Special Weather Statement, NWS Atlanta, GA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PEACHTREE CITY GA
152 PM EDT MON JUN 27 2011

.PREV DISCUSSION... /ISSUED 1135 AM EDT MON JUN 27 2011/

UPDATE...
SCATTERED SHOWERS WITH ISOLATED THUNDERSTORM OVER PORTIONS OF
CENTRAL GEORGIA THIS MORNING...MOVING SLOWLY SOUTH. SHORT TERM AND
CONVECTIVE MODELS SHOWING REDEVELOPMENT OVER AREAS SOUTH OF
ATLANTA TO ATHENS THIS AFTERNOON. MCS NORTH OF AREA APPEARS TO BE
SLOWING...WITH RUC HOLDING CONVECTION NORTH OF AREA THROUGH 00Z.
HAVE ADJUSTED POPS AND WEATHER GRIDS TO SHOW LATEST THINKING.
CONVECTION AND CLODS OVER CENTRAL GEORGIA HAVE ALSO IMPACTED
TEMPERATURES THAT AREA AND HAVE ADJUSTED HOURLY/MAX TEMPERATURES
ACCORDINGLY. LATEST UPDATES WILL BE ISSUED SHORTLY.

PREV DISCUSSION... /ISSUED 741 AM EDT MON JUN 27 2011/
SHORT TERM /TODAY THROUGH WEDNESDAY/...
BIGGEST CHALLENGE WITH TODAYS FORECAST IS THE TRAJECTORY OF THE
MCS NOW MOVING THROUGH IA/MO/IL. NONE OF THE MODELS PICK UP THAT
THE MCS EXISTS WHICH IS WHAT IS MAKING THIS A DIFFICULT FORECAST.
IT APPEARS THAT THE SOUTHEAST MOVING MCS IS FOLLOWING THE THERMAL
WIND VECTOR WHICH OVER THE NEXT 18 HOURS WOULD KEEP IT MOVING
SOUTHEAST. THE INHIBITING FACTOR IS THE BUILDING RIDGE OVER THE
SOUTHERN THIRD OF THE COUNTRY. ANOTHER INHIBITING FACTOR IS THAT
OUR ATMOSPHERE GOT WORKED OVER VERY WELL SUNDAY AFTERNOON AND
EVENING. ALL MODELS HAVE CAPES INCREASING TO OVER 2000 THIS
AFTERNOON. HAVING SAID ALL OF THIS...MAV AND MET POPS ARE
GENERALLY LESS THAN 10 PERCENT. SEEING THAT THE MODELS HAVE NOT
PICKED UP ON THE MCS...WILL THROW OUT GUIDANCE POPS AND CONTINUE
WITH SLIGHT CHANCE TO CHANCE POPS THIS MORNING AND CHANCE POPS
THIS AFTERNOON WITH ISOLATED SEVERE POSSIBLE.

TUESDAY IS A DIFFERENT STORY. MODELS HAVE A COLD FRONT MOVING ACROSS
THE CWA TUESDAY AFTERNOON AND EVENING. GIVEN THE VOLATILITY OF THE
CURRENT STATE OF THE ATMOSPHERE...FEEL HIGH CHANCE POPS ARE IN
ORDER FOR TUESDAY AFTERNOON AND EVENING. MET GUIDANCE SEEMS TO HAVE
A BETTER HANDLE ON THIS THAN THE MAV GUIDANCE. DRIER AIR MOVES INTO
THE CWA WEDNESDAY WHICH SHOULD LIMIT CONVECTION IN THE AFTERNOON TO
SLIGHT CHANCE.

LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
BOTH THE GFS AND ECMWF ARE IN GOOD AGREEMENT THROUGH THE LONG TERM
FOR THE FIRST PART OF THE LONG TERM WITH DIFFERENCES DEVELOPING
TOWARD THE WEEKEND. A LARGE H5 RIDGE BUILDS OVER THE CENTRAL US.
THIS RIDGE WILL FLATTEN AS IT SHIFTS INTO THE EASTERN U.S. DURING
THIS TIME THE CWA WILL BE IN A WEAK UPPER FLOW. THE ONLY THING
KICKING OFF THUNDERSTORMS WILL BE DAYTIME HEATING AND OUTFLOW
BOUNDARIES...IN OTHER WORDS BACK TO CLIMO BY THE WEEKEND WITH
ISOLATED TO SCATTERED AFTERNOON AND EVENING THUNDERSTORMS.

