736 FXUS62 KFFC 091817 AFDFFC AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE PEACHTREE CITY GA 217 PM EDT THU APR 9 2015 .PREV DISCUSSION... /ISSUED 1139 AM EDT THU APR 9 2015/ UPDATE... HAVE MADE A FEW MINOR ADJUSTMENTS TO THE FORECAST TO ACCOUNT FOR LATEST WARMING TRENDS. HAVE PUSHED THE AFTERNOON HIGHS UP A DEGREE OR TWO...PUTTING ATLANTA CLOSER TO BUT STILL BELOW THE RECORD HIGH FOR TODAY. OVERALL HI-RES MODELS CONTINUE SHOW ENOUGH CHANCE FOR AN ISOLATED STORM THIS AFTERNOON TO LEAVE CURRENT POPS IN PLACE. WILL LOOK MORE CLOSELY AT MAKING MORE SIGNIFICANT ADJUSTMENTS WITH THE AFTERNOON FORECAST PACKAGE. 31 PREV DISCUSSION... /ISSUED 731 AM EDT THU APR 9 2015/ PREV DISCUSSION... SHORT TERM /TODAY THROUGH FRIDAY/... /ISSUED 357 AM EDT THU APR 9 2015/ FOCUS OF THE SHORT TERM IS ON A COLD FRONT THAT WILL PUSH THROUGH THE CWA ON FRIDAY. AHEAD OF THIS FRONT...THE UPPER LEVEL FLOW WILL TRANSITION FROM ZONAL TO MORE SW...AND THIS ALIGNS WITH THE SW FLOW AT THE SFC. QUITE A DIFFERENCE TODAY BETWEEN MODELS IN TERMS OF THE ACCUMULATED PRECIP. NAM IS ON THE DRIER SIDE WHILE THE GFS IS ON THE WET SIDE AND THE ECMWF AND SREF ARE IN THE MIDDLE. HI-RES MODELS ARE SUGGESTING ISOLD DEVELOPMENT TODAY. FOR THE MOST PART IN THE FORECAST...ENDED UP WITH SLIGHT CHANCE OF SHOWERS AND THUNDERSTORMS BEGINNING THIS AFTERNOON. WITH INSTABILITY VALUES AROUND 1500-2000 J/KG...IF STORMS DO DEVELOP...COULD NOT COMPLETELY RULE OUT AN ISOLATED STRONG TO SEVERE STORM. SHOWERS AND THUNDERSTORMS ASSOCIATED WITH THE FRONT MOVE INTO NW PART OF THE CWA BY SUNRISE ON FRIDAY. WITH THE FRONT MOVING THROUGH ON FRIDAY HAVE CONTINUED WITH THE LIKELY TO CATEGORICAL RAIN CHANCES. INSTABILITY ON FRIDAY RANGES FROM 1500-2500 J/KG ACROSS THE GFS AND NAM...SO PLENTY OF INSTABILITY ACROSS THE CWA. LOW LEVEL AND DEEP LAYER SHEAR ARE ON THE LOWER SIDE. HIGHEST 0-1KM HELICITY VALUES ARE RIGHT AROUND 12Z ACROSS THE NW WITH GFS FORECAST VALUES JUST EXCEEDING 200. NAM IS LOWER AROUND THIS TIME AND DEPICTS THE HIGHER VALUES EARLIER IN THE NIGHT AND AGAIN DURING THE DAY FRIDAY AS THE FRONT COMES THROUGH. SPC HAS THE NW IN THE MARGINAL FOR DAY 1 AND THE AREA IN A COMBINATION OF MARGINAL AND SLIGHT RISK FOR DAY 2. EXPECT A LINE OF THUNDERSTORMS AHEAD OF THE FRONT AND EVEN THOUGH THE SHEAR IS ON THE LOWER SIDE...PLENTY OF INSTABILITY THAT THE CWA COULD SEE A FEW STRONG TO SEVERE STORMS ON FRIDAY. THE MAIN THREATS CONTINUE TO BE WIND AND HAIL. FORECAST HIGH TEMPERATURES FOR TODAY CONTINUE TO REMAIN WELL ABOVE NORMAL...WITH THE FORECAST AROUND 2-3 DEGREES BELOW THE RECORDS. FOR FRIDAY MORNING...FORECAST IS TO TIE THE WARMEST MIN TEMP FOR THE DAY AT ATL AND ONE DEGREE ABOVE THE WARMEST MIN TEMP AT AHN. WITH FRONT MOVING IN ON FRIDAY...HIGH TEMPERATURES DECREASE AND THUS NO NEAR RECORD TEMPS. 