962  
FXUS62 KFFC 280534  
AFDFFC  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE PEACHTREE CITY GA  
134 AM EDT TUE APR 28 2015  
 
   
PREV DISCUSSION
 
/ISSUED 757 PM EDT MON APR 27 2015/  
 
EVENING UPDATE...  
CURRENT FORECAST LOOKS ON TRACK WITH HIGH CLOUDINESS ON TAP FOR  
TONIGHT. THE THICKER HIGH CLOUDS ARE EXPECTED ACROSS CENTRAL GA  
WHERE THE PROJECTED OVERNIGHT LOWS ARE THE WARMEST AND STILL LOOK  
REASONABLE. THE THINNER HIGH CLOUDS ACROSS THE NORTH SHOULD ALLOW  
THE COOLER PROJECTED LOWS THERE BE REALIZED... BUT WILL MONITOR  
THE CLOUDS AND THEIR INFLUENCE ON OVERNIGHT TEMPS CLOSE. /39  
 
SHORT TERM /TONIGHT THROUGH TUESDAY NIGHT/...  
/ISSUED AT 313 PM EDT MON APR 27 2015/  
LATEST REGIONAL SURFACE ANALYSIS SHOWS SEVERAL BOUNDARIES OF NOTE  
WITH THE MAIN BEING THE OLD FRONTAL BOUNDARY ANALYZED FROM THE  
GULF COAST THROUGH CENTRAL FLORIDA. DEWPOINT BOUNDARY HOWEVER IS  
CONSIDERABLY FURTHER NORTH INDICATED BY A SUBTLE TROUGH AND  
ROUGHLY ALONG AND SOUTH OF A CSG TO MCN LINE. DEWPOINTS IN THE 30S  
CURRENTLY FOR NORTH GEORGIA AND IN THE MID 50S SOUTH OF THIS  
FEATURE.  
 
FOR TONIGHT...LOW PRESSURE WILL BEGIN TO DEVELOP ALONG THIS FRONT  
OVER THE NORTHERN GULF OF MEXICO AS CLOSED UPPER LOW MOVES SLOWLY  
EAST OUT OF TEXAS. THIS WILL ALLOW FOR AND ISENTROPIC UPGLIDE  
SETUP TO DEVELOP LOCALLY WITH INCREASED MID LEVEL CLOUDS INITIALLY  
DECREASING TO SOME LOWER CIGS FOR THE SOUTHWEST PORTIONS OF THE  
FORECAST AREA LATE TONIGHT. THIS WILL CORRESPOND TO AN INCREASE IN  
LIGHT RAIN DEVELOPMENT FOR THESE SAME AREAS AND WILL KEEP CHANCE  
POPS IN THROUGH TUESDAY MORNING.  
 
DEVELOPING DIFFLUENT FLOW ALOFT WILL ACT IN TANDEM WITH  
STRENGTHENING ISENTROPIC ASCENT TO INCREASE RAIN CHANCES RAPIDLY  
LATE TUESDAY AFTERNOON THROUGH THE EVENING HOURS. HAVE RAMPED UP  
POPS EVEN FURTHER AND NOW HAVE A SMALL AREA OF CATEGORICAL FOR  
WEST CENTRAL GEORGIA PORTIONS LATE TUESDAY. INSTABILITY WILL BE  
LIMITED BUT NAM12 DOES INDICATE MARGINAL VALUES ENCROACHING UPON  
THE FAR SOUTHERN SECTIONS AND WILL GO WITH ISOLATED THUNDER  
THROUGH THE REMAINDER OF THE SHORT TERM PERIOD.  
 
AS UPPER LOW TRACKS ACROSS NORTHERN ALABAMA...DYNAMICS ARE PRETTY  
MUCH MAXIMIZED FOR THIS EVENT TUESDAY NIGHT AND HAVE GONE  
CATEGORICAL FOR ALL AREAS WITH ISOLATED THUNDER FOR THE SAME AREAS  
MENTIONED BEFORE.  
 
DEESE  
 
LONG TERM /WEDNESDAY THROUGH MONDAY/...  
/ISSUED AT 313 PM EDT MON APR 27 2015/  
MADE A FEW ADJUSTMENTS TO THE EXTENDED FORECAST GRIDS...MAINLY IN THE  
FIRST FEW PERIODS. ADJUSTED POPS A BIT AND ALSO ADJUSTED AREA FOR  
THUNDER WEDNESDAY TO MATCH LATEST MODEL TRENDS. ADDED THUNDER TO THE  
THURSDAY/THURSDAY EVENING PERIOD AS WELL. INSTABILITY IS FORECAST TO  
BE MARGINAL...HOWEVER STEEP LAPSE RATES INDICATE SHALLOW CONVECTION  
IS LIKELY TO CONTAIN FAIRLY VIGOROUS UPDRAFT POTENTIAL. OTHERWISE  
MINIMAL CHANGES MADE TO THE REMAINDER OF THE EXTENDED FORECAST  
PERIOD. PLEASE SEE THE PREVIOUS EXTENDED FORECAST DISCUSSION BELOW.  
 
