Special Weather Statement, NWS Atlanta, GA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PEACHTREE CITY GA
335 PM EDT TUE JUL 26 2011

.SHORT TERM /TONIGHT THROUGH THURSDAY NIGHT/...
LATEST ANALYSIS SHOWS FRONTAL BOUNDARY SITUATED ACROSS CENTRAL
GEORGIA...AS IT CONTINUES TO DRIFT SOUTHWARD THIS EVENING. THIS
BOUNDARY HAS PROVIDED A FOCUS FOR AFTERNOON SHOWER AND THUNDERSTORM
DEVELOPMENT...NOW MAINLY SOUTH AND EAST OF THE CWA. MODERATE
INSTABILITIES REMAIN ACROSS NORTH GEORGIA...AND WITH AFTERNOON CU
FIELD ALLOWING FOR SOME ADDITIONAL DIURNAL HEATING...A FEW ISOLATED
THUNDERSTORMS HAVE DEVELOPED BEHIND THE BOUNDARY ACROSS NORTH
GEORGIA. A FEW OF THE HI RES SHORT TERM MODELS ARE INDICATING
SUSTAINED ACTIVITY TO CONTINUE WELL INTO THE EVENING HOURS...SO HAVE
CONTINUED WITH A POP GRADIENT OF SLIGHT CHANCE TO CATEGORICAL FROM
NW TO SE CWA THROUGH 00Z...AND THEN DIMINISH TO LIKELY POPS
OVERNIGHT.

SURFACE HIGH PRESSURE IN PLACE THROUGH THE SHORT TERM...SUPPORTED BY
RIDGE ALOFT. MODELS FAIRLY CONSISTENT WITH INDICATING UPPER LEVEL
DISTURBANCE ALONG THE CAROLINA COAST DRIFTING WESTWARD THROUGH
THURSDAY NIGHT. MODELS VARY ON TRACK...WITH THE GFS SHOWING THE AREA
OF HEIGHTENED VORTICITY MOVING INTO NORTH GEORGIA BY LATE
THURSDAY...WHILE ECMWF AND NAM KEEP THE DISTURBANCE ALONG THE
GEORGIA COAST AND INTO SOUTH GEORGIA BY THURSDAY AFTERNOON.
REGARDLESS...FLOW FROM BOTH THE ATLANTIC AND GULF OF MEXICO WILL
KEEP AMPLE LOW LEVEL MOISTURE IN PLACE THROUGH THE SHORT TERM...SO
HAVE KEPT SLIGHT CHANCE TO CHANCE POPS IN THE FORECAST. WITH PWS
NEARING THE 99TH PERCENTILE FOR NORTH AND CENTRAL GEORGIA...TROPICAL
AIR MASS REMAINS IN PLACE...AND CAN EXPECT CONVECTION TO BE
ACCOMPANIED BY LOW VISIBILITIES AND PERIODS OF HEAVY RAIN. MODELS
SUGGEST INSTABILITIES TO REMAIN THE HIGHEST OUTSIDE OF THE CWA
THROUGH THE FORECAST PERIOD...SO HAVE INDICATED ON SLIGHT CHANCE
TSTMS ASSOCIATED WITH THE POPS.

HIGH PRESSURE RIDGE CONTINUES TO KEEP TEMPERATURES SLIGHTLY WARMER
THAN NORMAL ACROSS MUCH OF THE AREA...AND 850 MB TEMPERATURES
APPROACH 20 TO 21 DEGREES C ON WEDNESDAY. PRECIP ACTIVITY AND GOOD
CLOUD COVER WILL KEEP MORE MILD TEMPERATURES ACROSS CENTRAL AND
SOUTH GEORGIA. BY THURSDAY...REDUCED 850 MB TEMPERATURES...INCREASED
CLOUD COVER AND PRECIP ACTIVITY ACROSS NORTH AND WESTERN GEORGIA ARE
EXPECTED TO BRING SLIGHTLY COOLER TEMPERATURES TO THE AREA. IN
GENERAL...SIDED WITH JUST COOLER THAN MAV MET BLEND FOR THURSDAY
HIGHS.