&&

.AVIATION...
18Z UPDATE...
VFR AT ALL TAF SITES THROUGH THE FORECAST PERIOD...BUT TSRA IS
EXPECTED TO LOWER SITES TO AT LEAST MVFR. SOME TSRA COULD BRING
WINDS GUSTING UP TO 35KT. TSRA THREAT SHOULD DIMINISH AT ALL SITES
BY 03Z AS FORECASTED LINE MOVES THROUGH...WITH CONVECTION START UP
TOMORROW AFTER 14Z. WINDS EXPECTED TO STAY WESTERLY.

//ATL CONFIDENCE...18Z UPDATE...
HIGH CONFIDENCE ON WINDS AND CIGS.
MEDIUM CONFIDENCE ON VSBYS.
LOW CONFIDENCE ON TIMING OF TSRA.
PREFERRED NAM BUFR AND HRRR GUIDANCE OVER GFS BUFR.

10

&&

.PRELIMINARY POINT TEMPS/POPS...
ATHENS          95  71  94  72 /  50  30  50  30
ATLANTA         93  73  92  74 /  50  30  50  30
BLAIRSVILLE     85  66  85  67 /  50  30  50  30
CARTERSVILLE    93  68  92  69 /  50  30  50  30
COLUMBUS        96  73  95  74 /  40  40  50  50
GAINESVILLE     90  71  91  72 /  50  30  50  30
MACON           97  71  95  72 /  40  50  50  50
ROME            92  71  92  70 /  50  30  50  30
PEACHTREE CITY  93  70  93  70 /  40  30  50  50
VIDALIA         94  73  95  74 /  40  50  50  50

&&

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

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE PEACHTREE CITY GA
1119 AM EDT MON JUN 27 2011

GAZ001>009-011>016-019>025-027-030>039-041>062-066>076-078>086-
089>098-102>113-281530-
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-
1119 AM EDT MON JUN 27 2011

THIS HAZARDOUS WEATHER OUTLOOK IS FOR NORTH AND CENTRAL GEORGIA.

.DAY ONE...THIS AFTERNOON AND TONIGHT
SCATTERED THUNDERSTORMS AND ISOLATED SEVERE THUNDERSTORMS EXPECTED
TODAY AND TONIGHT.

.SYNOPSIS...
A COMPLEX OF THUNDERSTORMS OVER NORTHERN MISSOURI AND CENTRAL ILLINOIS
WILL CONTINUE MOVING SOUTHEAST THROUGH TONIGHT. THESE
THUNDERSTORMS ARE EXPECTED TO MOVE INTO NORTH GEORGIA THIS
AFTERNOON.

.PRIMARY HAZARDS...
THE PRIMARY HAZARD FROM ISOLATED SEVERE THUNDERSTORMS WILL BE
FREQUENT CLOUD TO GROUND LIGHTNING AND GUSTY WINDS TO 60 MPH. THE
BEST LOCATION FOR ISOLATED SEVERE STORMS WILL BE ACROSS NORTH
AND CENTRAL GEORGIA THIS AFTERNOON AND TONIGHT.

.DISCUSSION...
A COMPLEX OF THUNDERSTORMS OVER NORTHERN MISSOURI AND CENTRAL ILLINOIS
WILL CONTINUE MOVING SOUTHEAST THROUGH TONIGHT. INSTABILITY
INDICES ARE EXPECTED TO BE STRONG TODAY WITH CAPES GETTING INTO
THE 2000-3000 RANGE AND LIFTED INDICES AROUND -4 TO -5 ACROSS GEORGIA.
THERE IS AN UPPER LEVEL RIDGE BUILDING IN ACROSS THE SOUTHERN
STATES WHICH WILL HELP CAP THE ATMOSPHERE BUT IT DOES NOT LOOK
STRONG ENOUGH TO KEEP ISOLATED SEVERE STORMS FROM DEVELOPING.

.DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY
ISOLATED TO SCATTERED THUNDERSTORMS EXPECTED EACH DAY.

