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000
FXUS62 KFFC 170119 AAB
AFDFFC

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE PEACHTREE CITY GA
919 PM EDT THU MAY 16 2013

.UPDATE...
MAIN CHANGE WAS TO POP AND WEATHER GRIDS. HAVE REMOVED MENTION OF
THUNDER FOR THE REMAINDER OF TONIGHT. HAVE ALSO REDUCED POPS AND
FOCUSED THE SLIGHT CHANCE OF SHOWERS MORE ON THE WESTERN SIDE
GIVEN PROXIMITY TO SOME SHOWERS OVER AL. ALTHOUGH VORT MAX IS
PEGGED TO MOVE ACROSS NW GA AROUND SUNRISE...BETTER CHANCE OF
RAIN APPEARS TO BE IN THE AFTERNOON TOMORROW. DID REDUCE POPS
SLIGHTLY AND CUT BACK ON THE AREA FOR TOMORROW MORNING AND
AFTERNOON AS THE BETTER CHANCES APPEAR TO BE ACROSS NORTH GEORGIA.

BESIDES AFOREMENTIONED CHANGES...REST OF TWEAKS TO THE FORECAST
WERE ONLY MINOR TO ACCOUNT FOR HOURLY TRENDS.

11

&&

.PREV DISCUSSION...

SHORT TERM /TONIGHT THROUGH FRIDAY NIGHT/...
/ISSUED 309 PM EDT THU MAY 16 2013/
SCATTERING OF MIDLEVEL CLOUDS CONTINUES WITH A CU FIELD DEVELOPING
ACROSS PORTIONS OF THE NORTH. A SLIGHT CHANCE FOR SHOWERS AND
THUNDERSTORMS SHOULD REMAIN NORTH OF ATL WITH THE GREATEST CHANCE IN
FAR NORTH GEORGIA THIS AFTERNOON AND EVENING.

MODELS ARE IN DECENT AGREEMENT WITH THE MAIN INFLUENCING FEATURES IN
THE SHORT TERM SO HAVE GONE WITH GENERAL BLEND. LOW PRESSURE SYSTEM
ACROSS THE SOUTHERN PLAINS LOOKS TO CONTINUE TO DAMPEN INTO THE MAIN
LONGWAVE ENERGY AS IT MOVES SLOWLY EASTWARD. THIS SHOULD MAINLY
SERVE TO BRING AN ENHANCED MOISTURE FIELD TO THE NORTHERN PORTION OF
THE AREA WITH SOME WEAK SHORTWAVE VORTICITY ADVECTION ADDING SOME
ADDITIONAL FORCING FOR ASCENT. FORECAST CAPE VALUES NEAR 1000-1500
J/KG IN A WEAKLY SHEARED ENVIRONMENT WILL ALLOW FOR THUNDERSTORM
DEVELOPMENT HAVING THE MAIN THREATS OF OCCASIONAL LIGHTNING...GUSTY
WINDS...AND BRIEF HEAVY RAINFALL. MOISTURE AND INSTABILITY WILL BE
ON THE RISE THIS WEEKEND...WHEN THERE WILL BE A GREATER CHANCE FOR SOME
STRONG STORMS.

FOR TEMPS...A GENERAL BLEND OF GUIDANCE LOOKS REASONABLE WITH VALUES
CONTINUING TO BE AROUND 3-5 DEGREES ABOVE NORMAL.

BAKER

LONG TERM /SATURDAY THROUGH THURSDAY/...
/ISSUED 309 PM EDT THU MAY 16 2013/
MODELS STILL IN GENERAL AGREEMENT WITH ENHANCED MOISTURE ACROSS
THE AREA OVER THE WEEKEND AND INTO NEXT WEEK. ALTHOUGH QPF BETWEEN
THE MODELS CONTINUES TO DISAGREE...EVEN THE DRIEST OF THE MODELS
STILL ADVERTISING WIDESPREAD 1-1.5 INCHES OF RAINFALL THROUGH
MONDAY. HAVE GENERALLY MADE ONLY MINOR TWEAKS TO TEMPERATURES AND
POPS TO ACCOUNT FOR LATEST MODEL TRENDS...BUT WITH UNCERTAINTY IN
THE PLACEMENT OF THE PRECIP...HAVE AVOID MAKING WHOLESCALE CHANGES
AT THIS TIME. FOR SATURDAY...MODELS AGREE ENOUGH TO GO AHEAD WITH
LIKELY POPS ACROSS PORTIONS OF NORTHEAST GEORGIA. THUNDERSTORMS
CONTINUE TO BE ADVERTISED IN GRIDS...AND MODELS CONTINUE TO FOCUS
ON MORE DIURNALLY DRIVEN CONVECTION. FOR NOW...HAVE CONTINUED WITH
MUCH OF THE PREVIOUS FORECAST...AND THE PREVIOUS FORECAST
DISCUSSION IS INCLUDED BELOW.

