Special Weather Statement, NWS Atlanta, GA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PEACHTREE CITY GA
406 AM EDT FRI JUL 20 2012

.SHORT TERM /TODAY THROUGH SATURDAY/...
INITIAL CONCERN
IS THE CONVECTIVE COMPLEX (MCS) SPREADING SOUTHWARD FROM TN THIS
MORNING. REGIONAL RADARS...CLOUD TOP TEMPERATURES NOTED ON SATELLITE
AND LIGHTNING DATA ALL SUGGEST THE STRONGER STORMS WILL PUSH INTO
NORTH AL... WITH A WEAKENING TREND NOTED FOR CONVECTION MOVING INTO
NORTH GA. THEREFORE...EXPECT MAINLY SHOWERS TO PUSH ACROSS NORTH GA
THIS MORNING...TO INCLUDE METRO ATLANTA...BEFORE DISSIPATING.
HOWEVER...CANNOT RULE OUT A THUNDERSTORM OR TWO WITH THIS
ACTIVITY...SO WILL MENTION A SLIGHT CHANCE OF THUNDER THROUGH THE
MORNING HOURS. THE GREATER THUNDERSTORM THREAT WILL OCCUR DURING
AFTERNOON HEATING AS AN ACTIVE UPPER TROUGH INTERACTS WITH A MOIST
(NEAR 2 INCH PW'S) AND UNSTABLE AIR MASS (1500-2500 J/KG CAPE) TO
PRODUCE SCATTERED TO NUMEROUS SHOWERS AND THUNDERSTORMS THIS
AFTERNOON AND EVENING. REMNANT OUTFLOW BOUNDARIES FROM THIS
MORNING'S MCS SHOULD HELP PROVIDE A FOCUS FOR STORM DEVELOPMENT...
AND THIS SHOULD OCCUR MAINLY OVER NORTH GA WHERE BOUNDARIES SHOULD
BE LINGERING. A SLIGHT INCREASE IN VERTICAL WIND SHEAR FROM A
STRENGTHENING SW MID LEVEL FLOW AHEAD OF A COLD FRONT PUSHING INTO
TN TODAY COULD AID IN STRONG TO SEVERE STORM DEVELOPMENT...
ESPECIALLY IF ENHANCED BY WEAK DISTURBANCES TRAVERSING THE UPPER
TROUGH TODAY. SPC HAS PLACED NORTH GA IN A SLIGHT RISK TODAY...
MAINLY NORTH OF A HAMILTON TO MONTICELLO TO WASHINGTON LINE. THE
PRIMARY THREAT WILL BE DAMAGING WIND GUSTS... BUT ALSO EXPECT
FREQUENT LIGHTNING...HEAVY RAIN AND SMALL HAIL WITH THE STRONGER
STORMS. ANY SLOW MOVING STORMS WILL PRODUCE LOCALLY HEAVY RAIN...
AND COULD RESULT IN BRIEF LOCALIZED FLASH FLOODING. MODELS AGREE ON
STALLING THE COLD FRONT OVER TN TONIGHT... THEN SAGGING THE FRONT
INTO NORTH GA ON SATURDAY WHERE IT LIKELY LINGERS BEFORE PUSHING
BACK NORTH ON SUNDAY. WILL CONTINUE TO SHOW A SLIGHT CHANCE OF
THUNDER OVERNIGHT... WITH LIKELY POPS WARRANTED AGAIN ON SATURDAY AS
THE ACTIVE UPPER TROUGH INTERACTS WITH THE FRONTAL BOUNDARY.

INCREASING CLOUDS AND CONVECTIVE ACTIVITY SHOULD HOLD DAYTIME HIGHS
DOWN INTO THE 80S FOR MOST AREAS TODAY AND AGAIN ON SATURDAY. HAVE
LEANED TOWARD A MAV AND MET BLEND THROUGH THE SHORT TERM AS MAV
LOOKED A BIT WARM AND MET COOL FOR HIGHS. THE LOWS WERE VERY CLOSE
AND LOOKED REASONABLE.

39

.LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/...
FRONTAL BOUNDARY WHICH SAGS OVER GA SAT WILL BEGIN TO PUSH BACK
NORTHWARD SAT NIGHT AS BERMUDA LIKE RIDGE BUILDS OFF THE GA/CAROLINA
COAST. THE BOUNDARY KEEPS A DECENT AMOUNT OF MOISTURE AND A FOCUSING
MECHANISM 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 DAY 7. 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 DAY 7.

AS FOR TEMPERATURES...THINGS SHOULD BE A BIT COOLER THIS WEEKEND
WITH HI TEMPS IN THE 80S TO LOW 90S DUE TO THE FRONTAL BOUNDARY AND
RAIN. TEMPS WILL BEGIN TO REBOUND MONDAY THROUGH WEDNESDAY WITH
TEMPS BACK INTO THE MID 90S BY WED/THU.

