Area Forecast Discussion
Issued by NWS Atlanta, GA

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FXUS62 KFFC 290051
AFDFFC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PEACHTREE CITY GA
851 PM EDT FRI AUG 28 2015

.UPDATE...
PREVIOUS CONVECTION IN THE SW TIER OF THE CWA HAS HAD DIMINISHING
TREND SUPPORTED BY CONSENSUS OF HI-RES MODELS. WILL CONTINUE WITH
ONLY SLIGHT POPS FOR MUCH OF OVERNIGHT IN FAR SOUTH...THOUGH STILL
LOOK LIKE CHANCE FOR SOME SHOWER ENHANCEMENT NEAR SUNRISE STARTING
TO ADVECT NORTHWARD AS WEAK UPPER LOW STARTS TO DRAW IN GREATER
GULF MOISTURE. AFOREMENTIONED CONVECTION THIS EVENING HAS RESULTED
IN DECENTLY LOWER TEMPS FOR PARTS OF THE SW...THOUGH DO NOT THINK
WILL HAVE MUCH IMPACT IN OVERNIGHT MINS...SO HAVE THEREFORE ONLY ADJUSTED
THE EVENING TRENDS BASED ON OBSERVED TEMPS AND DWPTS. PREVIOUS
DISCUSSION FOLLOWS...

BAKER

&&

.PREV DISCUSSION... /ISSUED 807 PM EDT FRI AUG 28 2015/

.SHORT TERM /TONIGHT THROUGH SATURDAY NIGHT/...

MOISTURE WILL CONTINUE TO INCREASE DURING THE SHORT TERM WITH A
SUSTAINED DEEP EAST TO SOUTHEAST FLOW...AND THE AIR MASS BECOMING
MORE UNSTABLE. THE MORNING OVERCAST HAS FINALLY DIMINISHED...BUT
SHOWERS AND A FEW THUNDERSTORMS WERE DEVELOPING ACROSS THE CENTRAL
SECTIONS OF THE AREA. EXPECT NORTH GA TO REMAIN DRY TONIGHT...BUT
WILL KEEP A CHANCE OR SLIGHT CHANCE OVER PORTIONS OF CENTRAL. UPPER
LOW REMAINS TO OUR WEST THROUGH THE PERIOD AND A COUPLE OF SHORT
WAVES MOVING ACROSS THE NORTHERN GULF WILL BRING A SURGE OF MOISTURE
NORTHWARD INTO THE FORECAST AREA LATE TONIGHT AND SATURDAY. LIKELY
POPS SPREADING INTO MUCH OF THE FORECAST AREA ON SATURDAY STILL LOOK
OKAY. HAVE STAYED CLOSE TO MAV/MET TEMPERATURES.

41

&&

.LONG TERM /SUNDAY THROUGH FRIDAY/...

STILL QUITE A BIT OF UNCERTAINTY THROUGH THE MAJORITY OF THE EXTENDED
FORECAST PERIOD. MODELS ARE NOT HANDLING ERIKA IN ANYTHING RESEMBLING
A CONSISTENT MANNER. RECENT TRENDS HAVE BEEN A MORE WESTERLY PATH
WITH JUST ABOUT ALL OF THE MEDIUM RANGE MODELS...HOWEVER THERE
CONTINUES TO BE A FAIR AMOUNT OF SPREAD CONCERNING THE PATH AND
SIGNIFICANTLY MORE SPREAD WITH RESPECT TO THE STRENGTH OF WHATEVER
REMAINS OF HER AFTER SHE SHREDS THROUGH ISLANDS AND INTO THE VICINITY
OF THE FLORIDA PENINSULA. FOR NOW I HAVE CHOSEN TO NOT MAKE TOO MANY
CHANGES TO THE EARLIER EXTENDED FORECAST GRIDS TO AVOID ANY YOYOING
OF THE FORECAST...BUT WE REMAIN IN FAIRLY GOOD AGREEMENT WITH OUR
NEIGHBORING OFFICES CONCERNING THE BASIC FORECAST GRIDS.

PLEASE SEE THE PREVIOUS LONG TERM FORECAST DISCUSSION BELOW.

20

PREV LONG TERM DISCUSSION... /ISSUED 325 AM EDT FRI AUG 28 2015/

/SATURDAY NIGHT THROUGH THURSDAY/...

