Special Weather Statement, NWS Atlanta, GA

AREA FORECAST DISCUSSION...UPDATED FOR AVIATION
NATIONAL WEATHER SERVICE PEACHTREE CITY GA
140 AM EDT FRI MAY 27 2011

.UPDATE...
/ISSUED AT 714 PM EDT THU MAY 26 2011/
CONTINUING TO DO FREQUENT UPDATES TO TRY AND STAY AHEAD
OF THIS SYSTEM WHICH HAS SHOWN MORE STAYING POWER THAN MODELS HAVE
INDICATED. WIDESPREAD LARGE HAIL REPORTS ALONG WITH AN INCREASING
NUMBER OF WIND REPORTS THIS EVENING. FOR THE LATEST
UPDATE...ALLOWED WW 379 TO EXPIRE BUT CONTINUE WITH 384. HAVE BEEN
RELUCTANT TO TRIM ANYTHING OFF OF 384 BUT BASED ON RADAR
TRENDS...SHOULD BE ABLE TO WITHIN THE NEXT HOUR.

&&

.PREV DISCUSSION... /ISSUED 218 PM EDT THU MAY 26 2011/

..SEVERE STORMS LIKELY INTO TONIGHT...
..LARGE HAIL AND DAMAGING WINDS THE MAIN CONCERNS...

SHORT TERM /TONIGHT THROUGH SATURDAY NIGHT/...

REGIONAL SURFACE ANALYSIS SHOWS SURFACE TROUGH HAS PROGRESSED INTO
THE TENNESSEE VALLEY AND EXTENDS SOUTHWARD INTO NORTHERN ALABAMA
AND INTO THE GULF COAST OF MISSISSIPPI AND LOUISIANA. THUNDERSTORM
ACTIVITY ALONG AND AHEAD OF THIS FEATURE WAS BEING AIDED BY A BAND
OF MID LEVEL VORTICITY SHOWN BY LATEST RUC ANALYSIS WHICH IS AHEAD
OF THE MAIN MID LEVEL LOW OVER THE OHIO VALLEY. LOOKING AT THE
THERMODYNAMIC PROFILES...ATMOSPHERE IS BECOMING INCREASINGLY
CONDUCIVE TO SUPPORT ROBUST UPDRAFTS WITH THE MIXED LAYER CAPE NOW
IN EXCESS OF 2000 J/KG ALONG AND NORTH OF THE INTERSTATE 85
CORRIDOR. IN ADDITION...MID LEVEL LAPSE RATES ARE QUITE IMPRESSIVE
WITH VALUES NEARING 8 OVER SOUTHERN SECTIONS OF THE FORECAST AREA.
PUTTING THIS ALL TOGETHER LEADS ONE TO THE CONCLUSION THAT
THUNDERSTORMS WILL BECOME MORE WIDESPREAD THROUGH THIS AFTERNOON
AND EVENING WITH THE BIGGER QUESTION BECOMING THE EXTENT OF SEVERE
EXPECTED.

LOOKING AT THE ANALYZED SHEAR VALUES...50 KT CONTOUR AT 850 MB HAS
MADE ITS WAY INTO NORTH GA BUT THIS REALLY TAILS OFF TO THE SOUTH
WHERE 18Z SOUNDING IS ONLY SHOWING 20 KTS OR SO AT FFC. IN
ADDITION...HELICITY VALUES ARE NOT THAT IMPRESSIVE WITH THESE
STORMS...SO TORNADO POTENTIAL STILL APPEARS MINIMAL. TO SUM
UP...SEVERE WIND THREAT MAINLY ACROSS THE NORTHERN HALF...BUT HAIL
LIKELY WITH ANY SUSTAINED UPDRAFTS GIVEN LAPSE RATES AND INCREASED
PARTICLE SEPARATION DUE TO FLOW ALOFT. OF NOTE RECENTLY HAS BEEN
THE WRF SUITE WHICH HAS BEEN SHOWING THIS ACTIVITY TRANSLATING
EASTWARD QUICKLY DURING THE OVERNIGHT HOURS BUT MAINTAINING A GOOD
PORTION OF ITS INTENSITY DESPITE THE LOSS OF HEATING.

