978 
FXUS62 KFFC 100020
AFDFFC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PEACHTREE CITY GA
820 PM EDT TUE APR 9 2013



.UPDATE...
HAVE MADE SOME MINOR CHANGES TO HOURLY TEMPERATURES AND DEW POINTS
THROUGH THE OVERNIGHT PERIOD. OVERALL...FORECAST LOOKS TO BE ON
TRACK. SOUTHERLY FLOW IS EXPECTED TO CONTINUE TO USHER MOISTURE
INTO THE REGION...AND IS EXPECTED TO SUPPORT PATCHY FOG
DEVELOPMENT TONIGHT THROUGH WEDNESDAY MORNING.

NO ADDITIONAL UPDATES ARE EXPECTED AT THIS TIME.

31

&&

.PREV DISCUSSION... /ISSUED 320 PM EDT TUE APR 9 2013/ 

..SEVERE STORMS EXPECTED THURSDAY INTO THURSDAY NIGHT...

SHORT TERM /TONIGHT THROUGH WEDNESDAY NIGHT/...

ALL IN ALL CONTINUED QUIET WEATHER THROUGH THE SHORT TERM AS 
MID-UPPER LEVEL RIDGING CONTINUES OVER THE AREA AND SUPPRESSES
CHANCES FOR ANY PRECIP ACTIVITY. RIDGE BEGINS TO WEAKEN WEDNESDAY 
NIGHT AS A COLD FRONT MOVES ACROSS THE MS VALLEY BRINGING ONLY SMALL 
CHANCES FOR LIGHT SHOWERS TO FAR N GA.

MOISTURE TRAPPED UNDER THE INVERSION ALOFT PLAYING HAVOC WITH THE 
CLOUD COVER FORECAST. AFTERNOON CU DEVELOPMENT IS EXPECTED TO 
DIMINISH AND DISSIPATE WITH THE LOSS OF DAY TIME HEATING. 

SURFACE HIGH REMAINS OFF THE ATLANTIC COAST WITH A WARM AND RATHER 
MOIST LOW LEVEL SOUTHERLY FLOW CONTINUING. WEAK UPPER LEVEL DISTURBANCES 
BUCKING THE UPPER RIDGE COULD SERVE TO ENHANCE CU DEVELOPMENT FOR 
WEDNESDAY AND THIS WILL NEED TO BE MONITORED. 

THE TREND OF WELL ABOVE NORMAL TEMPERATURES WILL CONTINUE. GUIDANCE 
IS IN DECENT AGREEMENT THROUGH THE SHORT TERM AND TOOK A GENERAL 
BLEND OF WINDS/DEWPOINTS AND MAX/MIN TEMPERATURES. FORECAST LOW 
TEMPERATURES RUNNING 6-10 DEGREES ABOVE NORMAL TONIGHT AND AROUND 12 
DEGREES ABOVE NORMAL WEDNESDAY NIGHT. FORECAST HIGH TEMPERATURES 
RUNNING 8-11 DEGREES ABOVE NORMAL FOR WEDNESDAY.

OVERALL CONFIDENCE IS HIGH.

BDL

LONG TERM /THURSDAY THROUGH TUESDAY/...

SUBTLE CHANGES IN THE LATEST LONG TERM MODEL RUNS BUT STILL
AWAITING LATEST EURO BEFORE MAKING FINAL DECISIONS. OVERALL THOUGH
IT LOOKS AS THOUGH MODELS ARE HONING IN ON A SOLUTION AS GFS IS A
LITTLE SLOWER THIS RUN WHICH PUTS IT CLOSER TO THE PREVIOUS EURO.
NAM12 NOW SOMEWHERE IN THE MIDDLE WHICH IS ACTUALLY A GOOD
COMPROMISE TO USE FOR THIS FORECAST CYCLE. THIS WOULD BRING THE
MAIN SQUALL LINE INTO NORTHWEST GEORGIA THURSDAY AFTERNOON AND
INTO CENTRAL GEORGIA DURING THE LATE EVENING TO SHORTLY AFTER
MIDNIGHT. AS FAR AS SEVERE POTENTIAL...GFS AND NAM12 NOW SHOWING
CAPE IN EXCESS OF 1000 J/KG OVER THE SOUTHERN MOST ZONES WITH
INSTABILITY AXIS NOW EXTENDING THROUGH ENTIRE FORECAST AREA. IT
APPEARS WITH THIS SYSTEM SOUTHERN STREAM AND NORTHERN STREAM JET
WILL COME INTO PHASE ALLOWING FOR A SECONDARY POTENT SHORTWAVE TO
ROTATE THROUGH WHICH SHOULD ENHANCE SQUALL LINE AS IT PUSHES
THROUGH. LOW LEVEL JET INCREASE TO 50 KTS AT THIS TIME AS WELL
WITH BOWING SEGMENTS LIKELY ROUGHLY FROM A LA GRANGE TO AHN LINE.
SHOULD THIS PHASING OCCUR...WOULD EXPECT A LARGE AREAL EXTENT OF
DAMAGING WINDS AND CONTINUED POSSIBILITIES OF TORNADOES GIVEN
MODERATE LOW LEVEL HELICITY. HAIL WILL ALSO BE POSSIBLE WITH
STRONGER STORMS IN TALLER CORES TO THE SOUTH. CIPS ANALOG SITE
SHOWS A WIDE RANGE OF POSSIBILITIES FOR THE MOST COMPARABLE STORMS
BUT THE ONES IDENTIFYING SIMILAR SHORTWAVE AND CAPE GENERALLY AGREE
ON DECENT SEVERE WX COVERAGE AND WILL RAMP UP LOCAL PRODUCTS ACCORDINGLY.

