Special Weather Statement, NWS Atlanta, GA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PEACHTREE CITY GA
325 PM EDT FRI JUL 20 2012

.SHORT TERM /TONIGHT THROUGH SATURDAY NIGHT/...
CONVECTIVE COVERAGE AND RESULTING POPS THROUGH THE SHORT TERM
FORECAST ARE A BIT OF A PUZZLE. IT IS BEGINNING TO LOOK LIKE THE
HRRR HAD THE CORRECT FORECAST FOR THE REST OF TODAY...WITH RESPECT
TO HOLDING OFF ON CONVECTION MOVING INTO NORTH GEORGIA UNTIL LATER
IN THE AFTERNOON. HOWEVER...CONVECTION HAS REALLY STARTED FIRING IN
THE CAROLINAS. CAPES HAVE JUMPED TO OVER 1500 J/KG EVERYWHERE...AND
OVER 2500 J/KG ACROSS A LARGE PORTION OF THE CWA...SO IT SHOULD BE
JUST A MATTER OF TIME BEFORE CONVECTION STARTS POPPING ACROSS
GEORGIA. ISOLATED SEVERE THUNDERSTORMS REMAIN A POSSIBILITY WITH
DAMAGING WINDS AND LOCALLY HEAVY RAIN THE MAIN THREAT. WILL CONTINUE
OVERALL LIKELY POPS...BUT WILL BACK OFF FOR EARLY THIS AFTERNOON
TRENDING UPWARD TOWARD 00Z. ALL OF THIS IS IN RESPONSE TO AN UPPER
TROUGH SITUATED OVER THE APPALACHIANS...WITH WEAK SURFACE FRONT
CURRENTLY ANALYZED ACROSS TENNESSEE INTO MISSISSIPPI. THE STRENGTH
OF THE TROUGH IS FORECAST TO DEEPEN THROUGH THE SHORT TERM...WITH
GENERAL SOUTHWEST FLOW THROUGH THE COLUMN. MOISTURE LEVELS WILL
REMAIN HIGH /PWS NEAR OR JUST ABOVE 2 INCHES BOTH THIS AFTERNOON AND
SATURDAY/. EXPECT NUMEROUS THUNDERSTORMS AGAIN ON SATURDAY BUT
PERHAPS WITH SLIGHTLY LESS COVERAGE. SPC CURRENTLY JUST HAS THE AREA
IN SEE TEXT FOR DAY2 SO WILL MONITOR SEVERE POTENTIAL AS WE GET
CLOSER. THE WEAK COLD FRONT WILL SLOWLY SAG SOUTH THROUGH THE
WEEKEND BUT WILL HELP TO FOCUS CONVECTION THAT WILL CONTINUE IN A
GENERAL DIURNAL TREND.

FOR TEMPS...MET IS MUCH COOLER FOR SATURDAY HIGHS THAN THE MAV BUT
OVERALL HAVE TRIED TO TAKE A BIAS-ADJUSTED BLEND ESPECIALLY
CONSIDERING THE UNKNOWNS AS FAR AS CONVECTION SPECIFICS GO.

TDP

.LONG TERM /SUNDAY THROUGH FRIDAY/...
NO MAJOR CHANGES TO THE LONG TERM...
BDL

A DECENT AMOUNT OF MOISTURE OVER THE AREA THROUGH MONDAY
AFTERNOON BEFORE DIMINISHING UNDER THE BUILDING RIDGE. SHOULD
CONTINUE TO SEE A MOSTLY DIURNAL CONVECTIVE TREND IN THE EXTENDED
AS MOISTURE FROM THE GULF ROTATES UP INTO THE AREA UNDER THE
SURFACE RIDGE THROUGH FRIDAY. EVEN WITH THE HIGH IN PLACE...PLENTY
OF LOW LEVEL MOISTURE WILL SUPPORT DIURNAL CONVECTION EACH DAY.
FORECAST PRECIPITABLE WATER VALUES STILL SHOWING NEAR 2.0 INCH
VALUES THROUGH THE MIDDLE OF NEXT WEEK...AND WITH K-INDEX VALUES
IN THE MID TO UPPER 30S...HEAVY RAIN STILL REMAINS A THREAT.
WIDESPREAD 1-1.25 INCHES ARE EXPECTED THROUGH SUNDAY
AFTERNOON...WITH LOCALLY HEAVIER AMOUNTS ASSOCIATED WITH AREAS OF
MODERATE TO STRONG CONVECTION. BY WEDNESDAY...LOW PRESSURE
DEEPENING OVER THE CANADIAN MARITIMES WILL DRAG ANOTHER FRONTAL
BOUNDARY THROUGH THE MID ATLANTIC STATES...WITH TROUGH EXTENDING
INTO NORTH GEORGIA. THE MODELS DO DIFFER A BIT ON JUST HOW FAR
SOUTH THIS FRONTAL BOUNDARY MOVES SO WILL CONTINUE WITH DIURNALLY
DRIVEN CHANCE POPS THROUGH FRIDAY.

01

&&

.AVIATION... 18Z UPDATE...
EXPECT CONVECTION TO DEVELOP LATER THIS AFTERNOON AND EVENING...
AND HAVE KEPT TREND WITH TEMPO IN THE TAFS. ONCE THE CONVECTION
CLEARS...SHOULD SEE ANOTHER ROUND OF MVFR VSBY AND IFR CIGS
SATURDAY MORNING MUCH LIKE THIS MORNING WAS. SOME UNCERTAINTY AS
TO WHEN AND HOW FAST THE CIGS WILL LIFT. ANOTHER ROUND OF
CONVECTION EXPECTED FOR SATURDAY AFTERNOON. SOUTHWEST WINDS
GENERALLY 5-10KT THROUGH THE PERIOD EXCEPT IN THUNDERSTORMS.

