Special Weather Statement, NWS Atlanta, GA

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE PEACHTREE CITY GA
200 AM EDT THU MAY 26 2011

.UPDATE...
LINE OF THUNDERSTORMS DEVELOPED ACROSS LOUISIANA/ARKANSAS THIS
AFTERNOON AND HAS PUSHED INTO MISSISSIPPI. CURRENTLY TORNADO
WATCHES WEST OF HERE FOR A PORTION OF THE LINE. HRRR AND GFS SHOW
THAT THE SYSTEM WILL WEAKEN AS IT CONTINUES TO MOVE EASTWARD.
BASED ON THIS THOUGHT THAT THE SYSTEM WILL WEAKEN AS IT
APPROACHES... CONTINUED THE GENERAL TREND IN THE FORECAST. MADE
MINOR ADJUSTMENTS TO POPS TONIGHT TO CUT BACK ON POPS ACROSS
NORTHEAST GEORGIA AND CONFINE THE POPS TO NORTHWEST GEORGIA IN THE
9-12Z RANGE. BEST CHANCE OF SHOWERS AND THUNDERSTORMS WILL BE
AFTER 12Z AND THE BEST CHANCE OF SEVERE STORMS STILL APPEARS TO BE
ACROSS NORTH GEORGIA IN THE AFTERNOON AND EVENING AS THE LINE
STRENGTHENS. AROUND 25-30KTS OF 0-1 KM SHEAR AND 2000-2500 J/KG
MUCAPE AT THAT TIME. THAT BEING SAID...LARGE HAIL...DAMAGING WINDS
AND ISOLATED TORNADOES WILL BE POSSIBLE.

FORECAST TEMPS WERE 8-10 DEGREES TOO COOL ACROSS NORTHEAST GEORGIA
SO ADJUSTED HOURLY AND MIN TEMPS FOR THIS.

11

&&

.PREV DISCUSSION... /ISSUED 730 PM EDT WED MAY 25 2011/

..SEVERE STORMS LIKELY THURSDAY...

SHORT TERM /TONIGHT THROUGH FRIDAY NIGHT/...

LATEST MSAS ANALYSIS SHOWS HIGH PRESSURE REMAINS ANCHORED OFFSHORE
THE SOUTHEAST COAST WITH RIDGING THROUGH THE FLORIDA PENINSULA.
WITH STRONG LOW PRESSURE OVER THE MISSOURI VALLEY...A RESULTANT
SOUTH TO SOUTHWEST FLOW HAS DEVELOPED LOCALLY. THIS HAS ALLOWED
FOR AN INCREASE IN MOISTURE WITH DEWPOINTS PUSHING INTO THE LOWER
60S ALONG WITH VERY WARM TEMPS WITH MID 90S VALUES EXPECTED TO THE
SOUTH. ALTHOUGH MIN RH VALUES MAY END UP BEING A LITTLE LOWER THAN
MODELS HAD INDICATED...STILL FEEL WE WILL REMAIN AT OR ABOVE
CRITERIA FOR FIRE WEATHER CONCERNS THIS AFTERNOON AND EVENING.

FIRST WX SYSTEM OF INTEREST IN QUITE SOME TIME REMAINS TO OUR WEST
FOR THE INITIAL PORTION OF THE FORECAST WITH WIDESPREAD SEVERE
WEATHER EVENT ONGOING OVER THE TENNESSEE VALLEY AND INTO THE
NORTHERN MISSISSIPPI VALLEY. BIG QUESTION INITIALLY WILL BE HOW
FAR AND QUICKLY THIS ACTIVITY TRANSLATES EASTWARD DURING THE
OVERNIGHT PERIOD. MODELS CURRENTLY SHOW HIGH INSTABILITY SHIFTING
INTO NORTHERN ALABAMA AND SOUTHERN TENNESSEE BY 00Z THIS EVENING
WITH SQUALL LINE LIKELY MAINTAINING A GOOD PORTION OF ITS
INTENSITY. MODELS IN AGREEMENT HOWEVER...THAT WITH THE LOSS OF
HEATING...INSTABILITY WILL DROP OFF MARKEDLY THROUGH 06Z AS SQUALL
LINE LOSES INTENSITY AND MOMENTUM TOWARD THE AREA. FEEL THIS MAY
BE TOO ABRUPT AN END TO CONVECTION FOR THE NORTHWEST CORRIDOR AND
WILL INCLUDE LOW END POPS THROUGH THE OVERNIGHT PERIOD.