01

&&

AVIATION...
06Z UPDATE...
VFR CONDITIONS ARE EXPECTED TO PREVAIL FOR ATLANTA AREA TAF SITES
THIS MORNING BUT WILL HAVE TO MONITOR THIS CLOSELY AS PATCHY
IFR-MVFR CIGS WILL LIKELY DEVELOP AGAIN THIS MORNING. MAIN CONCERN
IS CONVECTIVE COMPLEX OVER TN AND SPREADING SOUTH. MESO-SCALE MODELS
AND TIMING TOOL INDICATES AT LEAST MID LEVEL CIGS AND SCT -SHRA'S
WILL SPREAD INTO THE ATLANTA AREA AROUND 09-11Z THIS MORNING...
BEFORE DISSIPATING BY 14Z. AN ACTIVE TROUGH ALOFT WILL SUPPORT
AFTERNOON TSTM DEVELOPMENT...WITH BEST TIMING AT ATL AROUND 19-24Z.
MODELS AGREE ON IFR CIGS DEVELOPING EARLY SAT MORNING MOST TAF
SITES. OTHERWISE...A SW WIND AT 6-9KTS WILL PREVAIL TODAY

//ATL CONFIDENCE...06Z UPDATE...
MEDIUM CONFIDENCE ON TIMING OF -SHRA AND DEVELOPMENT OF MORNING
STRATUS. MEDIUM TO HIGH CONFIDENCE ALL OTHER ELEMENTS.

39

&&

.PRELIMINARY POINT TEMPS/POPS...
ATHENS          88  72  84  70 /  70  60  60  40
ATLANTA         88  72  84  70 /  70  60  60  40
BLAIRSVILLE     84  69  82  66 /  70  60  60  40
CARTERSVILLE    89  71  85  70 /  70  60  60  40
COLUMBUS        89  73  88  72 /  70  50  60  30
GAINESVILLE     87  72  85  70 /  70  60  60  40
MACON           90  73  89  71 /  70  50  60  30
ROME            89  72  89  72 /  70  60  50  30
PEACHTREE CITY  88  71  85  70 /  70  60  60  40
VIDALIA         90  73  90  74 /  70  40  60  20

&&

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

SHORT TERM...39
LONG TERM....01
AVIATION...39

HAZARDOUS WEATHER OUTLOOK...UPDATED
NATIONAL WEATHER SERVICE PEACHTREE CITY GA
925 PM EDT THU JUL 19 2012

GAZ001>009-011>016-019>025-027-030>039-041>062-066>076-078>086-
089>098-102>113-200900-
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-
925 PM EDT THU JUL 19 2012

THIS HAZARDOUS WEATHER OUTLOOK IS FOR NORTH AND CENTRAL GEORGIA.

.DAY ONE...TONIGHT...
ISOLATED TO SCATTERED THUNDERSTORMS POSSIBLE...MAINLY THIS EVENING.

.SYNOPSIS...
AN UPPER LEVEL LOW WILL PERSIST OVER SOUTHEAST GEORGIA THROUGH
TONIGHT WITH A WEAK SURFACE TROUGH EXTENDING FROM THE CAROLINAS INTO
CENTRAL GEORGIA.

.PRIMARY HAZARDS...
THE PRIMARY HAZARDS WILL BE HEAVY RAIN...GUSTY WINDS...AND FREQUENT
CLOUD-TO-GROUND LIGHTNING. THE MOST LIKELY TIME FOR THUNDERSTORM
DEVELOPMENT WILL BE BEFORE MIDNIGHT.

.DISCUSSION...
THE ATMOSPHERE ACROSS NORTH AND CENTRAL GEORGIA HAS BEGUN TO
STABILIZE SOME THIS EVENING AS TEMPERATURES COOL...HOWEVER MARGINAL
INSTABILITY REMAINS IN PLACE. ISOLATED TO SCATTERED THUNDERSTORMS
ARE STILL POSSIBLE...MAINLY THIS EVENING. ALTHOUGH THE ATMOSPHERE
WILL CONTINUE TO STABILIZE SOMEWHAT OVERNIGHT..A FEW ISOLATED
THUNDERSTORMS WILL BE POSSIBLE AFTER MIDNIGHT.

.DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY...
NUMEROUS THUNDERSTORMS ARE EXPECTED AGAIN FRIDAY AND SATURDAY...
WITH THE POSSIBILITY OF ISOLATED SEVERE STORMS. SCATTERED
THUNDERSTORMS ARE EXPECTED SUNDAY THROUGH WEDNESDAY. THUNDERSTORM
DEVELOPMENT WILL GENERALLY BE DURING THE AFTERNOON AND EVENING
HOURS.

.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
459 AM EDT FRI JUL 20 2012

GAZ007-013-014-200930-
459 AM EDT FRI JUL 20 2012

...SIGNIFICANT WEATHER ADVISORY FOR FREQUENT LIGHTNING AND 40 MPH
WINDS IN PICKENS...DAWSON AND GILMER COUNTIES UNTIL 530 AM EDT...

AT 456 AM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
STRONG THUNDERSTORM OVER SEQUOYAH LAKE... AND MOVING SOUTHEAST AT 25
MPH.

THIS STORM HAS THE POTENTIAL TO PRODUCE FREQUENT CLOUD TO GROUND
LIGHTNING...BRIEF HEAVY RAIN AND WIND GUSTS TO 40 MPH AS IT MOVES
ACROSS NORTHEAST PICKENS...NORTH DAWSON AND SOUTHEAST GILMER
COUNTIES THROUGH 530 AM EDT. SOME LOCATIONS IN THE PATH OF THIS
STORM INCLUDE JASPER...TALKING ROCK...CARTECAY...SEQUOYAH
LAKE...LAKE TAMARACK...MARBLEHILL...FAUSETT LAKE...AMICALOLA FALLS
STATE PARK...LEN FOOTE HIKE INN AND JUNO. HEAVY DOWNPOURS COULD
CAUSE PONDING OF WATER ON ROADWAYS.

&&

LAT...LON 3459 8419 3454 8419 3451 8416 3451 8415
      3438 8421 3450 8453 3467 8444
TIME...MOT...LOC 0858Z 294DEG 22KT 3455 8438