Special Weather Statement, NWS Atlanta, GA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PEACHTREE CITY GA
1131 AM EDT SAT JUL 30 2011

.UPDATE...
CONVECTION ENTERING NW GA THIS MORNING ASSOCIATED SHORTWAVE
USHERED IN BY NORTHWEST FLOW. TEMPERATURES AND DEW POINTS LOOKS TO
BE ON TRACK...BUT HAVE ADJUSTED POPS SLIGHTLY ACROSS NORTH GEORGIA
FOR THIS MORNING AND AFTERNOON TO ACCOUNT FOR LATEST ACTIVITY.
PRECIP EXPECTED TO STAY ACROSS NORTH GEORGIA...WITH THE REMAINING
CWA SHELTERED BY RETREATING RIDGE. NO ADDITIONAL UPDATES ARE
EXPECTED AT THIS TIME.

31

&&

.SHORT TERM /TODAY THROUGH MONDAY/...
/ISSUED 434 AM EDT SAT JUL 30 2011/
STRONG 596DM SUBTROPICAL RIDGE...CENTERED OVER N GA FRI...WILL DRIFT
BACK WEST TOWARD OK BY 00Z SUN...THEN MEANDER ABOUT THE OK/AR/TX
REGION THROUGH MUCH OF NEXT WEEK. CONSEQUENTLY...THIS WILL ONCE
AGAIN PLACE GA AND THE SE U.S. IN A MORE ACTIVE NW FLOW ALOFT.
ALTHOUGH DEEP TROPICAL MOISTURE HAS REMAINED OVER THE AREA THE PAST
SEVERAL DAYS...THE PROXIMITY OF THE UPPER RIDGE AND ASSOCIATED
SUBSIDENCE HAS GREATLY SUPPRESSED CONVECTION. COVERAGE THE LAST
COUPLE OF DAYS HAS BEEN ON THE ORDER OF 10 PERCENT...LITTLE OF WHICH
HAS EVEN PRODUCED LIGHTNING. SUBTLE CHANGES RESULTING FROM INCREASED
NW FLOW ALOFT WILL LIKELY YIELD SIGNIFICANT CHANGES IN CONVECTIVE
COVERAGE TODAY...AND ESPECIALLY SUN-MON AS A NW FLOW SHORT WAVE AND
ASSOCIATED WEAK FRONT DRIFT SOUTH INTO THE REGION. TROPICAL MOISTURE
IS DEEPLY ENTRENCHED ACROSS THE REGION. PWS INCREASE FROM 1.7 AT 00Z
SUN TO AN EXTREMELY MOIST 2.3 INCHES BY 00Z MON. 500MB TEMPS
DECREASE SLIGHTLY FROM -4C TO -6C...JUST ENOUGH AT THIS TIME OF YEAR
TO RESULT IN A MARKED INCREASE IN CONVECTION.

FOR TODAY...EXPECT AN INCREASE IN CONVECTION ACROSS MAINLY NW
GA...MOST SUSCEPTIBLE TO THE AFOREMENTIONED SYNOPTIC CHANGES AND
APPROACHING FRONT/NW FLOW SHORT WAVE...WHILE THE REMAINDER OF THE
CWA REMAINS SOMEWHAT IMPACTED BY THE RECEDING RIDGE.
SUN-MON...EXPECT WIDESPREAD...MAINLY DIURNAL DRIVEN CONVECTION. WITH
PWS WELL ABOVE 2.0 INCHES...HEAVY RAIN AND EVEN LOCALIZED FLASH
FLOODING...ESPECIALLY IN HEAVILY URBANIZED AREAS AND MOUNTAINOUS
AREAS...WILL BE THE MAIN CONCERN. THIS WILL NEED TO BE WATCHED VERY
CAREFULLY ON AN INDIVIDUAL BASIS...ESPECIALLY WITH LIGHT STEERING
CURRENTS AND HIGH PWS. AT THIS TIME...AM NOT ISSUING AN FFA AS
COVERAGE OF VERY HEAVY RAIN PRODUCING STORMS SHOULD ONLY BE
SCATTERED. THE SEVERE THREAT APPEARS QUITE LOW. CAPES GENERALLY 1500
OR LESS...NOTHING IMPRESSIVE FOR LATE JULY BY ANY MEANS. SHEAR IS
ESSENTIALLY NON-EXISTENT. HOWEVER...SPC HAS PLACED THE FAR NORTH IN
A 5 PERCENT RISK FOR DAMAGING THUNDERSTORM WINDS TODAY...AND THE
ENTIRE CWA SUN-MON...FOR POSSIBLE HEAVY PRECIPITATION LOADING IN THE
STRONGEST STORMS. AGAIN...OVERALL SEVERE THREAT IS LOW AND HEAVY
RAIN WILL BY FAR BE THE MAIN CONCERN.

