HAMweather.com Area Forecast Discussion for County Warning Area FFC

Thu, 16 Feb 2012 11:52:00 GMT
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE PEACHTREE CITY GA
645 AM EST THU FEB 16 2012

.UPDATE...
PRECIP CONTINUES TO MOVE EAST RAPIDLY AND ACCORDING TO THE LATEST 
RUC THE BULK OF THE PRECIP HAS EXITED NORTHWEST GA. A FEW SHOWERS 
CONTINUE OVER NORTH AL AND THESE COULD PUSH INTO NORTHWEST GA OVER 
THE NEXT 1 OR 2 HOURS. WILL THEREFORE LOWER POPS TO CHANCE OVER 
NORTHWEST GA FOR THIS MORNING. NO OTHER CHANGES PLANNED.

17

.PREV DISCUSSION...
/ISSUED AT 234 AM EST THU FEB 16 2012/

SHORT TERM /TODAY THROUGH FRIDAY NIGHT/...
ALL MODELS IN GOOD AGREEMENT BY PUSHING THE PRECIP OUT OF NORTH GA 
BY 18Z AND OUT OF THE CWA BY 00Z AND THEN KEEPING THE CWA DRY 
THROUGH FRIDAY. THE SURFACE COLD FRONT WILL BE MORE LIKE A SURFACE 
TROUGH AS THERE WILL NOT BE A DROP IN TEMPS WITH JUST A SLIGHT DROP 
IN DEW POINTS. INSTABILITY WILL BE LACKING THIS MORNING AS THE BAND 
OF PRECIP MOVES ACROSS NORTH GA...HOWEVER AS THE PRECIP MOVES 
INTO CENTRAL GA INSTABILITY INCREASES A LITTLE...JUST ENOUGH TO 
ALLOW FOR SOME THUNDER. WILL THEREFORE REMOVE THUNDER FROM THE 
NORTHERN ZONES AND GO WITH A SLIGHT CHANCE OF THUNDER FOR CENTRAL 
GEORGIA THIS AFTERNOON. ALTHOUGH THE MID AND LOWER LEVELS DRY OUT 
TONIGHT AND FRIDAY...THERE APPEARS TO BE PLENTY OF HIGH LEVEL 
MOISTURE WHICH SHOULD BE ENOUGH TO WARRANT MOSTLY CLOUDY SKIES 
TONIGHT AND FRIDAY. THIS WILL DEFINITELY PLAY A ROLE IN LOW TEMPS 
TONIGHT...AND WITH THE ALREADY COLD BIAS OF THE MODELS...WILL RAISE 
MOS TEMPS A FEW DEGREES FOR TONIGHT. A EAST TO NORTHEAST SURFACE 
FLOW...CLOUDS AND LOWER LOW LEVEL THICKNESSES ON FRIDAY INDICATE 
TEMPS WILL BE AT OR JUST SLIGHTLY COOLER ON FRIDAY. 

MODELS DIVERGE ON THE SOLUTION FOR FRIDAY NIGHT WITH THE GFS BEING 
THE DRIEST AND THE NAM/ECMWF BEING THE WETTEST. NOT A LOT OF 
CONFIDENCE IN EITHER OF THE MODELS AT THIS POINT ALTHOUGH ALL MODELS 
ARE FORECASTING PRECIP ACROSS CENTRAL GA AND WILL LIMIT POPS TO THAT 
AREA FRIDAY NIGHT. 

LONG TERM /SATURDAY THROUGH WEDNESDAY/...
LARGE DIFFERENCES...MAINLY WITH TIMING...BETWEEN THE GFS AND ECMWF 
THROUGHOUT THE LONG TERM. HOWEVER...THE LATEST ECMWF IS COMING IN 
LINE WITH THE GFS ON THE SATURDAY SYSTEM...WHICH IS A PRETTY DYNAMIC 
SYSTEM...ALTHOUGH THE ECMWF IS A LITTLE SLOWER. WHAT THEY BOTH AGREE 
ON IS THAT PRECIP WILL FALL AND THEREFORE HIGH POPS LOOK REASONABLE 
FOR SATURDAY INTO SATURDAY NIGHT. WHAT THEY ALSO AGREE ON IS A WEDGE 
ACROSS NORTH GEORGIA KEEPING THE THUNDERSTORM THREAT CONFINED TO 
CENTRAL GA. ON SUNDAY THE ECMWF BRINGS WRAP AROUND MOISTURE ACROSS 
THE NORTHERN PART OF THE CWA WHILE THE GFS IS DRY. AT THIS 
POINT WILL GO WITH A COMPROMISE OF THE TWO AND KEEP LOW POPS ACROSS 
THE NORTH SUNDAY. A SHORT-LIVED H5 RIDGE BUILDS OVER THE EASTERN 
U.S. MONDAY AND TUESDAY KEEPING THE CWA DRY...AND THE NEXT SYSTEM 
DEVELOPS OVER THE SOUTHERN PLAINS. AGAIN TIMING DIFFERENCES APPEAR 
WITH THE ECMWF ABOUT 6 TO 12 HOURS FASTER THAN THE GFS AND WILL GO 
WITH A COMPROMISE ON THE POPS.