ACTIVITY SHOULD EVENTUALLY WANE LATE TONIGHT AND SHORT TERM MODELS
HAVE BEEN IN GENERAL MORE PROGRESSIVE WITH THE PATTERN...SHUNTING
MOST OF THE DEEP LAYER MOISTURE EAST OF I75 BY FRIDAY AFTERNOON.
WILL STILL STAY ON THE HIGH SIDE OF GUIDANCE GIVEN CONTINUED
INSTABILITY ALOFT ON FRIDAY AND THE FACT THAT WINDS REMAIN SOUTH
TO SOUTHWEST FOR EASTERN PORTIONS OF THE FORECAST AREA THROUGH
LATE FRIDAY AFTERNOON.

WITH MID LEVEL TROUGH SHIFTING EAST OF THE AREA BY SATURDAY AND
DEEPER MOISTURE CONTINUING TO DECREASE...ENOUGH CONFIDENCE EXISTS
TO PULL POPS FOR THE WESTERN HALF OF THE FORECAST AREA AND
ADVERTISE JUST 20 POPS FOR THE EXTREME EAST. THIS TOO MAY PROVE TO
BE TOO MUCH IN THE END WITH SATURDAY POSSIBLY BEING DRY AREAWIDE.

LONG TERM /SUNDAY THROUGH THURSDAY/...MAIN FEATURE THROUGH THE
EXTENDED WILL BE THE DOMINANT UPPER HIGH WHICH BUILDS OVER THE
REGION THROUGH EARLY NEXT WEEK. SOME INDICATIONS THAT HIGH
RETROGRADES ENOUGH ON MONDAY TO ALLOW PULSE CONVECTION TO DEVELOP
OVER THE MOUNTAINS BUT NOT ENOUGH EVIDENCE TO MODIFY EXTENDED
PORTION SIGNIFICANTLY AT THIS TIME.

&&

.AVIATION...
06Z UPDATE...
CLUSTERS OF SHOWERS AND THUNDERSTORMS STILL DEVELOPING AND MOVING
NE. WILL HOLD MENTION OF THUNDER IN TAF SITES FOR ANOTHER COUPLE OF
HOURS AT LEAST. WET GROUNDS AND LIGHT SW WINDS WILL RESULT IN LOW
IFR CIGS DEVELOPING BY AROUND 09Z...THEN GRADUAL IMPROVEMENT TO
VFR BY 16Z. AT 16Z... EXPECT SCT SHOWERS WITH ISOLATED CB'S TO
DEVELOP IN ATLANTA AREA AND EASTWARD. THE GREATER TSTM THREAT SHOULD
BE EAST OF ATL TODAY. WINDS LIGHT SOUTHWEST OR VARIABLE TONIGHT WITH
OCCASIONAL GUSTS IN THUNDERSTORMS. SOUTHWEST WINDS 10KT AFTER 14Z
TODAY.

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

41

&&

.PRELIMINARY POINT TEMPS/POPS...
ATHENS          64  82  62  87 /  70  40  20  20
ATLANTA         65  82  65  86 /  90  30  10   5
BLAIRSVILLE     62  76  56  82 /  90  40  10   5
CARTERSVILLE    61  81  58  89 /  90  30  10   5
COLUMBUS        67  87  67  91 /  90  30  10   5
GAINESVILLE     63  79  62  85 /  90  40  10  10
MACON           66  86  64  92 /  60  40  20  10
ROME            63  84  56  91 /  70  20  10   5
PEACHTREE CITY  62  83  58  89 /  90  30  10   5
VIDALIA         70  86  69  89 /  50  50  30  20

&&

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

DEESE

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE PEACHTREE CITY GA
631 AM EDT THU MAY 26 2011

GAZ001>009-011>016-019>025-027-030>039-041>062-066>076-078>086-
089>098-102>113-271045-
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-
631 AM EDT THU MAY 26 2011

THIS HAZARDOUS WEATHER OUTLOOK IS FOR NORTH AND CENTRAL GEORGIA.

.DAY ONE...TODAY AND TONIGHT
SCATTERED TO NUMEROUS THUNDERSTORMS ARE EXPECTED OVER NORTH AND
CENTRAL GEORGIA THIS AFTERNOON AND TONIGHT. A FEW THUNDERSTORMS
MAY BE SEVERE OVER NORTH GEORGIA THIS AFTERNOON AND EVENING.

