River Flood Warning 226, NWS Atlanta, GA

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE PEACHTREE CITY GA
1259 AM EST MON DEC 23 2013

.PREV DISCUSSION...
SHORT TERM /TONIGHT THROUGH MONDAY NIGHT/...
/ISSUED 247 PM EST SUN DEC 22 2013/
MAIN FORECAST CONCERN IS CONTINUED FLOOD POTENTIAL ACROSS
PORTIONS OF THE AREA WITH SWATH OF ONGOING MODERATE TO HEAVY RAIN.

ENHANCED BAND OF MOISTURE BEING TRANSPORTED BY PERSISTENT SW FLOW
OFF THE GULF WILL ALLOW FOR EXTREMELY EFFICIENT PRECIP...PWATS OF
NEAR 1.7-1.8 AT 3 STANDARD DEVIATIONS ABOVE CLIMO. LATEST HPC QPF
STILL SUGGESTS A BAND OF 2-2.5 INCHES STORM TOTAL FROM TONIGHT
THROUGH MONDAY MORNING WITH ISOLATED HIGHER POSSIBLE. SEE HYDROLOGY
SECTION BELOW FOR MORE DETAILS.

WHILE MAJORITY OF CWA IS CAPE DEPRIVED...MODELS HAVE CONSISTENTLY
BEEN LINGERING SOME 600-700 J/KG SBCAPE MAINLY SOUTH AND EAST OF A
COLUMBUS...TO MACON...TO WASHINGTON LINE. WITH ABOUT 50 KTS 0-6KM
BULK SHEAR...30 KTS OF 0-1KM SHEAR...AND 200-300 M2/S2 OF SRH
JUXTAPOSED WITH THE EASTERN EDGE OF THE STALLED PRECIP
SHIELD...CANNOT RULE OUT ISOLATED STRONG TO SEVERE STORMS INTO THIS
EVENING. DAMAGING WINDS AND AN ISOLATED BRIEF TORNADO WOULD BE THE
MAIN THREATS. THE INSTABILITY...WHICH HAS BEEN THE LIMITING FACTOR
THUS FAR...MAY BE ENHANCED WITH SOME SCATTERING OUT OF CLOUD
COVERAGE LATE IN THE DAY.

UPPER TROUGH SHOULD FINALLY PUSH THE BAND OF MOISTURE EASTWARD ON
MONDAY AS 1040-MB PARENT SFC HIGH SLIDING INTO THE CENTRAL CONUS
HELPS ADVECT THE COLD FRONT SEWD TO START CLEARING THINGS OUT FOR
THE AREA. BY MONDAY NIGHT...MAJORITY OF AREA WILL BE RAIN-FREE AND
MOSTLY CLEAR.

FORECAST TEMPS WILL MAKE MACON CLOSE TO REACHING A RECORD HIGH
MINIMUM TONIGHT...OTHERWISE EXPECT NEAR NORMAL TEMPS MONDAY AND
SLIGHTLY BELOW NORMAL MONDAY NIGHT IN THE POST FRONTAL REGIME.

BAKER

LONG TERM /TUESDAY THROUGH SUNDAY/...
/ISSUED 247 PM EST SUN DEC 22 2013/
NO MAJOR CHANGES WERE MADE TO THE EXTENDED PERIODS AS MODELS
CONTINUE TO AGREE ON HIGH PRESSURE AND DRY CONDITIONS DOMINATING
THROUGH THE WEEKEND. EXPECTING A SLIGHTLY COOLER THAN NORMAL
CHRISTMAS... WITH MORNING LOWS STARTING OUT IN THE 20S. HIGHS WILL
RANGE FROM LOWER 40S NORTH TO LOWER 50S SOUTH. ENJOY.