17

.AVIATION...
12Z UPDATE...
MAIN RAIN AREA ASSOCIATED WITH FAST MOVING UPPER TROUGH IN ZONAL 
FLOW HAS EXITED THE AREA. PCPN FROM THIS POINT FORWARD EXPECTED ONLY 
TO BE -DZ. TSRA THREAT COMPLETELY OVER THIS TAF VALID PERIOD. MAIN 
TROUGH LINGERS BACK...LEAVING VERY MOIST LOW-LEVEL AIR MASS AND 
CHAOTIC WIND FIELD. EXPECT IFR-LIFR CIGS AND IFR VSBYS THROUGH AT 
LEAST MID-DAY WITH LITTLE IMPROVEMENT EXPECTED UNTIL AT LEAST 
MID-AFTERNOON. SITUATION BECOMES INCREASINGLY UNCLEAR 
OVERNIGHT...BUT THINKING NOW IS THAT LOW-LEVEL/BL AIR MASS WILL 
REMAIN DECOUPLED AND CONTINUE TO PROMOTE OR CONTINUE IFR-LMVFR CIGS. 
VSBYS SHOULD GRADUALLY IMPROVE TO MVFR THROUGH THE AFTERNOON/EARLY 
EVENING...THEN TREND BACK TO IFR/LIFR IN BR/FG AFT 06Z. MODELS NOT 
ADVERTISING THIS...BUT SYNOPTIC PATTERN ALMOST IDENTICAL TO 
YESTERDAY...WITH DENSE AND WIDESPREAD RADIATIONAL FOG A GOOD 
POSSIBILITY. WINDS REMAIN VERY CHAOTIC AND CONTAMINATED BY PASSING 
SHRA ACTIVITY. WINDS JUST ABOVE THE SFC ARE SSW 5-10KTS. EXPECT 
WINDS TO SLOWLY VEER TO SSW-SW BY MID-DAY...BUT DECOUPLED LOW-LEVEL 
AIR MASS MAY SLOW THIS MORE THAN CURRENTLY ANTICIPATED. WINDS 
EXPECTED TO SHIFT TO NW TOWARD EVENING AS MAIN UPPER TROUGH PASSES 
BY...THEN VEER TO NE NEAR/SHORTLY AFTER 12Z FRI IN ADVANCE OF NEXT 
RAPIDLY APPROACHING SYSTEM. EXPECT CONDITIONS TO IMPROVE TO VFR 
CIGS/VSBYS TOWARD LATE MORNING FRI.

//ATL CONFIDENCE...12Z UPDATE...
LOW TO MEDIUM CONFIDENCE ON CIGS/VSBYS THROUGH 14Z FRI...THEN HIGH 
CONFIDENCE.
LOW TO MEDIUM CONFIDENCE ON WIND DIR/SPD THROUGH 18Z...THEN MEDIUM 
TO HIGH CONFIDENCE REMAINDER OF TAF VALID PERIOD.

19

.PRELIMINARY POINT TEMPS/POPS...
ATHENS          66  45  65  46 / 100   0   5   5 
ATLANTA         67  48  65  50 / 100   0   5  10 
BLAIRSVILLE     61  41  61  43 / 100   0   5  10 
CARTERSVILLE    67  44  64  44 / 100   0   5  10 
COLUMBUS        70  52  68  53 /  90  10   5  20 
GAINESVILLE     64  45  63  46 / 100   0   5  10 
MACON           70  48  69  52 /  90   5   5  20 
ROME            68  44  64  44 / 100   0   5  10 
PEACHTREE CITY  67  43  66  45 / 100   0   5  10 
VIDALIA         71  56  69  53 /  70  10  10  30 

.FFC WATCHES/WARNINGS/ADVISORIES...
NONE.