Area Forecast Discussion
Issued by NWS Atlanta, GA

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000 FXUS62 KFFC 291749 AFDFFC AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE PEACHTREE CITY GA 149 PM EDT SAT AUG 29 2015 .PREV DISCUSSION...
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/ISSUED 1134 AM EDT SAT AUG 29 2015/ UPDATE... HAVE TRENDED POPS DOWN ACROSS PORTIONS OF NORTH GEORGIA INCLUDING THE ATLANTA METRO AREA BASED UPON LATEST RADAR AND SATELLITE LOOPS. HI-RES MODELS SEEM TO HAVE A GOOD HANDLE ON WEAK UPPER IMPULSES MOVING INTO CENTRAL GA THIS MORNING AND TRAJECTORY OF IMPULSES AND VORT MAX WOULD KEEP BULK OF AFTERNOON PRECIP FURTHER SOUTH AND EAST. HAVE ALSO INCREASED CLOUD COVER WHICH MAY HELP INHIBIT DEVELOPMENT OF THUNDERSTORMS. HAVE LIMITED THUNDER TO AREAS WHERE HIGHEST POPS ARE AND ONLY KEPT AN ISOLATED CHANCE. MINOR TWEAKS MADE TO TEMPERATURES AS THOSE ARE MAINLY ON TRACK FOR THIS AFTERNOON. UPDATED FORECASTS ISSUED SHORTLY. PREV DISCUSSION... /ISSUED 332 AM EDT SAT AUG 29 2015/ SHORT TERM /TODAY THROUGH SUNDAY/... UPPER LOW PRESSURE ALONG THE CENTRAL GULF COAST BRINGING DEEP MOISTURE N ACROSS THE AREA TODAY AS A SHORT WAVE IN THE UPPER FLOW ENHANCES SHWR CHANCES. SURFACE HIGH PRESSURE NOSING DOWN THE EASTERN APPALACHIANS WILL AID IN A SHARP GRADIENT OF PRECIP CHANCES OVER THE FAR EASTERN COUNTIES...MAKING IT A DIFFICULT POP FORECAST. FORECAST INSTABILITY RATHER LOW SO THUNDERSTORMS CHANCES ARE RATHER MINIMAL WITH THE GREATEST CHANCES OVER THE WESTERN AND SOUTHERN AREAS. THE UPPER LOW IS FORECAST TO MOVE TO THE SOUTHERN APPALACHIANS FOR SUNDAY. THIS WILL SHIFT THE GREATEST POPS TO THE NORTHERN AND EASTERN AREAS. JUST A LITTLE MORE INSTABILITY FORECAST AS THE UPPER LOW MOVES TO THE NNE. FORECAST HIGH TEMPERATURES RUNNING 5-10 DEGREES BELOW NORMAL TODAY AND 4-8 DEGREES BELOW NORMAL FOR SUNDAY. OVERALL CONFIDENCE IS MEDIUM. BDL LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/... EXTENDED PORTION CONTINUES TO BE FRAUGHT WITH UNCERTAINTY DUE TO THE PRECARIOUS STATUS OF TROPICAL STORM ERIKA AND THE RESULTANT IMPACT ON MODEL GUIDANCE SOLUTIONS. LATEST OFFICIAL FORECAST FROM THE HURRICANE CENTER HAS ERIKA TRACKING JUST TO THE WEST OF THE FLORIDA PENINSULA AND WINDING UP AS A DEPRESSION OVER SOUTH GEORGIA WED EVENING. THIS SOLUTION CONTINUES TO HAVE SUPPORT FROM FROM THE LATEST ROUND OF OPERATIONAL MODELS INCLUDING THE GFS AND TO A LARGE EXTENT THE PREVIOUS RUN OF THE ECMWF. THE BIG QUESTIONS THEN BECOME...DOES ERIKA ACTUALLY FOLLOW THIS PATH OR DOES THE TREND WESTWARD CONTINUE AND IF IT DOES FOLLOW THIS PATH...WHAT HAPPENS AFTER IT MAKES ITS APPEARANCE