39

PREVIOUS LONG TERM DISCUSSION /MONDAY NIGHT THROUGH SATURDAY/...
/ISSUED AT 344 AM EST SUN DEC 22 2013/
MODELS IN PRETTY GOOD AGREEMENT THROUGH THE LONG TERM. THE
CURRENT SYSTEM MOVING THROUGH THE CWA WILL EXIT MONDAY NIGHT AND
BY 06Z TUE THE PRECIP WILL BE OUT OF THE CWA. A LONG WAVE TROUGH
TRIES TO SET UP OVER THE EASTERN U.S. WITH A SERIES OF WEAK SHORT
WAVES MOVING THROUGH THE OHIO VALLEY. AT THE MOST THERE COULD BE A
FEW MORE CLOUDS ACROSS THE NORTHERN PART OF THE CWA...OTHERWISE IT
WILL REMAIN DRY ACROSS NORTH AND CENTRAL GEORGIA INTO NEXT
WEEKEND. THE WEAK SHORT WAVES WILL REINFORCE THE COLDER AIR
THROUGH CHRISTMAS...THEN THERE WILL BE A SLOW MODERATION OF
TEMPERATURES INTO NEXT WEEK AS THE UPPER FLOW TRANSITIONS INTO A
MORE ZONAL PATTERN.

17

HYDROLOGY...
/ISSUED 247 PM EST SUN DEC 22 2013/
STALLED FRONT AND SWATH OF ENHANCED DEEP LAYER MOISTURE OFF THE
NORTHERN GULF WILL ALLOW FOR AN ADDITIONAL 2-3 INCHES OF RAINFALL
TONIGHT THROUGH MONDAY MORNING WITH ISOLATED HIGHER AMOUNTS
POSSIBLE. 1-3 INCHES HAVE ALREADY FALLEN ACROSS PORTIONS OF NORTH
AND CENTRAL GEORGIA...EXCEPT FOR THE SOUTHEASTERN TIER. THE FLOOD
WATCH WILL CONTINUE FOR NORTH AND PORTIONS OF CENTRAL GEORGIA.
EXPECTED MODERATE TO HEAVY RAIN OVER THIS AREA WILL CAUSE
SIGNIFICANT POTENTIAL FOR RIVER FLOODING INCLUDING SMALLER CREEKS
AND STREAMS. FLOOD WARNINGS HAVE ALREADY BEEN ISSUED FOR MINOR
FLOODING ALONG SOME CREEKS IN NORTH GEORGIA.

BAKER

&&

.AVIATION...
06Z UPDATE...
CIGS AND VSBYS WILL CONTINUE TO BE VERY VARIABLE THROUGH THE
MORNING AND TAFS LEAN TOWARDS THE LOWER SIDE. AT ATL...THERE IS
STILL THE POTENTIAL FOR THE CIGS AND VSBYS TO DROP LOWER THAN
FORECAST IN THE TAF. AT THIS POINT THOUGH CONFIDENCE WAS TOO LOW
TO INCLUDE. RAIN WILL CONTINUE THROUGH MUCH OF THE MORNING AND
DIMINISH BY LATE MORNING INTO THE AFTERNOON.

//ATL CONFIDENCE...06Z UPDATE...
LOW CONFIDENCE ON VSBYS AND CIGS. MEDIUM CONFIDENCE ON TIMING OF
PRECIP. HIGH CONFIDENCE ON WIND.

11

&&

.PRELIMINARY POINT TEMPS/POPS...
ATHENS          59  33  46  25 /  80  10  10   0
ATLANTA         54  31  43  25 /  80  10   5   0
BLAIRSVILLE     52  27  37  19 /  70  10   5   0
CARTERSVILLE    54  28  43  22 /  70  10   5   0
COLUMBUS        59  34  50  28 /  80  10   5   0
GAINESVILLE     57  32  44  25 /  80  10   5   0
MACON           62  33  52  25 / 100  10   5   5
ROME            53  26  43  21 /  50  10   5   5
PEACHTREE CITY  56  29  45  21 /  80  10   5   0
VIDALIA         67  42  55  31 /  90  30   5   5