BETTER CHANCES ARE IN STORE AS UPPER LOW SHIFTS EASTWARD THROUGH
12Z THU. INITIAL LINE OF CONVECTION WILL DEVELOP OVER THE
NORTHWEST PORTION BUT MODELS INDICATE IT WILL TAKE THE HEATING OF
THE DAY ONCE AGAIN TO REALIZE INSTABILITY SUFFICIENT ENOUGH FOR
ROBUST UPDRAFTS. AS ALLUDED TO BY PREVIOUS FORECASTER...MODELS
SEEM TO BE ON THE UPSWING CONCERNING ASSOCIATED SHEAR VALUES WITH
50 KT JET NOW PROGGED TO SKIRT THE NORTHERN ZONES THU AFTERNOON.
THIS ALONG WITH RELATIVELY HIGH SIG SEVERE AND TOR VALUES WARRANT
SVR INCLUSION IN THE ZONES FOR THE ROUGHLY THE AREA OF THE CURRENT
SPC DAY 2.

CONSIDERABLE DISAGREEMENT FOR THE REMAINDER OF THE SHORT TERM AS
GFS SHUNTS BULK OF THE MOISTURE AND INSTABILITY TO THE EAST WHILE
UPPER RIDGE BUILDS IN QUICKLY FOR FRIDAY AFTERNOON. NAM12 NOT
NEARLY AS EAGER TO DRY THINGS OUT AND GIVEN THE TIME OF YEAR WE
ARE GETTING INTO...PREFER A LESS CLEAN FRONTAL PASSAGE AT THIS
POINT WITH CONTINUED MID RANGE POPS THROUGH FRIDAY AFTERNOON.

LONG TERM /SATURDAY THROUGH WEDNESDAY/...GIVEN THE CONTINUED
DISPARITY BETWEEN THE GFS AND THE ECMWF ON THE PLACEMENT OF MID
LEVEL HIGH THROUGH THE EXTENDED PORTION...CURRENT SLIGHT CHANCE
POPS LOOK ON TARGET AND NO MAJOR CHANGES ARE PLANNED AT THIS TIME.

AVIATION...
06Z UPDATE...
SHOULD BE VFR MOST OF THE NIGHT...BUT MAYBE SOME MVFR CEILINGS
MOVING INTO THE TAF SITES JUST BEFORE SUNRISE. MOISTURE INCREASES
TODAY WITH CIGS DEVELOPING BETWEEN 040-060 AFTER 14Z. THUNDERSTORMS
IN CENTRAL AL LOOK LIKE THEY WILL DISSIPATE BEFORE REACHING THE TAF
SITES THIS MORNING. PRECIP CHANCES INCREASE FROM WEST TO EAST
THIS AFTERNOON WITH THE BEST CHANCES COMING IN AFTER 22Z THU IN
THE ATL/CSG AREAS. WINDS WILL REMAIN SOUTH SOUTHWEST 10 TO 15KT WITH
A FEW GUSTS TONIGHT AHEAD OF THE CONVECTION. CONTINUING THURSDAY
WITH A FEW GUSTS OF 20 TO 25KTS IN THE AFTERNOON.

//ATL CONFIDENCE...
06Z UPDATE...
MEDIUM ON ALL ELEMENTS.