OVER SOUTH GEORGIA. FOR THIS FORECAST...WILL OF COURSE GO WITH THE NHC FORECAST THROUGH WED EVENING AND THEN LEAN HEAVILY ON THE GFS FOR POP DISTRIBUTION BUT SUBDUE THE REALLY HIGH VALUES BASED ON THE CONTINUED UNCERTAINTY. SO FOR THE FORECAST...MONDAY COULD BE THE FIRST DAY THAT WE REALLY SEE THE TROPICAL MOISTURE MAKE IT INTO THE SOUTHERN SECTIONS OF THE FORECAST AREA. SHARP GRADIENT THOUGH TO DEEP MOISTURE WITH ONLY 1.30 INCH PRECIPITABLE WATER VALUES FROM THE ATLANTA METRO NORTHWARD. WILL GO AROUND LIKELY FROM CSG TO MCN AND POINTS SOUTHWARD FOR THIS TIME PERIOD. MAIN SLUG OF TROPICAL MOISTURE LOOKS TO SLOWLY CREEP NORTHWARD THROUGH MID WEEK WITH 2 INCH PW VALUES ENCROACHING UPON ATLANTA BY LATE WED AND TROPICAL MOISTURE ENGULFING MOST ALL OF THE AREA BY FRIDAY. AGAIN...IN NORMAL CIRCUMSTANCES WITH THE VALUES PRESENT...LIKELY POPS WOULD BE A GIVEN IF NOT HIGHER. BUT WITH THE AMOUNT OF UNCERTAINTY PRESENT AND THE DISTINCT POSSIBILITY THAT POPS COULD ACTUALLY BE BELOW CLIMO IF ERIKA TRACKS FURTHER WEST...WILL LIMIT POPS TO HIGH END CHANCE FOR NOW. LIKEWISE...WILL NOT GO AS COOL ON AFTERNOON HIGHS AS MODELS SUGGEST ON THE CHANCE THAT WE SEE A DRIER WEEK THAN THE GFS IS ADVERTISING. DEESE
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&& .AVIATION...
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18Z UPDATE... AN AREA OF SHOWERS CONTINUES TO SPREAD NORTHWARD WITH -SHRA IN/AROUND ALL BUT CSG. -SHRA WILL CONTINUE OFF AND ON THROUGH THE FORECAST PERIOD. ISOLATED THUNDERSTORMS WILL BE POSSIBLE OVER CSG/MCN. CIGS WILL BE LOW VFR AND MVFR WITH HEAVIER RAIN. BY DAYBREAK IFR WILL BE POSSIBLE...ESPECIALLY IN RAIN SATURATED AREAS. WINDS WILL REMAIN OUT OF THE EAST AT 5-10 KTS DURING THE DAY AND DIMINISHING TO 4-7KTS OVERNIGHT. //ATL CONFIDENCE...18Z UPDATE... LOW TO MEDIUM CONFIDENCE IN TIMING OF PRECIP MEDIUM CONFIDENCE IN CIGS/VISIBILITY MEDIUM TO HIGH CONFIDENCE IN WINDS ATWELL
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&& .PRELIMINARY POINT TEMPS/POPS...
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ATHENS 84 68 81 67 / 40 40 50 30 ATLANTA 83 68 82 69 / 50 50 50 30 BLAIRSVILLE 80 63 76 62 / 30 30 50 30 CARTERSVILLE 84 67 81 66 / 40 40 50 30 COLUMBUS 82 70 86 71 / 70 50 50 30 GAINESVILLE 82 67 78 67 / 40 40 50 30 MACON 83 69 85 69 / 70 50 50 30 ROME 85 68 82 66 / 40 40 50 30 PEACHTREE CITY 82 68 83 68 / 60 50 50 30 VIDALIA 86 71 86 71 / 60 50 50 30
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&& .FFC WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SHORT TERM...ATWELL LONG TERM....NLISTEMAA AVIATION...ATWELL

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