551 FXUS62 KFFC 250000 AFDFFC AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE PEACHTREE CITY GA 800 PM EDT WED APR 24 2013 .PREV DISCUSSION... /ISSUED 325 PM EDT WED APR 24 2013/ SHORT TERM /TONIGHT THROUGH THURSDAY/... THE MAIN ISSUE OF THE SHORT TERM ACTUALLY IS MORE IN THE NEAR- TERM WITH THE SHOWERS AND THUNDERSTORMS ASSOCIATED WITH THE FRONT PUSHING THROUGH THIS EVENING. SHOWERS BEGINNING TO MOVE INTO NORTHWEST GEORGIA AT AFD TIME AND SHOULD WORK THEIR WAY ACROSS THE FORECAST AREA OVER THE NEXT SEVERAL HOURS. CAPE VALUES AT AFD TIME ARE PRETTY MEAGER...WITH LESS THAN 250 J/KG MUCAPE SPREADING ACROSS WEST CENTRAL GEORGIA. DO NOT EXPECT ANY SEVERE WEATHER WITH THE FRONT BUT THERE SHOULD BE ENOUGH CAPE FOR THUNDER...SO HAVE KEPT THE WORDING AT SCATTERED TO NUMEROUS SHOWERS WITH ISOLATED TO SCATTERED THUNDER. HOWEVER...CONVECTION INTENSIFYING ALONG THE GULF MAY HINDERING INFLOW AHEAD OF THE FRONT /NOTICE THAT MOST WINDS ACROSS GA ARE SOUTHWEST INSTEAD OF SOUTHEAST/ WHICH MAY SERVE TO FURTHER LIMIT CAPE...SO WE WILL AS USUAL HAVE THESE COMPETING EFFECTS TO DEAL WITH. ADDITIONALLY...GUIDANCE WANTS TO SORT OF STALL THE FRONT ACROSS NORTH GEORGIA AS THE SYSTEM OCCLUDES FURTHER...LIMITING THE CHANCE OF CONVECTION ACROSS CENTRAL GEORGIA WHERE THERE MIGHT BE THE CHANCE FOR CAPES TO INCREASE THIS AFTERNOON. MOST OF THE SHORT-TERM GUIDANCE...AT LEAST THE MASS FIELDS...IN GOOD AGREEMENT WITH TIMING OF THE FRONTAL PASSAGE...WITH THE STALLING ACROSS NORTH GEORGIA BETWEEN 00-06Z AND THEN FINALLY PUSHING THROUGH CENTRAL GEORGIA CLOSER TO 12Z. ENOUGH DRY AIR PUSHING IN BEHIND THE FRONT THAT IT WILL BE NOTICEABLE ACROSS THE METRO AREA TONIGHT. MAV IS A TAD COOLER WITH THE MET WHILE THE SREF AGREES MORE WITH MAV AND ECMWF MORE WITH THE MET...SO TOOK A GENERAL BLEND. IT WILL OF COURSE BE COOLER TOMORROW THAN TODAY BUT WITH FULL SUN EXPECTED IN THE AFTERNOON THAT WILL MODERATE THE EFFECTS OF THE CAA BEHIND THE FRONT...LEADING TO TEMPS ONLY A MINOR COOL-DOWN /A FEW DEGREES/. IT WILL BE FAR MORE NOTICEABLE IN LOW TEMPS FOR THE FIRST PART OF THE EXTENDED. TDP NO CHANGES NEEDED TO THE PREVIOUS EXTENDED FORECAST RATIONALE. 