41

&&

.PRELIMINARY POINT TEMPS/POPS...
ATHENS          63  92  64  85 /  10  20  50  30
ATLANTA         66  83  65  82 /   5  30  60  30
BLAIRSVILLE     62  83  57  80 /  10  70  60  30
CARTERSVILLE    62  86  59  84 /  10  50  40  20
COLUMBUS        67  89  67  86 /   5  20  40  30
GAINESVILLE     65  85  64  83 /  10  40  60  40
MACON           65  93  65  87 /   5  20  30  30
ROME            62  89  60  85 /  20  60  30  20
PEACHTREE CITY  60  87  60  84 /   5  20  60  30
VIDALIA         70  92  69  87 /  10  20  30  30

&&

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

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE PEACHTREE CITY GA
645 AM EDT WED MAY 25 2011

GAZ001>009-011>016-019>025-027-030>039-041>062-066>076-078>086-
089>098-102>113-261045-
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-
645 AM EDT WED MAY 25 2011

THIS HAZARDOUS WEATHER OUTLOOK IS FOR NORTH AND CENTRAL GEORGIA.

.DAY ONE...TODAY AND TONIGHT
ISOLATED THUNDERSTORMS ARE POSSIBLE LATE TONIGHT OVER EXTREME
NORTHWEST GEORGIA.

.SYNOPSIS...
HIGH PRESSURE CENTERED OFF THE SOUTHEAST COAST AND LOW PRESSURE
OVER THE MIDWEST WILL KEEP A SOUTHWEST FLOW OF AIR OVER THE REGION
THROUGH TONIGHT.

.PRIMARY HAZARDS...
THE PRIMARY HAZARDS WILL BE CLOUD TO GROUND LIGHTNING...GUSTY
WINDS AND POSSIBLY SMALL HAIL.

.DISCUSSION...
STRONG LOW PRESSURE ALOFT OVER THE MID WEST WILL BEGIN TO MOVE
EASTWARD TODAY. A COUPLE OF DISTURBANCES AHEAD OF THIS LOW WILL
MOVE THROUGH THE TENNESSEE AND OHIO VALLEYS TODAY AND TONIGHT.
WITH A MODERATELY UNSTABLE AIR MASS IN PLACE...ISOLATED
THUNDERSTORMS ARE POSSIBLE OVER FAR NORTHWEST GEORGIA AFTER
MIDNIGHT TONIGHT. THE MAIN AREA FOR THUNDERSTORM DEVELOPMENT WILL
BE ALONG AND NORTH OF A ROME TO DALTON LINE. THUNDERSTORMS SHOULD
REMAIN BELOW SEVERE LIMITS.

.DAYS TWO THROUGH SEVEN...THURSDAY THROUGH TUESDAY
THERE IS A CHANCE OF THUNDERSTORMS EACH DAY EXCEPT ON MONDAY.

.SPOTTER INFORMATION STATEMENT...
SPOTTER ACTIVATION IS NOT EXPECTED THROUGH TONIGHT.

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE PEACHTREE CITY GA
228 AM EDT THU MAY 26 2011

GAZ001>003-011-260715-
228 AM EDT THU MAY 26 2011

...SIGNIFICANT WEATHER ADVISORY FOR 45 MPH WINDS IN WALKER...
CATOOSA...CHATTOOGA AND DADE COUNTIES UNTIL 315 AM EDT...

AT 226 AM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED
STRONG THUNDERSTORMS FROM 20 MILES NORTH OF COLE CITY TO 38 MILES
WEST OF CLOUDLAND...MOVING EAST AT 45 MPH.

WIND GUSTS OF 45 MPH ARE LIKELY AS THESE STORMS MOVE ACROSS WALKER...
CATOOSA...CHATTOOGA AND DADE COUNTIES THROUGH 315 AM EDT. SOME
LOCATIONS IN THE PATH OF THESE STORMS INCLUDE COLE CITY...
STEPHENSVILLE...HOOKER...MORGANVILLE...WILDWOOD...RISING FAWN...
CLOUDLAND CANYON STATE PARK...NEW ENGLAND...TRENTON...CHATTANOOGA
VALLEY...LOOKOUT MOUNTAIN...RISING FAWN...CEDAR GROVE...LAKEVIEW AND
CHICKAMAUGA.

&&

LAT...LON 3499 8498 3491 8502 3488 8501 3486 8506
      3482 8507 3482 8513 3473 8517 3472 8505
      3459 8506 3458 8511 3443 8518 3438 8533
      3428 8539 3428 8544 3429 8546 3498 8561
TIME...MOT...LOC 0627Z 269DEG 43KT 3524 8567 3485 8582
          3450 8614