190  
FXUS62 KFFC 010103  
AFDFFC  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE PEACHTREE CITY GA  
903 PM EDT WED AUG 31 2016  
 
UPDATE...  
GREATEST UPCOMING FORECAST CONCERN IS TROPICAL STORM HERMINE  
CURRENTLY LOCATED IN THE EASTERN GULF OF MEXICO.  
 
AS PER RECENT RADAR IMAGERY...REMAINING SHOWER/CONVECTIVE  
ACTIVITY MAINLY CONFINED TO NORTH GA WHERE A LEE SFC TROUGH HAS  
PROVIDED NECESSARY LIFT AMIDST DIURNAL HEATING THIS AFTERNOON.  
SHOWER ACTIVITY IS ALSO LINGERING ACROSS SE GA WHERE GREATER  
TROPICAL MOISTURE AND UPPER LEVEL SUPPORT EXISTS. EXPECT THIS  
ACTIVITY TO DIMINISH AS THE BOUNDARY LAYER DECOUPLES THIS  
EVENING. MAINLY CLEAR SKIES EXPECTED ACROSS N GA...WITH SOME PESKY  
LOW-MID LEVEL CLOUDS LINGERING ACROSS C GA. LOW TEMPS UPPER 60S  
MOUNTAINS TO LOWER 70S ELSEWHERE.  
 
FOR THURSDAY...GREATER COVERAGE OF CONVECTION EXPECTED AS TS  
HERMINE CREEPS TOWARDS THE FL PANHANDLE AND A COLD FRONT  
APPROACHES THE CWA FROM THE NW. EXPECT HIGHEST COVERAGE OF PRECIP  
ACROSS THE MOUNTAINS AHEAD OF THE COLD FRONT AND ACROSS CENTRAL GA  
WHERE DEEP LAYER TROPICAL MOISTURE RESIDES. HIGH TEMPS IN LOWER  
90S.  
 
TROPICS: TS HERMINE'S MID-LEVEL CIRCULATION IS LOCATED NE OF  
YUCATAN PENNINSULA WITH SFC REFLECTION LOCATED A TOUCH FURTHER  
NORTH. HERMINE IS EXPECTED TO MAKE LANDFALL ALONG FL COAST AFTER  
SUNSET THURS. IT IS POSSIBLE HERMINE COULD INTENSIFY INTO A  
HURRICANE BEFORE MAKING LANDFALL...WITH SSTS WELL ABOVE NORMAL  
ACROSS THE GULF. REGARDLESS OF IT BEING A HURRICANE OR TROPICAL  
STORMS...FEEL THREAT OF AT LEAST TROPICAL STORM CONDITIONS ARE  
POSSIBLE ACROSS PARTS OF CENTRAL GA NEAR THE CLOSE OF THE WORK  
WEEK. AFTER COLLABORATION WITH NEIGHBORING OFFICES THIS  
AFTERNOON...HAVE PUT TS WINDS IN THE GRIDS AS WELL AS ISSUED A TS  
AND FLASH FLOOD WATCH. IT IS IMPORTANT TO KEEP UP TO DATE WITH THE  
LATEST FORECAST INFORMATION...AS A SLIGHT SHIFT IN THE PROJECTED  
PATH COULD RESULT IN DRAMATIC CHANGES TO THE FORECAST. SEE  
PREVIOUS AFD DISCUSSION AND LATEST INFORMATION FROM NHC FOR  
FURTHER DETAILS ON THIS TS.  
 
KOVACIK  
 
PREV DISCUSSION... /ISSUED 334 PM EDT WED AUG 31 2016/  
 
.TROPICAL STORM HERMINE LIKELY TO PRODUCE SIGNIFICANT IMPACTS  
IN PARTS OF MIDDLE AND EAST GEORGIA THURSDAY NIGHT AND FRIDAY...  
 
SHORT TERM /TONIGHT THROUGH THURSDAY/...  
THE NEXT 24 HOURS SHOULD BE FAIRLY QUIET, EVEN WITH THE ACTIVE  
TROPICS. THE MAIN IMPACTS WITHIN THE FIRST THREE PERIODS WILL BE  
INCREASING CHANCES FOR PRECIPITATION...INCLUDING LOCALLY HEAVY  
RAINFALL BY THURSDAY NIGHT.  
 
DIURNAL CU AND SHOWERS SHOULD BEGIN TO DIMINISH LATE THIS  
EVENING/OVERNIGHT WITH THE LOSS OF HEATING. SKIES SHOULD MOSTLY  
CLEAR OUT ACROSS THE ATL METRO...WHILE LINGERING ACROSS CENTRAL GA  
OVERNIGHT.  
 