PROBABLY THE ONLY ASPECT OF THE LONG TERM PORTION WITH ANY CONFIDENCE
AT ALL IS THE INITIAL TIME PERIOD BEGINNING SUNDAY. EVEN THEN...SOME
UNCERTAINTY AS DEEP LAYER MOISTURE VALUES APPEAR LOWER THAN MODEL
RUNS FROM THIS TIME LAST NIGHT. THIS IS ESPECIALLY TRUE OVER NE GA
WHERE PRECIPITABLE WATER VALUES ARE ONLY AROUND 1.25 INCHES ACCORDING
TO THE GFS. THIS TRANSITIONS QUICKLY TO HIGHER VALUES FOR THE
SOUTHERN TIER WITH 1.75 IN FOR THE MACON AREA BUT STILL ONLY SLIGHTLY
HIGHER THAN CLIMO. WILL STILL BE DEALING WITH UPPER LOW WHICH LOOKS
TO OPEN UP AND TRANSLATE EAST OVER NORTH GA LATE SUNDAY. THIS SHOULD
AID IN THE DEVELOPMENT OF THUNDERSTORMS...PERHAPS HIGHER COVERAGE
THAN THE MOISTURE PROFILES WOULD SUGGEST. WILL CARRY HIGH END CHANCE
POPS FOR SOUTHERN SECTIONS AND KEEP IN MID RANGE CHANCE FOR REMAINING
SECTIONS.

FORECAST BECOMES A BIT MORE PROBLEMATIC AT THIS POINT AS OPERATIONAL
GUIDANCE DIVERGES FROM SOME OF THE TROPICAL GUIDANCE MODELS AND THE
OFFICIAL TRACK. SOME OF THE ENSEMBLE MEMBERS OF THE GFS INCLUDING THE
OPERATIONAL BRING THE SYSTEM ACROSS THE GULF AND THEN NORTHWARD INTO
GEORGIA. THIS WOULD BE IN STARK CONTRAST TO CURRENT FORECAST WHICH
KEEPS HIGHEST POPS OVER THE EASTERN TIER OF GA AND MAY EVEN INCLUDE
SUBSIDENCE FOR OUR WESTERN SECTIONS. PLAN IS TO TAKE A LOOK 06Z
GUIDANCE ON ERIKA AND TWEAK CURRENT FORECAST TO BETTER MATCH ITS
SOLUTIONS. WILL THEN AWAIT OFFICIAL GUIDANCE AND TWEAK POP GRIDS
FURTHER BASED ON THIS INFORMATION.

SO IN GENERAL...THE SOLUTIONS REALLY RUN THE SPECTRUM ON THIS ONE AND
COULD INCLUDE A SUBSIDENCE SOLUTION IN WHICH WE ARE LARGELY
UNAFFECTED WITH LITTLE RAINFALL TO ONE N WHICH SIGNIFICANT MOISTURE
MOVES IN A REMAINS CREATING A FLOODING SCENARIO FOR MUCH OF THE AREA.
AGAIN...WILL MENTION UNCERTAINTY IN HWO FOR THE EXTENDED BUT
CERTAINLY IN NO POSITION AT THIS POINT TO OFFER ANY DETAILS FOR EARLY
NEXT WEEK.

DEESE

&&

.AVIATION...
00Z UPDATE...
INITIAL VFR CIGS SHOULD LOWER TO IFR BETWEEN 06Z AND 09Z TONIGHT
THEN GRADUALLY IMPROVE TO MVFR AFTER 14Z...THOUGH MAY STRUGGLE TO
GET INTO VFR TOMORROW AFTERNOON AS SHRA CHANCES INCREASE. MVFR
VSBYS POSSIBLE IN EARLY MORNING AND WITH ANY PRECIP. HELD OFF ON
TSRA MENTION SATURDAY DUE TO UNCERTAINTY IN BEST TIMING AND HOW
LATE CIGS HAVE BEEN ABLE TO SCATTER THE LAST SEVERAL DAYS. WINDS
STAYING ESE GENERALLY 7-10 KTS NEAR KATL WITH SOME LOWER
MAGNITUDES AT OTHER SITES.

//ATL CONFIDENCE...00Z UPDATE...
MEDIUM TO LOW ON TSRA CHANCE/TIMING.
HIGH ON ALL ELSE.

BAKER

&&

.PRELIMINARY POINT TEMPS/POPS...
ATHENS          68  86  70  84 /  10  50  40  40
ATLANTA         71  85  70  84 /  10  60  50  40
BLAIRSVILLE     62  81  64  78 /  10  50  30  50
CARTERSVILLE    68  85  68  84 /  10  60  50  40
COLUMBUS        72  86  71  87 /  40  70  60  40
GAINESVILLE     68  83  70  81 /  10  50  40  40
MACON           71  87  71  87 /  30  60  60  50
ROME            69  85  69  84 /  10  60  50  50
PEACHTREE CITY  70  85  69  84 /  20  60  50  40
VIDALIA         72  89  73  88 /  40  60  60  60

&&

.FFC WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM...41/BAKER
LONG TERM....20
AVIATION...BAKER


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