//ATL CONFIDENCE...18Z UPDATE...
HIGH ON CONVECTION TODAY AND SATURDAY AFTERNOON...MEDIUM ON
IMPACTS TO ATL.
HIGH ON DEVELOPMENT OF IFR CIGS...MEDIUM ON TIMING OF ONSET AND
LIFTING.
HIGH ON WINDS AND VSBY.

TDP

&&

.PRELIMINARY POINT TEMPS/POPS...
ATHENS          70  87  70  90 /  60  60  40  30
ATLANTA         71  86  71  88 /  60  60  40  40
BLAIRSVILLE     67  82  66  82 /  60  60  40  50
CARTERSVILLE    71  85  70  88 /  60  60  30  60
COLUMBUS        72  88  72  92 /  50  70  30  30
GAINESVILLE     71  84  70  87 /  60  60  40  50
MACON           73  88  70  93 /  50  70  30  30
ROME            71  86  71  90 /  60  60  30  60
PEACHTREE CITY  71  85  69  88 /  60  70  40  30
VIDALIA         73  92  75  94 /  40  50  30  30

&&

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

SHORT TERM...TDP
LONG TERM....BDL
AVIATION...TDP

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE PEACHTREE CITY GA
900 AM EDT FRI JUL 20 2012

GAZ001>009-011>016-019>025-027-030>039-041>062-066>076-078>086-
089>098-102>113-211000-
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-
900 AM EDT FRI JUL 20 2012

THIS HAZARDOUS WEATHER OUTLOOK IS FOR NORTH AND CENTRAL GEORGIA.

.DAY ONE...THIS AFTERNOON AND TONIGHT...
ISOLATED SEVERE THUNDERSTORMS EXPECTED THIS AFTERNOON AND EVENING.

.SYNOPSIS...
A WEAK FRONTAL BOUNDARY WILL MOVE TO NORTH GEORGIA THROUGH TONIGHT
AS HIGH PRESSURE CONTINUES ACROSS FLORIDA AND THE GULF OF MEXICO.

.PRIMARY HAZARDS...
THE PRIMARY HAZARDS WILL BE HEAVY RAIN WITH LOCALIZED FLOODING...
DAMAGING WINDS...FREQUENT LIGHTNING...AND POSSIBLY LARGE HAIL. THE
MOST LIKELY TIME FOR SEVERE THUNDERSTORMS WILL BE THIS AFTERNOON AND
EVENING. NUMEROUS THUNDERSTORMS CAN ALSO BE EXPECTED DURING THE DAY.

.DISCUSSION...
ABUNDANT MOISTURE WILL BE IN PLACE TODAY WITH CAPES INCREASING TO
3000 AND LIFTED INDICES OF -4 TO -5. AN UPPER LEVEL TROUGH ALONG THE
APPALACHIANS WILL AID THUNDERSTORM DEVELOPMENT GIVING WAY TO
NUMEROUS THUNDERSTORMS AND ISOLATED SEVERE STORMS.

.DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY...
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.

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE PEACHTREE CITY GA
534 PM EDT FRI JUL 20 2012

GAZ020-021-202200-
534 PM EDT FRI JUL 20 2012

...SIGNIFICANT WEATHER ADVISORY FOR PEA SIZED HAIL AND 40 MPH WINDS
IN BARTOW AND CHEROKEE COUNTIES UNTIL 600 PM EDT...

AT 531 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
STRONG THUNDERSTORM NEAR FUNKHOUSER...MOVING EAST 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
BARTOW AND CHEROKEE COUNTIES THROUGH 600 PM EDT. SOME LOCATIONS IN
THE PATH OF THIS STORM INCLUDE WHITE...PINE LOG...FUNKHOUSER...LAKE
ARROWHEAD...SALACOA VALLEY AND WALESKA. HEAVY DOWNPOURS WILL CAUSE
PONDING OF WATER ON ROADWAYS.

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

&&

LAT...LON 3441 8459 3438 8458 3438 8445 3439 8443
      3437 8440 3438 8439 3424 8438 3426 8476
      3440 8476 3440 8474 3442 8473
TIME...MOT...LOC 2134Z 269DEG 14KT 3435 8465

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE PEACHTREE CITY GA
618 PM EDT FRI JUL 20 2012

GAZ002-003-202245-
618 PM EDT FRI JUL 20 2012

...SIGNIFICANT WEATHER ADVISORY FOR PEA SIZED HAIL AND 40 MPH WINDS
IN WALKER AND CATOOSA COUNTIES UNTIL 645 PM EDT...

AT 614 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
STRONG THUNDERSTORM NEAR CHICKAMAUGA...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
WALKER AND CATOOSA COUNTIES THROUGH 645 PM EDT. SOME LOCATIONS IN THE
PATH OF THIS STORM INCLUDE FORT OGLETHORPE...LAKEVIEW...
CHICKAMAUGA...CHATTANOOGA VALLEY...FAIRVIEW...BOYNTON...BLUE
SPRING...WOOD STATION...BEAUMONT...RINGGOLD...ROCK SPRING AND NOBLE.
HEAVY DOWNPOURS WILL CAUSE PONDING OF WATER ON ROADWAYS.

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

&&

LAT...LON 3490 8502 3487 8504 3486 8506 3482 8508
      3482 8513 3477 8514 3473 8517 3472 8515
      3470 8516 3486 8543 3499 8533 3499 8525
TIME...MOT...LOC 2218Z 301DEG 8KT 3489 8528