
active to the north with some moisture skirting by the area. Moisture 
continues to skirt by Monday and Tuesday with a sharp gradient of 
significant moisture at the Georgia/SC line. For now will leave a dry 
forecast for Monday/Tuesday and continue to monitor the progress 
of the northwest flow. Temperatures generally running within 5 degrees of 
normal through the period except Saturday and Sunday morning lows 
running 5-10 degrees below normal. 


Bdl 


&& 


Aviation... 
12z update... 
expecting VFR today with scattered to broken clouds at or above 040. IFR 
visibilities will improve quickly this morning as most areas of fog 
are shallow. Widely scattered convection possible this afternoon and 
evening. Probability of having a thunderstorm affect the taf sites 
is low so have left thunder out of forecast for now. Winds expected 
to become southwest later this morning around 5 to 8kt. Winds will 
gradually Switch Back around to the south-southeast again by 00z this evening 
but will be generally less than 5kt. . 


//atl confidence...12z update... 
medium confidence on timing of SW winds. High confidence on all 
other elements. 


41 


&& 


Preliminary point temps/pops... 
Athens 87 64 86 64 / 30 30 40 40 
Atlanta 86 67 84 66 / 10 10 50 40 
Blairsville 82 60 81 60 / 30 30 50 50 
Cartersville 86 64 85 63 / 10 10 50 40 
Columbus 90 68 88 68 / 10 10 30 30 
Gainesville 85 66 84 64 / 30 30 50 40 
Macon 89 64 88 65 / 20 20 30 30 
Rome 86 63 85 62 / 10 20 50 40 
Peachtree City 87 61 86 63 / 10 10 50 30 
Vidalia 88 69 88 68 / 30 30 30 30 


&& 


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


$$ 


Short term...41 
long term....bdl 
aviation...41