.SYNOPSIS...
HIGH PRESSURE CENTERED OVER THE SOUTHEASTERN STATES WILL CONTINUE
TO WEAKEN AS LOW PRESSURE MOVES THROUGH THE OHIO VALLEY TODAY AND
TONIGHT. A TRAILING COLD FRONT WILL APPROACH NORTHWEST GEORGIA TONIGHT.

.PRIMARY HAZARDS...
THE PRIMARY HAZARD WILL BE DAMAGING WINDS. LARGE HAIL AND AN
ISOLATED TORNADO ARE POSSIBLE.

.DISCUSSION...
A STRONG UPPER LOW PRESSURE SYSTEM WILL MOVE NORTHEASTWARD FROM
THE MID MISSISSIPPI VALLEY INTO THE OHIO VALLEY THROUGH TONIGHT. A
MODERATELY UNSTABLE AIR MASS AND STRONG WIND SHEAR WILL SUPPORT
SCATTERED TO NUMEROUS THUNDERSTORMS. THE MOST FAVORED AREA FOR ANY
SEVERE THUNDERSTORMS WILL BE ATLANTA TO ATHENS NORTHWARD THIS
AFTERNOON AND EVENING.

.DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY
THERE IS A CHANCE OF THUNDERSTORMS FRIDAY AND SATURDAY...AND AGAIN
WEDNESDAY.

.SPOTTER INFORMATION STATEMENT...
SPOTTERS SHOULD MONITOR THE LATEST INFORMATION FOR POSSIBLE
ACTIVATION ACROSS NORTH GEORGIA.

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE PEACHTREE CITY GA
137 AM EDT FRI MAY 27 2011

GAZ074-084-270615-
137 AM EDT FRI MAY 27 2011

...SIGNIFICANT WEATHER ADVISORY FOR PENNY-SIZED HAIL AND FREQUENT
LIGHTNING IN WASHINGTON AND EASTERN WILKINSON COUNTIES UNTIL 215 AM
EDT...

AT 131 AM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
STRONG THUNDERSTORM 6 MILES NORTH OF TOOMSBORO...MOVING NORTHEAST AT
20 MPH.

THIS THUNDERSTORM WILL BE CAPABLE OF PRODUCING PENNY-SIZED HAIL AND
POTENTIALLY WIND GUSTS TO 40 MPH.  FREQUENT CLOUD-TO-GROUND
LIGHTNING IS ALSO OCCURRING WITH THIS THUNDERSTORM. RESIDENTS IN
THIS AREA SHOULD STAY INDOORS. ELECTRICAL APPLIANCES AND TELEPHONES
SHOULD NOT BE USED UNLESS IN AN EMERGENCY.

&&

LAT...LON 3279 8310 3295 8320 3299 8312 3298 8312
      3295 8307 3297 8307 3299 8305 3303 8307
      3314 8287 3294 8273
TIME...MOT...LOC 0536Z 240DEG 16KT 3292 8305

19

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE PEACHTREE CITY GA
213 AM EDT FRI MAY 27 2011

GAZ074-085-097-270645-
213 AM EDT FRI MAY 27 2011

...SIGNIFICANT WEATHER ADVISORY FOR PENNY-SIZED HAIL AND FREQUENT
CLOUD-TO-GROUND LIGHTNING IN WASHINGTON...NORTHEASTERN LAURENS AND
JOHNSON COUNTIES UNTIL 245 AM EDT...

AT 209 AM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
CLUSTER OF STRONG THUNDERSTORMS ACROSS THE INDICATED COUNTIES. ONE
STRONG STORM WAS LOCATED NEAR DONOVAN AND ANOTHER WAS LOCATED
BETWEEN LOVETT AND DUBLIN...WITH A THIRD NEAR HARLOW. THE STORMS
WERE MOVING NORTHEAST AT 25 MPH.

PENNY-SIZED HAIL WILL BE POSSIBLE WITH THE STRONGER STORMS IN THIS
AREA...ALONG WITH WIND GUSTS TO 35 MPH AND FREQUENT CLOUD-TO-GROUND
LIGHTNING.

&&

LAT...LON 3243 8298 3255 8309 3301 8255 3295 8254
      3292 8251 3282 8252 3276 8245
TIME...MOT...LOC 0611Z 238DEG 22KT 3276 8272

19

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