31/WH

.LONG TERM /FRIDAY THROUGH TUESDAY/...
OVERALL...DIURNALLY DRIVEN CONVECTION EXPECTED TO CONTINUE INTO THE
LONG TERM...WITH INFLUENCE OF THE NEXT FRONTAL BOUNDARY FELT ACROSS
NORTH GEORGIA BY FRIDAY AFTERNOON...AND THEN ANOTHER SUNDAY AND AND
INTO MONDAY. GFS SEEMS TO BE A LITTLE SLOWER WITH THE SECOND FRONTAL
BOUNDARY THAN THE ECMWF...BUT DUE TO THE UNCERTAINTY ASSOCIATED WITH
THE TIMING OF THIS NEXT SYSTEM...HAVE PERSISTED WITH THE PREVIOUS
FORECAST AND SIDED WITH THE ECMWF. HAVE CONTINUED WITH SLIGHT CHANCE
TO CHANCE POPS THROUGH THE EXTENDED PERIOD TO ACCOUNT FOR THE IMPACT
OF THE FRONTS AS THEY MOVE THROUGH THE REGION. TEMPERATURES EXPECTED
TO REMAIN WARM THROUGH THE PERIOD...WITH HIGHS IN THE 90S...AND LOWS
IN THE 70S. WILL NEED TO CONTINUE TO MONITOR MODELED AND FORECAST
CONDITIONS INTO THE WEEKEND FOR POSSIBLE HEAT ADVISORY.

31/WH

&&

.AVIATION...
18Z UPDATE...
SURFACE BOUNDARY ACROSS THE AREA WILL KEEP MOST CONVECTION SOUTH
OF THE METRO AREA THIS AFTERNOON...BUT HAVE STILL KEPT CB IN THE
CLOUD GROUP FOR NORTHERN TAFS FOR ISOLATED CONVECTION. WINDS THIS
EVENING SHOULD STAY NORTHWEST EXCEPT AHN...SUBSIDING OVERNIGHT.
EXPECT MVFR VSBYS TO DEVELOP WEDNESDAY MORNING...WITH POSSIBLE
ISOLATED IFR ESPECIALLY AT MCN AND CSG. MAY SEE BRIEF LOW CIGS...
BUT AT NORTHERN TAFS EXPECT LOW CLOUDS TO REMAIN SCT OR FEW. WINDS
SHIFTING TO THE EAST 14-15Z WEDNESDAY.

//ATL CONFIDENCE...18Z UPDATE...
MEDIUM TO HIGH ON VSBY AND CIGS.
MEDIUM ON TIMING OF WIND SHIFT WEDNESDAY.
MEDIUM ON OCCURRENCE OF CONVECTION...LOW ON IMPACTS TO ATL.

TDP

&&

.PRELIMINARY POINT TEMPS/POPS...
ATHENS          71  97  72  93 /  20  20  10  20
ATLANTA         74  95  74  90 /  20  20  10  20
BLAIRSVILLE     62  90  65  91 /  20  20  10  20
CARTERSVILLE    69  96  70  93 /  10  10  10  20
COLUMBUS        75  93  75  92 /  30  40  20  50
GAINESVILLE     72  95  73  91 /  20  10  10  20
MACON           73  94  74  93 /  30  30  20  20
ROME            69  97  72  94 /  10  10  10  30
PEACHTREE CITY  69  94  72  90 /  20  20  10  20
VIDALIA         73  88  76  93 /  60  50  20  20

&&

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

31/TDP/WH

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE PEACHTREE CITY GA
342 AM EDT TUE JUL 26 2011

GAZ001>009-011>016-019>025-027-030>039-041>062-066>076-078>086-
089>098-102>113-271100-
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-
342 AM EDT TUE JUL 26 2011

THIS HAZARDOUS WEATHER OUTLOOK IS FOR NORTH AND CENTRAL GEORGIA.

.DAY ONE...TODAY AND TONIGHT
SCATTERED TO NUMEROUS THUNDERSTORMS ARE EXPECTED TODAY...ESPECIALLY
ACROSS CENTRAL GEORGIA.

.SYNOPSIS...
A WEAK SURFACE TROUGH OF LOW PRESSURE WILL MEANDER ACROSS PARTS OF
NORTH AND CENTRAL GEORGIA TODAY.

.PRIMARY HAZARDS...
THE PRIMARY HAZARDS FROM THUNDERSTORMS WILL BE OCCASIONAL CLOUD TO
GROUND LIGHTNING...LOCALLY HEAVY RAIN AND WIND GUSTS TO 35 MPH. THE
GREATER CHANCE FOR THUNDERSTORM DEVELOPMENT WILL BE GENERALLY SOUTH
OF CARROLLTON TO ATHENS LINE...AND ALTHOUGH CONVECTIVE ACTIVITY
CAN OCCUR AT ANYTIME TODAY... THE GREATER CHANCE FOR THUNDERSTORMS
WILL BE BETWEEN NOON AND 10 PM.