16 LONG TERM /THURSDAY NIGHT THROUGH WEDNESDAY/... QUIET START TO THE LONG TERM WITH HIGH PRESSURE CENTERED OVER THE OHIO AND TENNESSEE VALLEYS BEING THE DOMINATE FEATURE. THIS WILL SHIFT TO THE EAST COAST BY FRIDAY AFTERNOON AND A WET PERIOD WILL RETURN FOR THE WEEKEND THROUGH THE END OF THE EXTENDED. ECMWF AND GFS ARE IN BETTER AGREEMENT IN REGARDS TO THE TIMING AND STRENGTH OF THE UPPER LEVEL SHORT WAVE PROGGED TO SHIFT FROM THE MIDDLE PLAINS FRIDAY NIGHT INTO THE TENNESSEE VALLEY BY SUNDAY. DESPITE BETTER AGREEMENT OF TIMING OF THE SHORTWAVE...GFS AND ECMWF DIFFER ON TIMING OF PRECIP RETURNING TO CWA. ECMWF APPEARS TO BE THE FASTEST WITH BRINGING PRECIP IN THE FIRST HALF OF FRIDAY NIGHT...NAM AND SREF ARE IN BETWEEN THE GFS AND ECMWF WITH BRINGING IN PRECIP THE SECOND HALF OF FRIDAY NIGHT...WHILE THE GFS IS THE SLOWEST AND HOLDS IT OFF UNTIL SATURDAY. HAVE GONE BASICALLY WITH AN AVERAGE AND STARTED INTRODUCING POPS AGAIN FRIDAY NIGHT. ALTHOUGH THE SHORTWAVE SHIFTS EAST OF THE CWA BY SUNDAY NIGHT...ACTIVE PATTERN STILL REMAINS THROUGH THE LONG TERM. UPPER RIDGE BUILDS ACROSS THE CWA BY TUESDAY...HOWEVER THIS DOES NOT REALLY HAVE A ROLE IN SUPPRESSING CONVECTION ACROSS THE AREA IN THE GFS SOLUTION. IT WILL ONLY SERVE TO HELP INCREASE OUR MAX TEMPS. ECMWF IS STRONGER WITH THE RIDGE AND SUPPRESSES CONVECTION SOMEWHAT BUT THINK THE RIDGE MAY BE TOO STRONG SO LEANING TOWARD THE GFS AND STILL CARRYING CHANCE POPS IN THE FORECAST. INSTABILITY AS DEPICTED BY THE GFS IS CONSIDERABLY LESS IN THE 00Z RUN AS COMPARED TO 24 HOURS AGO AND NOW LOOKS A LITTLE TOO LOW. EXCEPT FOR WHEN THE RAIN BEGINS MOVING IN FRIDAY NIGHT...EACH DAY IS CONDUCIVE TO THUNDERSTORMS. 11 && .AVIATION... 00Z UPDATE...SECOND RAIN SHIELD TO MOVE THROUGH WHICH IS ASSOCIATED WITH THE ACTUAL FRONTAL BOUNDARY. THIS FRONT IS ABOUT 2 HOURS BEHIND SCHEDULE AND WILL ADJUST WIND SHIFT AND MVFR CIG ARRIVAL ACCORDINGLY. THERE HAS BEEN PLENTY OF IFR TO THE WEST WITH THIS SYSTEM BUT INDICATIONS ARE IT HAS BEEN DISSIPATING AS IT SHIFTS EAST AND WILL STICK WITH CURRENT MVFR FORECAST. HAVE PUSHED MVFR ENDING TIME BACK AS WELL TO 08Z FOR THE NORTHERN MOST SITES. //ATL CONFIDENCE...00Z UPDATE... MEDIUM ON CIGS AND TIMING. HIGH ON REMAINING ELEMENTS. DEESE && .PRELIMINARY POINT TEMPS/POPS... ATHENS 51 72 44 76 / 50 5 0 0 ATLANTA 48 70 47 75 / 60 0 0 0 BLAIRSVILLE 42 67 41 71 / 50 5 0 0 CARTERSVILLE 44 69 40 77 / 50 5 0 0 COLUMBUS 54 76 47 78 / 50 0 0 0 GAINESVILLE 48 71 45 74 / 60 5 0 0 MACON 54 75 42 77 / 40 5 0 0 ROME 43 71 39 77 / 40 5 0 0 PEACHTREE CITY 47 72 39 76 / 60 0 0 0 VIDALIA 61 78 53 78 / 20 10 0 0 && .FFC WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SHORT TERM...DEESE LONG TERM....BDL AVIATION...DEESE