Special Weather Statement, NWS Atlanta, GA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PEACHTREE CITY GA
308 PM EDT FRI AUG 24 2012

.SHORT TERM /TONIGHT THROUGH SATURDAY NIGHT/...
CURRENT RADAR LOOP SHOWS SOME SCATTERED SHOWERS WITH ISOLATED
THUNDERSTORMS ACROSS NORTH AND CENTRAL GA THIS AFTERNOON. THESE
SHOWERS SHOULD CONTINUE THROUGH THIS EVENING AND DISSIPATE SHORTLY
AFTER SUNSET. THE CURRENT MODELS SHOW THE HIGH PRESSURE RIDGE
BUILDING DOWN THE EASTERN SEABOARD KEEPING GA IN A SEMI DRY SLOT
THROUGH THE WEEKEND. WITH THE UPPER LEVEL LOW...NOW OVER THE
CAROLINAS MOVING NE...IT ALSO PUTS GA IN DRYING NWLY UPPER LEVEL
FLOW FOR THE WEEKEND. THIS WILL ALSO HELP TO KEEP PRECIPITATION AT A
MINIMUM. THE RIDGE DOES DO A GOOD JOB NOT ALLOWING THE FRONTAL
BOUNDARY...NOW JUST EAST OF THE ROCKY MOUNTAINS...FROM MOVING TO FAR
EAST THROUGH SUNDAY. THE FRONT MAKES IT AS FAR AS THE MID TO UPPER
MS RIVER VALLEY BEFORE SLOWING ITS EASTERLY PROGRESSION. THERE IS
STILL THE ISSUE OF SOME UPSLOPE FLOW ACROSS THE NORTH GA MOUNTAINS
CREATING SOME ISOLATED SHOWERS SAT/SUN AFTERNOON BUT THAT SHOULD BE
ABOUT IT. PUT IN 20 POPS ACROSS THE NE GA MOUNTAINS SAT BUT WILL
KEEP AND EYE OUT FOR SUN. TEMPS SHOULD REMAIN NEAR SEASONAL NORMS
WITH LOWS IN THE MID TO UPPER 60S AND HIGHS IN THE 80S TO NEAR 90.

01

.LONG TERM /SUNDAY THROUGH FRIDAY/...
LONG TERM FORECAST STILL DOMINATED BY THE TRACK OF TS ISSAC. 12Z
GFS TRACK HAS SHIFTED SLIGHTLY TO THE EAST AND IS SLIGHTLY FASTER
THAN THE PREVIOUS RUN. THE 00Z ECMWF DIFFERS FROM THE GFS AFTER 72
HOURS...PULLING ISSAC MORE TO THE WEST. HAVE STUCK CLOSELY WITH
THE NHC FORECAST TRACK...TENDING TOWARDS A BLEND OF THE EXTENDED
MODELS. BEYOND DAY 6...CHALLENGING FORECAST WITH THE GFS QUICKLY
LIFTING THE LOW OUT OVER THE CAROLINAS...AND THE EURO KEEPING A
SLOWER ISSAC OVER AL. AS A RESULT OF THE LARGE UNCERTAINTY...HAVE
TRIED TO KEEP AT LEAST GOOD CHANCE POPS IN THROUGH THE REMAINDER
OF THE SHORT TERM.

HAVE UPDATED WIND AND POPS THROUGH THE EXTENDED AS NEEDED BASED ON
NEW NHC TRACK AND NEIGHBORING OFFICES. BASED ON OFFICIAL
TRACK...DO HAVE 20-30 KT SUSTAINED WINDS IN THE FAR SW CWA
BEGINNING VERY EARLY WEDNESDAY MORNING...WITH WIND GUSTS TO 35-45
KTS THROUGH DAYBREAK WEDNESDAY. UNCERTAINTY ASSOCIATED WITH
INTENSITY AND LOCATION OF THE SYSTEM HAS RESULTED IN A CAP OF HIGHEST
WIND SPEEDS TO 25KTS OR LESS BEYOND WEDNESDAY. THIS WILL BE
UPDATED AS NHC EXTENDS THEIR FORECAST.

BIG CONCERN...IN ADDITION TO ISOLATED TORNADOES AND HIGH
WINDS...WILL BE FLOODING ASSOCIATED WITH HEAVIEST RAINFALL
AMOUNTS. BASED ON THE CURRENT FORECAST TRACK...WIDESPREAD AMOUNTS
OF 4 TO 8 INCHES CAN BE EXPECTED. AGAIN...DUE TO THE UNCERTAINTY
WITH THE TRACK FOR TUESDAY AND WEDNESDAY...HAVE KEPT RAINFALL
AMOUNTS GENERALLY IN THE 2-4 INCH RANGE IN OUR FORECAST.