PREFER THE MAV MOS POPS OVER THE MET MOS POPS FOR THE SHORT TERM.
THE MET MOS POPS ARE TOO HIGH TODAY AND TOO LOW FOR SUN...OWING TO
THE NAMS RATHER POOR HANDLING OF OVERALL DYNAMICS. THIS IN TURN
LEADS TO THE MET MOS MAX TEMPS BEING TOO LOW TODAY...ESPECIALLY IN
NW GA. PREFER A MAV/MET BLEND...WITH A BIAS TOWARD THE MAV FOR MAX
TEMPS TODAY. FOR MIN TEMPS...A MAV/MET BLEND OR EVEN PERSISTENCE
WILL RULE. IT WILL REMAIN VERY MUGGY AT NIGHT...WITH ATL NOT LIKELY
TO DROP BELOW 75/76 NEXT COUPLE OF DAYS. MAV MAX TEMPS
SUN...ESPECIALLY ACROSS THE NORTH ARE TOO WARM AND UNREASONABLE
GIVEN EXPECTED INCREASE IN CONVECTION AND COOLING 850MB TEMPS...BUT
LOOK BETTER FOR MON. A MAV/MET BLEND WILL BE THE BEST OPTION FOR MAX
TEMPS NEXT FEW DAYS...AS IT HAS BEEN THE PAST SEVERAL CYCLES.

19

.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
/ISSUED 434 AM EDT SAT JUL 30 2011/
SURPRISINGLY ENOUGH FOR LATE JULY...BOTH THE ECMWF AND GFS AGREE
THAT THE SHORT TERM FRONT WILL BE PUSHED INTO SOUTH GA BY TUE...AND
COMPLETELY SOUTH OF THE CWA BY WED. WEAK HIGH PRESSURE BUILDS
SOUTHWARD FROM THE OHIO VALLEY WITH VERY DRY MID-LEVEL AIR AND
SLIGHTLY DRIER SFC AIR PROGGED TO FILTER INTO THE AREA FROM THE
NORTH. THE MAMMOTH SUBTROPICAL RIDGE REMAINS CENTERED IN THE
SOUTHERN PLAINS...BUT BEGINS TO EXPAND EASTWARD. A DEEP TROUGH
EVOLVES OFF THE EAST COAST. THIS PATTERN WOULD INDEED RESULT IN
INCREASED SUBSIDENCE AND DRYING ACROSS OUR CWA. MEX MOS POPS ARE
GENERALLY REDUCED TO LESS THAN 10 PERCENT FOR THE LATER HALF OF THE
WEEK ACROSS MUCH OF THE CWA. I ALWAYS TREAD WITH CAUTION ON ANY SUCH
ADVERTISED DRYING AT THIS TIME OF YEAR IN THIS REGION OF THE
COUNTRY. HOWEVER...SEEING THE LACK OF CONVECTION THE PAST COUPLE OF
DAYS...I CAN CERTAINLY SUPPORT GREATLY REDUCED POPS DURING AT LEAST
THE FIRST PART OF THE EXTENDED...TUE-WED...COMPARED TO THE SUN-MON
PERIOD. AS ALWAYS WITH THE EASTERN PERIPHERY OF THE UPPER
RIDGE...THE DOOR REMAINS OPEN FOR ADDITIONAL DISTURBANCES TO MOVE
SOUTH FROM THE MIDWEST AND OHIO VALLEY. SUCH WILL BE THE CASE BY FRI
AS THE NEXT WEAK FRONT AND DISTURBANCE MOVES SOUTH INTO THE AREA.
THE GFS/ECMWF ALSO HINT AT AN INVERTED TROUGH/EASTERLY WAVE
AFFECTING THE REGION TOWARD THE WEEKEND. MODEL DISPARITIES IN TIMING
AND EXTENT OF COVERAGE NORTH OF FL DO NOT SUPPORT MORE THAN SLIGHT
CHC/LOW CHC POPS IN THE LATER PORTIONS OF THE EXTENDED AT THIS TIME.
THE GFS EVEN DEPICTS A HURRICANE OFF THE SE U.S. COAST BY NEXT
WEEKEND...WHILE THE ECMWF SHOWS NO SUCH SYSTEM. NW FLOW ALOFT SHOULD
KEEP ANY SUCH SYSTEM EAST OF THE U.S.