31

/ISSUED 335 AM EDT THU MAY 16 2013/
STALLED FRONTAL BOUNDARY JUST TO THE NORTH OF THE CWFA WILL
REMAIN THE FOCUS FOR CONVECTIVE ACTIVITY THROUGH EARLY NEXT WEEK.
THE BOUNDARY WILL BEGIN TO SHIFT NORTHWARD BY TUESDAY AS A COLD
FRONT ENTERS THE LOWER MISSISSIPPI RIVER VALLEY. THE COLD FRONT IS
EXPECTED TO IMPACT THE CWFA WEDNESDAY INTO THURSDAY.

A WEAKENING UPPER LOW WILL INTERACT WITH THE STALLED BOUNDARY ON
SATURDAY...SO HAVE RAISED POPS ACROSS THE BOARD. THE HIGHEST POPS
WILL BE ACROSS NORTHERN GA...CLOSEST TO THE FRONT. HOWEVER...WITH
ABUNDANT MOISTURE FUNNELING NORTHWARD FROM THE GULF....SOME SURFACE
INSTABILITY...AND STEEPENING LAPSE RATES WITH THE COLD POOL
ALOFT...HAVE ALSO RAISED POPS TO LOW END SCT/SLIGHT CHANCE FOR THE
REMAINDER OF THE CWFA. DO THINK CONVECTION WILL DIMINISH IN COVERAGE
AS THE LOW MEANDERS OFF TO THE EAST.

POPS WILL REMAIN SCT/ISO FOR THE REMAINDER OF THE WEEKEND INTO THE
FIRST PART OF NEXT WEEK. THE ONLY REAL SURFACE MECHANISM TO FOCUS
PRECIP WILL BE TO THE NORTH...BUT WEAK SHORTWAVES IN THE FLOW COULD
ENHANCE ANY DIURNAL CONVECTION THAT DEVELOPS. THE WARM
FRONT/STATIONARY BOUNDARY WILL BEGIN TO SHIFT NORTHWARD INTO THE
MIDDLE ATLANTIC ON TUESDAY AS THE COLD FRONT BEGINS TO APPROACH THE
MISSISSIPPI RIVER.

MODELS HAVE SLOWED THE FROPA A LITTLE...WITH THE FRONT COMING
THROUGH THE CWFA LATE WEDNESDAY INTO EARLY THURSDAY.

NLISTEMAA

AVIATION...
00Z UPDATE...
/ISSUED 751 PM EDT THU MAY 16 2013/
VFR CONDITIONS EXPECTED THROUGH THE TAF PERIOD. HIGH CLOUDS WILL
MOVE IN TONIGHT AND CU FIELD WITH SCT050 WILL DEVELOP AGAIN
TOMORROW AFTERNOON. WINDS ARE THE GREATEST CHALLENGE IN THE
FORECAST. SHOULD REMAIN SSW TONIGHT. BY TOMORROW EVENING...THERE
IS SOME UNCERTAINTY AGAIN IN THE WIND DIRECTION FORECAST. FOR NOW
ADVERTISING SSW AROUND 00Z TOMORROW NIGHT...BUT COULD BECOME SSE.

//ATL CONFIDENCE...00Z UPDATE...
HIGH CONFIDENCE ON ALL ELEMENTS EXCEPT MEDIUM ON WIND DIRECTION
TONIGHT AND FRIDAY NIGHT.

11

&&

.PRELIMINARY POINT TEMPS/POPS...
ATHENS          60  85  62  83 /  10  20  20  40
ATLANTA         64  83  65  82 /  10  20  30  40
BLAIRSVILLE     56  77  60  76 /  10  40  40  70
CARTERSVILLE    59  81  62  81 /  10  30  30  50
COLUMBUS        63  85  65  86 /  10  10  10  30
GAINESVILLE     62  82  63  79 /  10  30  30  50
MACON           59  86  62  86 /  10  10  10  30
ROME            59  82  63  81 /  20  30  30  50
PEACHTREE CITY  57  83  61  83 /  10  20  20  30
VIDALIA         65  87  67  88 /  10  10  10  20

&&

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

$$

SHORT TERM...11
LONG TERM....39
AVIATION...11