.SPOTTER INFORMATION STATEMENT...
SPOTTERS ACTIVATION IS NOT REQUESTED BUT SPOTTERS ARE ENCOURAGED
TO SUBMIT REPORTS OF SEVERE WEATHER THROUGH THE WEB BY GOING TO
WEATHER.GOV/ATLANTA.

10

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE PEACHTREE CITY GA
215 PM EDT MON JUN 27 2011

GAZ044-054-055-271845-
215 PM EDT MON JUN 27 2011

...SIGNIFICANT WEATHER ADVISORY FOR PEA SIZED HAIL AND 40 MPH WINDS
IN FAYETTE...CLAYTON AND FULTON COUNTIES UNTIL 245 PM EDT...

AT 212 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
STRONG THUNDERSTORM OVER COLLEGE PARK...MOVING SOUTHEAST AT 10 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
FAYETTE...CLAYTON AND FULTON COUNTIES THROUGH 245 PM EDT. SOME
LOCATIONS IN THE PATH OF THIS STORM INCLUDE UNION CITY...FAIRBURN...
EAST POINT...COLLEGE PARK...HAPEVILLE...HARTSFIELD-JACKSON AIRPORT...
FOREST PARK...RIVERDALE...KENWOOD...FORT GILLEM...LAKE CITY...
MORROW...JONESBORO AND FAYETTEVILLE.

BRIEF HEAVY DOWNPOURS WILL CAUSE PONDING OF WATER ON ROADWAYS.

&&

LAT...LON 3364 8464 3372 8450 3367 8438 3359 8428
      3337 8448
TIME...MOT...LOC 1814Z 311DEG 10KT 3361 8449

16

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SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE PEACHTREE CITY GA
251 PM EDT MON JUN 27 2011

GAZ056-057-271915-
251 PM EDT MON JUN 27 2011

...SIGNIFICANT WEATHER ADVISORY FOR PEA SIZED HAIL AND 40 MPH WINDS
IN SPALDING AND HENRY COUNTIES UNTIL 315 PM EDT...

AT 248 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
STRONG THUNDERSTORM OVER SUNNY SIDE...MOVING SOUTHEAST AT 15 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
SPALDING AND HENRY COUNTIES THROUGH 315 PM EDT. SOME LOCATIONS IN THE
PATH OF THIS STORM INCLUDE BIRDIE...VAUGHN...SUNNY SIDE...ATLANTA
MOTOR SPEEDWAY...HAMPTON...LUELLA...HIGHLAND MILLS...TOWALAGA...
EXPERIMENT...WALKER MILL...ROVER...GRIFFIN AND ORCHARD HILL. BRIEF
HEAVY DOWNPOURS WILL CAUSE PONDING OF WATER ON ROADWAYS.

&&

LAT...LON 3329 8442 3332 8438 3335 8439 3336 8435
      3341 8436 3343 8432 3343 8430 3345 8429
      3345 8428 3328 8409 3325 8412 3318 8413
      3319 8433 3327 8440
TIME...MOT...LOC 1851Z 322DEG 15KT 3332 8430

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE PEACHTREE CITY GA
342 PM EDT MON JUN 27 2011

GAZ066-067-272015-
342 PM EDT MON JUN 27 2011

...SIGNIFICANT WEATHER ADVISORY FOR DIME SIZED HAIL AND 40 MPH WINDS
IN TROUP AND MERIWETHER COUNTIES UNTIL 415 PM EDT...

AT 339 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
STRONG THUNDERSTORM OVER STOVALL...MOVING SOUTH AT 10 MPH.

THIS STORM HAS THE POTENTIAL TO PRODUCE DIME SIZED HAIL...FREQUENT
CLOUD TO GROUND LIGHTNING AND WIND GUSTS TO 40 MPH AS IT MOVES ACROSS
TROUP AND MERIWETHER COUNTIES THROUGH 415 PM EDT. SOME LOCATIONS IN
THE PATH OF THIS STORM INCLUDE ODESSADALE...BIG SPRINGS...
MOUNTVILLE...STOVALL AND DURAND. BRIEF HEAVY DOWNPOURS WILL CAUSE
PONDING OF WATER ON ROADWAYS.

&&

LAT...LON 3306 8495 3305 8476 3287 8471 3287 8497
      3288 8499
TIME...MOT...LOC 1942Z 006DEG 8KT 3296 8486

16