20  
 
PREVIOUS LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...  
 
STILL ONE MAIN SYSTEM TO FOCUS ON FOR THE LONG TERM. CLOSED UPPER  
LEVEL LOW SLIDES FROM THE MISSISSIPPI VALLEY INTO THE TENNESSEE  
VALLEY TUESDAY NIGHT WHILE THE SFC LOW SLIDES ALONG THE GULF COAST.  
THIS SHOULD RESULT IN RAIN SPREADING ACROSS THE CWA AT THE BEGINNING  
OF THE LONG TERM AND TUESDAY NIGHT AND WEDNESDAY STILL LOOK TO BE THE  
MOST LIKELY TIME PERIOD FOR PRECIPITATION. AS THE SFC LOW TRACKS INTO  
THE ATLANTIC...RAIN SHOULD END BY FRIDAY. THERE STILL REMAIN SOME  
DIFFERENCES IN HOW THE ECMWF AND THE GFS ARE RESOLVING FEATURES WITH  
THIS SYSTEM /ESPECIALLY IN TERMS OF THE SFC LOW TRACK ONCE IT MOVES  
INTO THAT ATLANTIC AND THE UPPER LEVEL SHORTWAVE AS IT TRACKS ACROSS  
THE EAST/ BUT THE MAJORITY OF THE TIME THE TWO MODELS ARE IN DECENT  
AGREEMENT ON THE WEATHER IMPACTS FOR THE CWA. INSTABILITY VALUES ARE  
A LITTLE BIT HIGHER THAN HAVE BEEN NOTED IN PREVIOUS RUNS WITH MUCAPE  
VALUES EXCEEDING 1000 J/KG ON WEDNESDAY AFTERNOON. IN ADDITION...THE  
HIGHER VALUES SPREAD FURTHER NORTHWARD. WITH THIS FORECAST HAVE  
INCLUDED THAN MENTION OF THUNDERSTORMS FURTHER NORTHWARD /INTO THE  
SOUTHERN AND WESTERN PORTIONS OF THE ATL METRO AREA/ COMPARED TO THE  
PREVIOUS FORECAST.  
 
HIGH PRESSURE BUILDS IN FOR THE WEEKEND...ALLOWING FOR DRY  
CONDITIONS ACROSS THE CWA.  
 
11  
 

 
   
AVIATION
 
 
06Z UPDATE...  
VFR CONDITIONS STILL EXPECTED THROUGH 00Z TUESDAY. AFTER 00Z  
TUESDAY...CIGS DROP TO MVFR AND PRECIP SHOULD BEGIN TO APPROACH  
THE NORTHERN TERMINAL SITES. VSBYS AND CIGS MAY BEGIN TO DIP TO  
IFR VALUES AFTER 06Z TUESDAY. CONFIDENCE IS RATHER LOW AT THAT  
POINT...SO ONLY INCLUDED IT IN A PROB GROUP. WINDS WILL REMAIN  
EASTERLY TODAY.  
 
//ATL CONFIDENCE...06Z UPDATE...  
MEDIUM CONFIDENCE ON CIGS AFTER 06Z TUESDAY. OTHERWISE...HIGH  
CONFIDENCE ALL ELEMENTS.  
 

 
   
PRELIMINARY POINT TEMPS/POPS
 
 
ATHENS 68 51 60 50 / 60 80 80 30  
ATLANTA 67 52 60 50 / 70 80 70 20  
BLAIRSVILLE 65 47 57 44 / 50 80 80 30  
CARTERSVILLE 68 51 60 48 / 70 80 80 20  
COLUMBUS 70 57 66 51 / 80 80 60 20  
GAINESVILLE 66 50 57 49 / 60 80 80 30  
MACON 69 54 65 49 / 70 80 70 20  
ROME 69 52 62 49 / 70 80 80 20  
PEACHTREE CITY 68 52 62 48 / 70 80 70 20  
VIDALIA 71 60 71 56 / 70 80 80 30  
 

 
   
FFC WATCHES/WARNINGS/ADVISORIES
 
 
NONE.  

 
 

 
 
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