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