IT WILL REMAIN HOT AND HUMID THROUGH THE EXTENDED PERIODS...BUT
COMPARED TO WHAT TX/OK WILL/HAVE ENDURED FOR WEEKS ON END...IT IS
REALLY NOT THAT BAD HERE. 850MB TEMPS ARE PROGGED TO RISE BACK INTO
THE +22C TO +24C RANGE BY MID-WEEK...WHICH WOULD SUPPORT THE USUAL
SPOTS...MCN...CSG...AHN APPROACHING 100. WITH DEWPOINTS IN THE
70S...THIS WOULD PUSH HEAT INDICES INTO ADVISORY CRITERIA. WILL NEED
TO WATCH...BUT PREVIOUS EVENTS THIS SUMMER HAVE BEEN MARGINAL IN
MEETING CRITERIA OVER A WIDESPREAD AREA. MEX TEMPS LOOK WAY TOO HIGH
IN THE TUE-WED PERIOD BASED ON PAST SIMILAR EVENTS THIS SUMMER...SO
HAVE LOWERED ACROSS THE BOARD.

19

&&

.AVIATION...
/ISSUED 703 AM EDT SAT JUL 30 2011/
12Z UPDATE...
VFR CONDITIONS ANTICIPATED AT ALL TAF SITES THROUGH FORECAST
PERIOD.  NORTHWEST WINDS WILL INCREASE TO 09-13KT RANGE BY
AFTERNOON...DIMINISHING TO 5KTS OR LESS AFTER 02Z...SHIFTING MORE
NORTH BY 15Z. CONVECTION STILL EXPECTED THIS AFTERNOON...ALTHOUGH
LOW CONFIDENCE IN EXACT LOCATION OF DEVELOPMENT WILL CONTINUE CB
IN CIG GROUPS 20-02Z.

//ATL CONFIDENCE...12Z UPDATE...
HIGH ON WINDS...CIGS...VISIBILITY.
MEDIUM TO HIGH ON CONVECTION...LOW ON IMPACT AT ATL.

12

&&

.PRELIMINARY POINT TEMPS/POPS...
ATHENS          97  73  93  74 /  40  30  60  50
ATLANTA         93  76  92  76 /  40  30  60  50
BLAIRSVILLE     85  70  88  69 /  50  40  60  40
CARTERSVILLE    92  71  92  71 /  40  30  60  50
COLUMBUS        95  76  95  76 /  20  20  50  50
GAINESVILLE     93  75  91  74 /  40  30  60  50
MACON           96  74  95  76 /  20  20  50  50
ROME            92  72  91  72 /  50  40  60  50
PEACHTREE CITY  93  72  92  71 /  30  20  60  50
VIDALIA         95  77  94  77 /  20  20  40  50

&&

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

31/12/19

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE PEACHTREE CITY GA
602 AM EDT SAT JUL 30 2011

GAZ001>009-011>016-019>025-027-030>039-041>062-066>076-078>086-
089>098-102>113-311015-
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-
602 AM EDT SAT JUL 30 2011

THIS HAZARDOUS WEATHER OUTLOOK IS FOR NORTH AND CENTRAL GEORGIA.

.DAY ONE...TODAY AND TONIGHT
ISOLATED TO SCATTERED THUNDERSTORMS POSSIBLE THIS AFTERNOON AND EVENING.

.SYNOPSIS...
DEEP TROPICAL MOISTURE REMAINS ACROSS THE SOUTHEAST...AS THE UPPER
LEVEL RIDGE ACROSS THE AREA SHIFTS WEST. THIS WILL AID IN
THUNDERSTORM DEVELOPMENT ACROSS THE AREA.

.PRIMARY HAZARDS...
THE PRIMARY HAZARDS FROM THUNDERSTORMS WILL BE OCCASIONAL CLOUD TO
GROUND LIGHTNING...LOCALLY HEAVY RAIN AND WIND GUSTS TO 35 MPH. THE
MORE FAVORABLE TIME FOR THUNDERSTORM DEVELOPMENT WILL OCCUR BETWEEN
3 PM AND 10 PM.