PREVIOUS FORECAST DISCUSSION STILL GENERALLY APPLICABLE...AND HAVE
INCLUDED IT BELOW.

31

/ISSUED 535 AM EDT FRI AUG 24 2012/
MAIN FORECAST CONCERN CONTINUES TO BE POTENTIAL IMPACT FROM TS
ISAAC MAINLY FROM TUESDAY THROUGH THURSDAY. LATEST ECMWF SOLUTION
HAS COME INTO MUCH BETTER AGREEMENT WITH THE GFS IN THE
TIMING...INTENSITY...AND POSITIONING OF ISAAC. THE SOLUTIONS ARE
NEARLY IDENTICAL UP UNTIL PROJECTED LANDFALL TUESDAY EVENING NEAR
THE ALABAMA COASTLINE AND WESTERN FL PANHANDLE. THIS ALSO MATCHES
UP WELL WITH THE LATEST OFFICIAL TRACK FORECAST FROM NHC. WITH
SUCH A TRACK EXPOSING THE SYSTEM TO THE WARM GOM SEA SFC...THERE
MAY BE PLENTY OF FUEL AVAILABLE FOR INTENSIFICATION OF THE STORM
PRIOR TO LANDFALL AS IT IS CURRENTLY FORECAST TO STRENGTHEN TO
HURRICANE STATUS OVER THE GULF BY MONDAY. GUIDANCE SUGGESTS THE NW
TRACK SHOULD TURN MORE NORTHWARD AFTER LANDFALL AS IT STEERS
CLOCKWISE AROUND THE WESTERN ATLANTIC UPPER HIGH. THIS BRINGS THE
CENTER OF CIRCULATION NORTHWARD ACROSS ALABAMA INTO THE TN VALLEY.
WHILE THE STRONGEST INLAND WIND IMPACT MAY STAY WEST OF
GEORGIA...THE FORECAST AREA WOULD BE LOCATED IN THE RIGHT FRONT
QUADRANT OF THE STORM FOR MUCH OF THE PERIOD. SUCH A LOCATION
WOULD NOT ONLY ALLOW ASSOCIATED RAINBANDS TO BRING HEAVY TROPICAL
RAINFALL TO THE AREA BUT ALSO POSES THE THREAT FOR EMBEDDED
THUNDERSTORMS AND TORNADOES. THIS SYSTEM WILL CONTINUE TO BE
CLOSELY MONITORED AND FORECAST UPDATES WILL BE MADE WITH THE
LATEST GUIDANCE OR CHANGES IN PROJECTED TRACK AND INTENSITY.

ALL CONSIDERED HAVE INCLUDED MEDIUM TO HIGH END CHANCE POPS
MAINLY ACROSS SOUTHERN PORTIONS MONDAY INTO TUESDAY AND SHIFT THE
HIGHER POPS TOWARD THE WEST AND NORTH PORTIONS WEDNESDAY INTO
THURSDAY. IF GUIDANCE STAYS CONSISTENT...THEN WILL PROBABLY RAISE
POPS IN FUTURE UPDATES TO AT LEAST LIKELY. ALSO...WHILE CURRENT
QPF VALUES ARE AROUND 1 INCH MAINLY ACROSS THE WEST PORTION
TUESDAY NIGHT INTO WEDNESDAY...THERE IS THE POTENTIAL FOR HEAVIER
AMOUNTS AND ADJUSTMENTS WILL BE MADE IF NECESSARY.

FOR TEMPS...GENERALLY STUCK NEAR MEX GUIDANCE BUT RAISED MIN TEMPS A
BIT AS THEY LOOKED TOO COOL. INCREASE IN CLOUD COVERAGE WOULD ALSO
LIKELY KEEP THE DIURNAL RANGE DOWN A BIT AS WELL.

BAKER

&&

.AVIATION...
18Z UPDATE...
CURRENT RADAR LOOP SHOWS SOME ISOLATED SHOWERS ACROSS THE AREA BUT
NONE OF THEM ARE AFFECTING ANY OF THE TAF SITES YET. THESE SHOWERS
WILL CONTINUE WITH SOME THUNDERSTORMS THROUGH LATER THIS EVENING
BEFORE DISSIPATING. CEILINGS WILL STAY VFR EXCEPT IN AND AROUND
TSRA DEVELOPMENT. WINDS WILL CONTINUE OUT OF THE EAST TO
SOUTHEAST IN THE 5-10KT RANGE THROUGH THE PERIOD WITH NO
RESTRICTIONS TO VSBYS EXPECTED.