11 LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/... /ISSUED 357 AM EDT THU APR 9 2015/ MODELS IN GOOD AGREEMENT THROUGH THIS WEEKEND...THEN TIMING AND STRENGTH DIFFERENCES OCCUR FOR THE REST OF THE LONG TERM. HAVE THEREFORE BROAD BRUSHED POPS NEXT WEEK DUE TO UNCERTAINTY. FOR THIS WEEKEND THE COLD FRONT WILL LINGER ACROSS SOUTH GA/NORTH FL KEEPING A CHANCE OF SHOWERS ACROSS THE SOUTHERN COUNTIES IN OUR CWA THROUGH SUNDAY. THEN AS THE H5 LOW MOVES INTO THE SOUTHERN PLAINS EARLY NEXT WEEK...WE GET INTO A SOUTHWEST FLOW WHICH WILL SPREAD MOISTURE ACROSS THE CWA BRINGING A HIGHER CHANCE OF SHOWERS/TSTORMS. 17 CLIMATE... RECORDS FOR 04-09 MAX TEMPERATURE MIN TEMPERATURE STATION HIGH LOW HIGH LOW ------- ---------- ---------- ---------- ---------- KAHN 89 1919 48 2003 67 1999 32 2000 1972 KATL 86 2011 47 1899 68 1999 32 2000 1995 1896 KCSG 89 1978 56 1989 70 1999 34 2000 KMCN 91 1978 53 1916 69 1999 32 2000 1899 && .AVIATION... 18Z UPDATE... VFR CONDITIONS EXPECTED THROUGH MUCH OF THE OVERNIGHT PERIOD...WITH MVFR ACCOMPANYING THE FRONT AND LINE OF CONVECTION PUSHES INTO NORTHWEST GEORGIA BETWEEN 09-12Z...AND THEN INTO THE ATL AREA GENERALLY 15-18Z...AND THEN THE CSG AND MCN AREAS 20Z-00Z. CLEARING CONDITIONS ARE EXPECTED BEHIND THE CONVECTION. SW WINDS EXPECTED THROUGH THE PERIOD WITH SPEEDS 10-15KT TODAY...3-7KT OVERNIGHT...AND THEN 8-10KT AFTER 14Z. GUSTY AND VRB WINDS EXPECTED WITH THE CONVECTION. A SHIFT TO THE NW IS EXPECTED 00Z SATURDAY OR AFTER. //ATL CONFIDENCE...18Z UPDATE... HIGH CONFIDENCE THROUGH 14Z. MEDIUM CONFIDENCE THEREAFTER. 31 && .PRELIMINARY POINT TEMPS/POPS... ATHENS 87 66 80 56 / 30 30 70 60 ATLANTA 85 66 78 57 / 20 20 70 60 BLAIRSVILLE 81 62 71 47 / 30 50 80 20 CARTERSVILLE 86 65 75 51 / 20 50 80 30 COLUMBUS 88 65 81 61 / 20 20 50 70 GAINESVILLE 83 65 75 54 / 30 40 80 40 MACON 88 65 82 63 / 20 10 40 70 ROME 85 65 75 50 / 20 50 80 20 PEACHTREE CITY 85 64 79 55 / 20 20 70 70 VIDALIA 87 65 86 66 / 10 10 30 60 && .FFC WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SHORT TERM...31 LONG TERM....SNELSON AVIATION...31