.DISCUSSION...
DEEP MOISTURE WILL COMBINE WITH AFTERNOON HEATING TO PRODUCE
ISOLATED SHOWERS AND THUNDERSTORMS ACROSS NORTH AND CENTRAL
GEORGIA THROUGH THIS EVENING. CAPE VALUES WILL INCREASE TO 1000 TO
1500 THIS AFTERNOON...MAINLY ACROSS PORTIONS OF NORTH GEORGIA.

.DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY
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
1251 PM EDT SAT JUL 30 2011

GAZ003-004-301715-
1251 PM EDT SAT JUL 30 2011

...SIGNIFICANT WEATHER ADVISORY FOR HEAVY RAIN AND FREQUENT
LIGHTNING IN WHITFIELD AND CATOOSA COUNTIES UNTIL 115 PM EDT...

AT 1248 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
STRONG THUNDERSTORM OVER RINGGOLD...MOVING EAST AT 10 MPH.

THIS THUNDERSTORM WILL PRODUCE FREQUENT CLOUD-TO-GROUND
LIGHTNING...VERY HEAVY RAIN...AND WIND GUSTS TO 35 MPH AS THEY MOVE
EAST ACROSS WHITFIELD AND CATOOSA COUNTY. MINOR FLOODING OF
LOW-LYING AND FLOOD PRONE AREAS WILL BE POSSIBLE DURING THE NEXT
HOUR. RAINFALL AMOUNTS BETWEEN 0.75 AND 1.25 INCHES CAN BE EXPECTED
ACROSS WHITFIELD AND CATOOSA COUNTIES...INCLUDING AREAS AROUND
BEAUMONT...RINGGOLD... BOYNTON... INDIAN SPRINGS...
GRAYSVILLE...SALEM...TUNNEL HILL... DAWNVILLE... VARNELL AND
COHUTTA. DRIVERS SHOULD USE CAUTION AS INTENSE RAINFALL WILL REDUCE
VISIBILITIES. PONDING OF WATER ON ROADWAYS IS ALSO LIKELY.

&&

LAT...LON 3482 8486 3481 8486 3483 8520 3499 8520
      3499 8486
TIME...MOT...LOC 1648Z 270DEG 10KT 3492 8509

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE PEACHTREE CITY GA
129 PM EDT SAT JUL 30 2011

GAZ004-005-007-012-013-301800-
129 PM EDT SAT JUL 30 2011

...SIGNIFICANT WEATHER ADVISORY FOR HEAVY RAIN IN WHITFIELD...
PICKENS...MURRAY...GILMER AND GORDON COUNTIES UNTIL 200 PM EDT...

AT 124 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED
STRONG THUNDERSTORMS FROM BEAVERDALE TO CALHOUN...MOVING EAST AT 20
MPH.

THESE THUNDERSTORM WILL PRODUCE FREQUENT CLOUD-TO-GROUND
LIGHTNING...VERY HEAVY RAIN...AND WIND GUSTS TO 35 MPH AS THEY MOVE
EAST ACROSS WHITFIELD...PICKENS...MURRAY...GILMER...AND GORDON
COUNTIES. MINOR FLOODING OF LOW-LYING AND FLOOD PRONE AREAS WILL BE
POSSIBLE DURING THE NEXT HOUR. RAINFALL AMOUNTS BETWEEN 0.75 AND
1.25 INCHES CAN BE EXPECTED ACROSS THE AREA...INCLUDING
BEAUMONT...RINGGOLD... BOYNTON... INDIAN SPRINGS...
GRAYSVILLE...SALEM...TUNNEL HILL... DAWNVILLE... VARNELL AND
COHUTTA. DRIVERS SHOULD USE CAUTION AS INTENSE RAINFALL WILL REDUCE
VISIBILITIES. PONDING OF WATER ON ROADWAYS IS ALSO LIKELY.

&&

LAT...LON 3486 8462 3485 8450 3468 8444 3441 8460
      3441 8467 3446 8503 3474 8486 3498 8499
      3499 8498 3499 8463
TIME...MOT...LOC 1728Z 279DEG 18KT 3491 8485 3472 8475
          3452 8487