//ATL CONFIDENCE...18Z UPDATE...
CONFIDENCE IS MEDIUM TO HIGH ON ALL ELEMENTS.

01

&&

.PRELIMINARY POINT TEMPS/POPS...
ATHENS          64  89  65  87 /  20   5   5   5
ATLANTA         68  87  67  87 /  20   5   5  10
BLAIRSVILLE     58  84  60  83 /  20  20   5  20
CARTERSVILLE    62  88  62  87 /  20  10   5  10
COLUMBUS        68  90  66  88 /  20   5   5  10
GAINESVILLE     66  86  67  85 /  20  10   5  10
MACON           65  90  64  88 /  20   5   5  10
ROME            63  90  63  89 /  10  10   5  10
PEACHTREE CITY  62  87  61  86 /  20   5   5  10
VIDALIA         67  89  66  89 /  20   5   5  20

&&

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

SHORT TERM...01
LONG TERM....31
AVIATION...01

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE PEACHTREE CITY GA
621 AM EDT FRI AUG 24 2012

GAZ001>009-011>016-019>025-027-030>039-041>062-066>076-078>086-
089>098-102>113-251030-
BALDWIN-BANKS-BARROW-BARTOW-BIBB-BLECKLEY-BUTTS-CARROLL-CATOOSA-
CHATTAHOOCHEE-CHATTOOGA-CHEROKEE-CLARKE-CLAYTON-COBB-COWETA-
CRAWFORD-CRISP-DADE-DAWSON-DEKALB-DODGE-DOOLY-DOUGLAS-EMANUEL-
FANNIN-FAYETTE-FLOYD-FORSYTH-GILMER-GLASCOCK-GORDON-GREENE-
GWINNETT-HALL-HANCOCK-HARALSON-HARRIS-HEARD-HENRY-HOUSTON-JACKSON-
JASPER-JEFFERSON-JOHNSON-JONES-LAMAR-LAURENS-LUMPKIN-MACON-
MADISON-MARION-MERIWETHER-MONROE-MONTGOMERY-MORGAN-MURRAY-
MUSCOGEE-NEWTON-NORTH FULTON-OCONEE-OGLETHORPE-PAULDING-PEACH-
PICKENS-PIKE-POLK-PULASKI-PUTNAM-ROCKDALE-SCHLEY-SOUTH FULTON-
SPALDING-STEWART-SUMTER-TALBOT-TALIAFERRO-TAYLOR-TELFAIR-TOOMBS-
TOWNS-TREUTLEN-TROUP-TWIGGS-UNION-UPSON-WALKER-WALTON-WARREN-
WASHINGTON-WEBSTER-WHEELER-WHITE-WHITFIELD-WILCOX-WILKES-
WILKINSON-
621 AM EDT FRI AUG 24 2012

THIS HAZARDOUS WEATHER OUTLOOK IS FOR NORTH AND CENTRAL GEORGIA.

.DAY ONE...TODAY AND TONIGHT...
ISOLATED THUNDERSTORMS POSSIBLE ACROSS NORTH AND CENTRAL GEORGIA
THROUGH THIS EVENING.

.SYNOPSIS...
WHILE A TROUGH OF LOW PRESSURE SHIFTS EAST OF THE AREA
TODAY...LINGERING MOISTURE WILL STILL ALLOW FOR A SLIGHT CHANCE OF
ISOLATED CONVECTIVE DEVELOPMENT.

.PRIMARY HAZARDS...
THE PRIMARY HAZARDS FROM ANY THUNDERSTORMS WILL BE GUSTY
WINDS...OCCASIONAL LIGHTNING...AND HEAVY RAINFALL.

.DISCUSSION...
LINGERING MOISTURE AND DAYTIME HEATING WILL RESULT IN RATHER
MODEST CAPE VALUES UP TO 1000-1500 J/KG ACROSS PORTIONS OF THE
AREA AND ALLOW FOR ISOLATED THUNDERSTORM POTENTIAL THROUGH THIS
EVENING.

.DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY...
THERE IS A SLIGHT CHANCE OF THUNDERSTORMS THROUGH MONDAY. THERE IS
AN INCREASED CHANCE OF THUNDERSTORMS FOR TUESDAY THROUGH THURSDAY
AS THE IMPACTS FROM ISAAC BEGIN TO REACH THE AREA. ALTHOUGH THERE
IS STILL UNCERTAINTY IN THE FORECAST...THE CURRENT FORECAST TRACK
WOULD BRING THE CHANCE OF FLOODING AND GUSTY WINDS TO THE AREA.
ISOLATED TORNADOES MAY ALSO BE POSSIBLE WITH ANY STRONG STORMS
EMBEDDED IN THE RAINBANDS ASSOCIATED WITH THE TROPICAL SYSTEM.
THOSE IN NORTH AND CENTRAL GEORGIA NEED TO CONTINUE TO CLOSELY
MONITOR THE FORECAST FOR ISAAC.

.SPOTTER INFORMATION STATEMENT...
SPOTTER ACTIVATION WILL NOT BE NEEDED THROUGH TONIGHT.

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE PEACHTREE CITY GA
409 PM EDT FRI AUG 24 2012

GAZ008-242045-
409 PM EDT FRI AUG 24 2012

...SIGNIFICANT WEATHER ADVISORY FOR 40 MPH WINDS IN UNION COUNTY
UNTIL 445 PM EDT...

AT 404 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
STRONG THUNDERSTORM 7 MILES NORTHEAST OF JONES CREEK...MOVING
SOUTHWEST AT 5 MPH.

WIND GUSTS OF 40 MPH ARE LIKELY AS THIS STORM MOVES ACROSS UNION
COUNTY THROUGH 445 PM EDT. SOME LOCATIONS IN THE PATH OF THE STORM
INCLUDE JONES CREEK.

THESE WIND GUSTS MAY PRODUCE MINOR DAMAGE TO TREE LIMBS AND BLOW
LIGHT...UNSECURED OBJECTS AROUND.

&&

LAT...LON 3496 8404 3492 8396 3480 8407 3487 8412
      3489 8411 3491 8412 3492 8415
TIME...MOT...LOC 2009Z 073DEG 4KT 3493 8403

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE PEACHTREE CITY GA
446 PM EDT FRI AUG 24 2012

GAZ008-242115-
446 PM EDT FRI AUG 24 2012

...SIGNIFICANT WEATHER ADVISORY FOR 40 MPH WINDS IN UNION COUNTY
UNTIL 515 PM EDT...

AT 441 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
STRONG THUNDERSTORM OVER JONES CREEK...MOVING SOUTHWEST AT 5 MPH.

THIS STORM HAS THE POTENTIAL TO PRODUCE PEA SIZED HAIL...FREQUENT
CLOUD TO GROUND LIGHTNING AND WIND GUSTS TO 40 MPH AS IT MOVES ACROSS
UNION COUNTY THROUGH 515 PM EDT. SOME LOCATIONS IN THE PATH OF THIS
STORM INCLUDE JONES CREEK AND GADDISTOWN. HEAVY DOWNPOURS WILL CAUSE
PONDING OF WATER ON ROADWAYS.

&&

LAT...LON 3489 8399 3468 8403 3471 8411 3473 8410
      3480 8410 3480 8413 3481 8414 3485 8414
      3488 8411 3489 8411 3491 8407
TIME...MOT...LOC 2046Z 026DEG 5KT 3487 8407

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE PEACHTREE CITY GA
450 PM EDT FRI AUG 24 2012

GAZ006-242115-
450 PM EDT FRI AUG 24 2012

...SIGNIFICANT WEATHER ADVISORY FOR 40 MPH WINDS IN FANNIN COUNTY
UNTIL 515 PM EDT...

AT 446 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
STRONG THUNDERSTORM NEAR HEMP...MOVING SOUTHWEST AT 5 MPH.

THIS STORM HAS THE POTENTIAL TO PRODUCE PEA SIZED HAIL...FREQUENT
CLOUD TO GROUND LIGHTNING AND WIND GUSTS TO 40 MPH AS IT MOVES ACROSS
FANNIN COUNTY THROUGH 515 PM EDT. SOME LOCATIONS IN THE PATH OF THIS
STORM INCLUDE HEMP...MARGRET AND HURST. HEAVY DOWNPOURS WILL CAUSE
PONDING OF WATER ON ROADWAYS.

SIGNIFICANT WEATHER ADVISORIES ARE ISSUED FOR WINDS UP TO 50 MPH...
HAIL LESS THAN THE SIZE OF QUARTERS...OR SIGNIFICANT CLOUD-TO-GROUND
LIGHTNING.

&&

LAT...LON 3491 8412 3489 8411 3488 8411 3485 8414
      3481 8414 3480 8413 3480 8410 3477 8410
      3474 8418 3487 8424 3492 8415
TIME...MOT...LOC 2050Z 070DEG 15KT 3486 8412