.DISCUSSION...
AN ACTIVE NORTHWEST FLOW ALOFT WILL INTERACT WITH A MOIST AND MODERATELY
UNSTABLE AIR MASS TO PRODUCE SCATTERED TO NUMEROUS SHOWERS AND THUNDERSTORMS
ACROSS PARTS OF NORTH AND MOST OF CENTRAL GEORGIA TODAY. AS CAPE VALUES
INCREASE INTO THE 2000 TO 2500 RANGE LATER THIS AFTERNOON...A FEW
THUNDERSTORMS COULD BECOME STRONG. HOWEVER... TODAY'S THUNDERSTORMS
ARE EXPECTED TO STAY BELOW SEVERE LIMITS. THE SLOW MOVING STORMS COMBINED
WITH OVER TWO INCH PRECIPITABLE WATERS WILL LIKELY PRODUCE LOCALLY
HEAVY RAIN AT TIMES... POSSIBLY RESULTING IN THE BRIEF PONDING OF WATER
ACROSS A FEW LOW LYING...FLOOD PRONE AREAS.

.DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH MONDAY
THERE IS A CHANCE OF THUNDERSTORMS EACH DAY...MAINLY DURING THE AFTERNOON
AND EVENING.

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

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE PEACHTREE CITY GA
334 PM EDT TUE JUL 26 2011

GAZ074-262015-
334 PM EDT TUE JUL 26 2011

...SIGNIFICANT WEATHER ADVISORY FOR FREQUENT LIGHTNING IN WASHINGTON
COUNTY UNTIL 415 PM EDT...

AT 329 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
STRONG THUNDERSTORM OVER WARTHEN...MOVING SOUTH AT 10 MPH.

THIS STORM HAS THE POTENTIAL TO PRODUCE SIZED HAIL...FREQUENT CLOUD
TO GROUND LIGHTNING AND WIND GUSTS TO 35 MPH AS IT MOVES ACROSS
WASHINGTON COUNTY THROUGH 415 PM EDT. SOME LOCATIONS IN THE PATH OF
THIS STORM INCLUDE HAMBURG STATE PARK...WARTHEN...DOWNS...TENNILLE
AND SANDERSVILLE. BRIEF HEAVY DOWNPOURS WILL CAUSE PONDING OF WATER
ON ROADWAYS.

LIGHTNING DETECTION SYSTEMS INDICATE NUMEROUS CLOUD-TO-GROUND
LIGHTNING STRIKES ACROSS WASHINGTON COUNTY...INCLUDING AREAS AROUND
HAMBURG STATE PARK...WARTHEN...DOWNS...TENNILLE AND SANDERSVILLE.
RESIDENTS IN THIS AREA SHOULD STAY INDOORS. ELECTRICAL APPLIANCES AND
TELEPHONES SHOULD NOT BE USED UNLESS IN AN EMERGENCY.

&&

LAT...LON 3287 8269 3294 8298 3320 8284 3323 8279
      3321 8274 3318 8274 3313 8267 3310 8264
TIME...MOT...LOC 1934Z 017DEG 8KT 3312 8275

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE PEACHTREE CITY GA
420 PM EDT TUE JUL 26 2011

GAZ074-262045-
420 PM EDT TUE JUL 26 2011

...SIGNIFICANT WEATHER ADVISORY FOR FREQUENT CLOUD-TO-GROUND
LIGHTNING IN WASHINGTON COUNTY UNTIL 445 PM EDT...

AT 415 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
STRONG THUNDERSTORM OVER TENNILLE...MOVING SOUTH AT 20 MPH.

FREQUENT CLOUD-TO-GROUND LIGHTNING IS OCCURRING WITH THESE
THUNDERSTORMS. MOVE INDOORS IMMEDIATELY! LIGHTNING IS ONE OF NATURES
NUMBER ONE KILLERS. REMEMBER...IF YOU CAN HEAR THUNDER...YOU ARE
CLOSE ENOUGH TO BE STRUCK BY LIGHTNING. RESIDENTS IN THE AREA SHOULD
REMAIN INDOORS AND AWAY FROM ELECTRICAL APPLIANCES...DOORS...AND
WINDOWS UNTIL THE STORMS HAVE PASSED. LAND-LINE TELEPHONES SHOULD
ONLY BE USED IN AN EMERGENCY.

&&

LAT...LON 3277 8276 3280 8278 3281 8282 3276 8295
      3277 8296 3280 8296 3282 8297 3283 8297
      3286 8299 3303 8293 3300 8272
TIME...MOT...LOC 2020Z 012DEG 19KT 3292 8285

19