THE WEAK FRONTAL BOUNDARY CURRENTLY STRETCHING FROM THE EASTERN  
GREAT LAKES BACK THROUGH THE CENTRAL US WILL SLOWLY BEGIN TO SAG  
SOUTHWARD TOMORROW. THIS BOUNDARY IS EXPECTED TO SETTLE ACROSS  
NORTHERN PORTIONS OF GA BY TOMORROW NIGHT.  
 
NOT TOO CONFIDENT ON HOW FAR SOUTH THIS BOUNDARY WILL MAKE IT, BUT  
THE MODELS ARE PROGGING A BRIEF WIND SHIFT TO THE NW TOMORROW  
AFTERNOON BEFORE THE SYNOPTIC FLOW TURNS BACK TO THE EAST AHEAD OF  
HERMINE. FOR MUCH OF TOMORROW, THE POPS SHOULD BE HIGHEST ACROSS  
NORTHERN GA (WITH THE FRONT) AND CENTRAL GA (SHOWERS COMING OFF THE  
ATLANTIC IN THE DEEP EASTERLY FLOW). HAVE GONE AHEAD AND PAINTED A  
SLIGHT CHANCE ACROSS THE I-20 CORRIDOR...AS SHOWERS CAN POP UP  
ANYTIME IN THIS TYPE OF AIRMASS.  
 
NLISTEMAA  
 
LONG TERM /THURSDAY NIGHT THROUGH WEDNESDAY/...  
PRIMARY CONCERN IS TIMING AND IMPACTS OF HERMINE. 12Z MODELS NOT  
BACKING OFF ON INTENSITY AFTER HERMINE MAKES LANDFALL ON NORTH FL  
COAST AROUND MIDNIGHT FRIDAY MORNING. WHILE CONVECTION NOT AS ACTIVE  
AS IT WAS THIS MORNING, LOOKS MUCH STRONGER THAN THIS TIME  
YESTERDAY. STILL SEEING A SLIGHT WEST/NORTH SHIFT AND SLOWER TRACK  
COMPARED WITH PREVIOUS RUNS.  
 
MAIN MESSAGE WE WANT TO SHARE WITH PARTNERS IS EVEN WHEN A STORM  
IS NEARING LANDFALL, DO *NOT* FOCUS ON THE CENTER OF STORM! WIND,  
HEAVY RAIN AND EVEN ISOLATED TORNADO IMPACTS WILL BE FELT QUICKLY  
AND WELL AHEAD OF THE THE CENTER REACHING MIDDLE GA. THIS ONE  
COULD SURPRISE US.  
 
WIND IMPACTS MAY BE SUBSTANTIAL FOR WHAT IS ONLY BEEN JUST NAMED  
A TROPICAL STORM AS STRENGTHENING, OR AT LEAST A LACK OF  
WEAKENING, IS FORECAST EVEN AFTER LANDFALL. WE HAVE NOT SEEN  
TROPICAL STORM FORCE SUSTAINED WINDS IN OVER 10 YEARS IN OUR CWA  
BASED ON OUR INTERNAL RECORDS. SUSTAINED WINDS OF 25 TO 35 MPH  
WITH GUSTS TO 50 MPH MAY BE POSSIBLE AS THE CENTER MOVES INTO OUR  
SOUTHERN AND SOUTHEASTERN COUNTIES. ANOTHER IMPACT IS AN ISOLATED  
TORNADO THREAT LATE THURSDAY NIGHT AND FRIDAY AS THIS AREA IS IN  
FAVORABLE NORTHEAST QUADRANT. SLIGHT RISK AREA IN SPC DAY 2  
OUTLOOK LOOKS GOOD GIVEN CURRENT FORECAST...BUT WOULD NEED TO BE  
ADJUSTED NORTH IF TRACK CHANGES.  
 
FINALLY HEAVY RAIN AND FLASH FLOOD THREAT MAY ALSO BE VERY  
SIGNIFICANT. WARM ADVECTION/WARM FRONT PATTERN EXPECTED TO SETUP  
EAST AND NORTHEAST OF HERMINE, MUCH LIKE A PRE (PREDECESSOR RAINFALL  
EVENT), WHERE HEAVY RAIN DEVELOPS ALONG AND NORTH OF WARM FRONT LIKE  
FEATURE. MODELS DIFFER ON WHERE THIS PRE BAND OF HEAVY RAIN WILL SET  
UP EXACTLY BUT EXPECT HEAVY RAIN TO DEVELOP THURSDAY NIGHT AND  
CONTINUE FRIDAY AS CENTER TRACKS OVER SOUTH INTO EAST GA. AT THIS  
TIME...EXPECTING 3 TO 5 INCHES OF RAIN THRU SAT MORNING MAINLY  
EAST OF LEXINGTON TO MACON TO CORDELE LINE. FLASH FLOOD WATCH HAS  
BEEN ISSUED BUT MAY NEED TO BE ADJUSTED BASED ON TRACK OF STORM.  
 