DEESE

PREV DISCUSSION... /ISSUED 739 AM EDT TUE APR 9 2013/ 

LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
THE GFS REMAINS SLIGHTLY FASTER THAN THE ECMWF WITH REGARDS TO
TIMING OF NEXT FRONTAL PASSAGE... WITH GFS PUSHING THE COLD FRONT
INTO NW GA EARLY THURSDAY EVENING... AND ECMWF NOT UNTIL MIDNIGHT
OR LATER FOR THIS SAME LOCATION. DESPITE MODEL DIFFERENCES...
CONFIDENCE IS INCREASING THAT AT LEAST ISOLATED SEVERE STORMS WILL
ACCOMPANY THIS STORM SYSTEM. ALTHOUGH MODEL INSTABILITIES APPEAR
MODEST... WITH MAYBE 400-800 MLCAPE SPREADING INTO NORTH GA THURSDAY
AFTERNOON AND EVENING... BOTH MODELS SHOW A STRONG UPPER DISTURBANCE
STRENGTHENING WIND PROFILES... WHICH WOULD SERVE TO ENHANCE
EXPECTED SQUALL LINE CONVECTION PUSHING ACROSS ALABAMA AND INTO NW
AND WEST CENTRAL GA LATE THURSDAY AFTERNOON OR EARLY EVENING
AHEAD OF THE APPROACHING COLD FRONT. AT THIS TIME... IT APPEARS
THE MAIN THREAT WOULD BE DAMAGING WINDS FROM BOWING ECHOES EMBEDDED
WITHIN THE EXPECTED SQUALL LINE. HOWEVER... A LOW CAPE...HIGH WIND
SHEAR ENVIRONMENT WOULD SUPPORT A FEW TORNADOES... ESPECIALLY IF
ANY ISOLATED SUPER CELL STORMS CAN DEVELOP OUT AHEAD OF THE SQUALL
LINE. ALTHOUGH STRONG TO SEVERE STORMS WILL BE POSSIBLE ACROSS ALL
OF NORTH AND CENTRAL GA PER LATEST DAY 3 OUTLOOK FROM SPC...
TIMING OF UPPER SUPPORT WOULD SUGGEST THE GREATEST SEVERE THREAT
WOULD BE GENERALLY ALONG AND WEST OF AN AMERICUS TO COVINGTON TO
BLAIRSVILLE LINE... AND MAINLY FROM LATE THURSDAY AFTERNOON THROUGH
MAYBE 4 AM FRIDAY MORNING. HOWEVER... THIS COULD CHANGE... AND ALL
INTEREST ACROSS NORTH AND CENTRAL GA ARE ADVISED TO CLOSELY MONITOR
LATER FORECAST CONCERNING THIS NEXT POTENTIALLY DANGEROUS WEATHER
SYSTEM. THE HEAVIEST RAINFALL AMOUNTS STILL APPEAR TO BE ACROSS
NORTH AND WEST CENTRAL GA WHERE 1 TO 2 INCHES ARE EXPECTED... WITH
GENERALLY AN INCH OR LESS LIKELY ELSEWHERE. OTHERWISE... EXPECT
CLEARING CONDITIONS ON FRIDAY BEHIND THE DEPARTING COLD FRONT WITH
HIGH PRESSURE IN CONTROL THROUGH AT LEAST EARLY SUNDAY. AS THE
SURFACE RIDGE SLIPS EAST... A MOIST SOUTHERLY WIND FLOW COULD BE
ENHANCED BY AN ACTIVE WESTERLY FLOW ALOFT TO BRING ISOLATED SHOWERS
BACK INTO THE FORECAST FOR LATE SUNDAY INTO MONDAY. HAVE KEPT COVERAGE
ISOLATED WITH NO MENTION OF THUNDER FOR NOW. 39 

&&

.AVIATION...
00Z UPDATE...
VFR CONDITIONS EXPECTED TO CONTINUE THROUGH THE TAF VALID PERIOD.
MOIST SOUTHERLY FLOW IS EXPECTED TO SUPPORT PATCHY FOG THROUGH
WEDNESDAY MORNING...BUT NOT ENOUGH TO INCLUDE IN THE TAF EXCEPT
4-5 SM AT AHN AND MCN. SCT CU EXPECTED TO DEVELOP BY MID
MORNING...INCREASING TO BKN BY AFTERNOON. CLEARING EXPECTED BY
THE EVENING HOURS. WINDS WILL BE SE-SSE OVERNIGHT AT GENERALLY
3-5KT...INCREASING TO 7-9KT THROUGH THE DAY.

//ATL CONFIDENCE...00Z UPDATE...
HIGH CONFIDENCE ON ALL ELEMENTS.

31

&&

.PRELIMINARY POINT TEMPS/POPS...
ATHENS          57  83  59  75 /   0   5  10  70 
ATLANTA         60  82  63  76 /   0   5  10  70 
BLAIRSVILLE     54  80  57  70 /   0  10  20  70 
CARTERSVILLE    58  83  59  76 /   0   5  10  80 
COLUMBUS        60  84  63  77 /   0   5  10  70 
GAINESVILLE     58  82  60  73 /   0   5  10  70 
MACON           56  83  60  80 /   0   5  10  60 
ROME            57  83  59  75 /   0  10  20  90 
PEACHTREE CITY  54  81  58  76 /   0   5  10  70 
VIDALIA         62  83  66  82 /   0   5  10  40 

&&

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

$$

SHORT TERM...31
LONG TERM....41
AVIATION...31