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Area forecast discussion...updated aviation 
National Weather Service Peachtree City Georgia 
535 am EDT sun Mar 21 2010 


Short term /today through Tuesday/... 
deep upper low over the arklatex will move east over Arkansas... 
Louisiana...and Mississippi today crossing Alabama overnight 
tonight and reaching the southern Appalachians along the Tennessee and 
Georgia state line Monday morning. Radar imagery early this morning 
showed widespread rain showers with some embedded convective 
elements tracking northeastward with across MS/southern and central Alabama and 
the Florida Panhandle with lightning remaining out over the Gulf of 
Mexico thus far. While initial echoes are primarily virga...rain 
should start reaching the ground in vicinity of Columbus shortly around 
sunrise. Dynamics continue to look impressive with this 
approaching system...with diffluent 110kt h2 jet streak and 
several significant shortwaves rotating around the upper low. Low 
level thermal advection/isentropic ascent maximized between 15 and 
21z today as 65 knots low level jet noses up into central Georgia ahead of cold 
front. Frontal passage expected this afternoon over western Georgia into the Savannah 
River valley by evening. Extent of Gulf moisture return and 
instability however are lacking...with precipitable waters not getting above 1 
inch and convective available potential energy expected to remain less than 200 j/kg. The strong 
dynamic ascent should help overcome that limited cape to allow for 
a few thunderstorms this afternoon...though probably not enough 
to lead to much severe risk aside from some gusty winds in the 
deeper convective cells. If more instability could be 
realized...strongly sheared environment could result in some 
rotating rain showers/thunderstorms and rain that would need to be watched closely. 


Dry slot works into the area briefly behind the front 
this evening...though clouds and showers will move back in early 
Monday morning as upper low nears north Georgia from the west. Low 
level cold pool associated with the upper low is pretty 
respectable for this time of year with 800 mb temperatures around -5c over 
north Georgia on Monday. Thermal profiles support snow above ~2500 feet 
elevation with light accumulations possible in those few Georgia 
Mountain locations above 3000 feet. Elsewhere in the mountains may 
see a mix of rain/snow at times...but lower valleys will remain 
almost entirely rain/drizzle. 


The upper low moves off into the Middle-Atlantic States early Tuesday 
with any lingering showers/sprinkles ending quickly Tuesday 
morning as an upper level ridge and a warmer surface high build 
into the local area from the west. 


Long term /Tuesday night through Saturday/... 
that high remains the dominant influence Tuesday night into 
Thursday...before a weaker middle/upper level shortwave crosses our 
area from the west Thursday night and Friday. Global models are in 
reasonably good agreement through that time with a weak high 
briefly building in for Saturday. 


Rrh 


Aviation /8 am Sunday through 8 am Monday/... 
radars indicate areas of light rain from middle clouds in southwest Georgia 
moving north at 30 kts at this time. Expect ceilings to gradually 
lower to MVFR as the Gulf moisture modifies the airmass over Georgia in 
advance of the low pressure system in Arkansas and cold front in MS. Will 
maintain current forecast rationale of widespread showers developing 
this morning with a few thunderstorms this afternoon and early 
evening with the greatest instability just before and after frontal 
passage. Breezy surface winds most of the day due to the approaching 
low pressure system. 


&& 


Preliminary point temps/pops... 
Athens 64 40 51 36 65 / 80 70 40 20 5 
Atlanta 61 38 48 38 63 / 80 40 40 10 0 
Blairsville 58 36 44 33 56 / 100 80 40 30 10 
Cartersville 61 37 46 36 62 / 80 40 50 20 5 
Columbus 63 38 53 40 67 / 80 30 30 10 0 
Gainesville 62 40 48 37 62 / 100 70 40 20 10 
Macon 66 41 56 38 69 / 80 40 20 10 0 
Rome 61 40 48 41 64 / 100 40 50 20 5 
Peachtree City 62 37 49 35 64 / 80 30 40 10 0 
Vidalia 68 46 62 43 68 / 80 50 20 10 0 


&& 


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


$$