ANOTHER SET OF GRID UPDATES WILL BE DONE AROUND 5PM AFTER THE NEW  
NHC PACKAGE COMES IN. BASED ON THIS MAY NEED A TROPICAL STORM  
WATCH SHORTLY AFTER.  
 
THE REMAINDER OF THE EXTENDED FORECAST SHOULD BE FAIRLY QUIET AS  
HIGH PRESSURE SETTLES ACROSS THE EAST HALF OF THE COUNTRY. TEMPS  
SHOULD BE A LITTLE BIT COOLER AND THE AIRMASS A BIT DRIER BEHIND  
HERMINE. TEMPS MAY END UP DROPPING BELOW 70 DEGREES OVERNIGHT  
SATURDAY NIGHT/SUNDAY MORNING...BREAKING THE CURRENT STREAK.  
 
NLISTEMAA/BDL/SNELSON  
 
AVIATION...  
00Z UPDATE...  
SHOWER ACTIVITY AT 00Z CONFINED MAINLY TO THE NORTH AND SE OF THE  
TAF SITES. EXPECT CLEARING SKIES OVERNIGHT ACROSS NORTHERN  
SITES...WITH SOME PESKY LOW AND MID LEVEL DECKS ACROSS CSG AND  
MCN. POTENTIAL EXISTS FOR MVFR CONDITIONS AROUND SUNRISE FOR CSG  
AND MCN AS TROPICAL MOISTURE INCREASES. BETWEEN TS HERMINE PUSHING  
TOWARDS THE FL COAST AND A COLD FRONT APPROACHING FROM THE  
NW ON THURS...SHOWER AND CONVECTIVE ACTIVITY LOOKS MORE LIKELY AT  
ALL SITES IN THE AFTERNOON AND EVENING. HAVE PLACED PROB30 AT ATL  
TO COVERT THIS. WINDS WILL PERHAPS BE THE TRICKIEST PART OF THE  
FORECAST. HAVE ELECTED TO KEEP A SOUTHERLY COMPONENT AT ALL  
SITES...WITH DIRECTION FLIRTING BETWEEN SW AND SE THE NEXT 24  
HOURS. WIND SPEEDS 5-10KTS. WILL SEE A DRAMATIC CHANGE IN WINDS  
AND CEILINGS THURSDAY NIGHT INTO FRIDAY AS TS HERMINE CREEPS IN.  
 
//ATL CONFIDENCE...00Z UPDATE...  
MEDIUM ON MVFR DEVELOPMENT...LOW ON WIND DIRECTION...HIGH ALL  
OTHER ELEMENTS.  
 
KOVACIK  
 

 
 
   
PRELIMINARY POINT TEMPS/POPS
 
 
ATHENS 71 92 72 79 / 10 30 50 60  
ATLANTA 73 91 72 83 / 10 30 40 50  
BLAIRSVILLE 65 86 66 77 / 20 30 40 50  
CARTERSVILLE 70 92 71 84 / 20 30 30 40  
COLUMBUS 73 91 74 85 / 20 50 50 60  
GAINESVILLE 71 90 70 79 / 20 30 40 50  
MACON 72 91 73 81 / 20 50 60 60  
ROME 70 92 71 86 / 20 30 30 40  
PEACHTREE CITY 70 91 72 83 / 10 40 40 50  
VIDALIA 73 90 74 83 / 30 50 80 80  
 

 
   
FFC WATCHES/WARNINGS/ADVISORIES
 
 
FLASH FLOOD WATCH FROM LATE THURSDAY NIGHT THROUGH SATURDAY  
MORNING FOR THE FOLLOWING ZONES: BALDWIN...BIBB...BLECKLEY...  
CRISP...DODGE...DOOLY...EMANUEL...GLASCOCK...GREENE...HANCOCK...  
HOUSTON...JEFFERSON...JOHNSON...JONES...LAURENS...MONTGOMERY...  
OGLETHORPE...PULASKI...PUTNAM...TALIAFERRO...TELFAIR...TOOMBS...  
TREUTLEN...TWIGGS...WARREN...WASHINGTON...WHEELER...WILCOX...  
WILKES...WILKINSON.  
 
TROPICAL STORM WATCH FOR THE FOLLOWING ZONES: BLECKLEY...CRISP...  
DODGE...DOOLY...EMANUEL...GLASCOCK...HOUSTON...JEFFERSON...  
JOHNSON...LAURENS...MACON...MONTGOMERY...PEACH...PULASKI...  
SCHLEY...SUMTER...TELFAIR...TOOMBS...TREUTLEN...TWIGGS...  
WASHINGTON...WHEELER...WILCOX...WILKINSON.  
 

 
 

 
 
SHORT TERM...KOVACIK  
LONG TERM....39  
AVIATION...KOVACIK  
 
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