&&

.FFC WATCHES/WARNINGS/ADVISORIES...
FLOOD WATCH UNTIL 7 AM EST THIS MORNING FOR THE FOLLOWING ZONES:
BANKS...BARROW...BARTOW...BUTTS...CARROLL...CATOOSA...
CHATTAHOOCHEE...CHATTOOGA...CHEROKEE...CLARKE...CLAYTON...COBB...
COWETA...CRAWFORD...DADE...DAWSON...DEKALB...DOUGLAS...FANNIN...
FAYETTE...FLOYD...FORSYTH...GILMER...GORDON...GREENE...
GWINNETT...HALL...HARALSON...HARRIS...HEARD...HENRY...JACKSON...
JASPER...LAMAR...LUMPKIN...MADISON...MARION...MERIWETHER...
MONROE...MORGAN...MURRAY...MUSCOGEE...NEWTON...NORTH FULTON...
OCONEE...OGLETHORPE...PAULDING...PICKENS...PIKE...POLK...
PUTNAM...ROCKDALE...SOUTH FULTON...SPALDING...STEWART...TALBOT...
TAYLOR...TOWNS...TROUP...UNION...UPSON...WALKER...WALTON...
WHITE...WHITFIELD.

&&

SHORT TERM...11
LONG TERM....37
AVIATION...11

HAZARDOUS WEATHER OUTLOOK...UPDATED
NATIONAL WEATHER SERVICE PEACHTREE CITY GA
1256 PM EST SUN DEC 22 2013

GAZ001>009-011>016-019>025-027-030>039-041>062-066>076-078>086-
089>098-102>113-231030-
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-
1256 PM EST SUN DEC 22 2013

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF NORTH AND CENTRAL
GEORGIA.

.DAY ONE...THIS AFTERNOON AND TONIGHT...

HEAVY RAIN AND ISOLATED STRONG TO SEVERE THUNDERSTORMS REMAIN
POSSIBLE.

WEATHER HAZARDS EXPECTED...
MODERATE TO HEAVY RAIN WILL CAUSE MINOR FLOODING ALONG SOME CREEKS
AND RIVERS THROUGH TONIGHT.
ISOLATED STRONG TO SEVERE STORMS REMAIN POSSIBLE ACROSS PARTS OF
CENTRAL GEORGIA THROUGH THIS EVENING.

DISCUSSION...
A STRONG STORM SYSTEM MOVING ACROSS THE SOUTHEAST WILL BECOME NEARLY
STATIONARY OVER NORTH AND CENTRAL GEORGIA TODAY AND TONIGHT. STRONG
LOW LEVEL WIND SHEAR AND INCREASING INSTABILITY DURING DAYTIME
HEATING COULD PRODUCE A FEW STRONG TO SEVERE STORMS DURING THE
AFTERNOON AND EVENING HOURS. THE THREAT OF STRONG STORMS GREATLY
DIMINISH BY MID TO LATE EVENING AS THE ATMOSPHERE STABILIZES.

IN ADDITION...DUE TO THE SLOW MOVEMENT OF THE SYSTEM...MODERATE
TO HEAVY RAIN IS EXPECTED ACROSS A LARGE PART OF NORTH AND CENTRAL
GEORGIA THIS AFTERNOON AND TONIGHT. RAINFALL AMOUNTS OF 1 TO 3
INCHES HAVE ALREADY FALLEN ACROSS MUCH OF NORTH AND PARTS OF CENTRAL
GEORGIA THROUGH SUNDAY MORNING... AND ANOTHER 1 TO 2 INCHES WITH
ISOLATED HIGHER AMOUNTS ARE STILL POSSIBLE. A FLOOD WATCH IS IN
EFFECT FOR NORTH AND PARTS OF CENTRAL GEORGIA FOR INCREASED
POTENTIAL OF FLOODING ON RIVERS...CREEKS AND STREAMS THROUGH
TONIGHT.

.DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY...
THE THREAT OF FLOODING OF RIVERS...CREEKS AND STREAMS WILL
CONTINUE INTO MONDAY AS THE STORM SYSTEM EXITS THE REGION. WHILE
ADDITIONAL RAINFALL AMOUNTS ON MONDAY WILL BE LIGHT...RUNOFF FROM
THE PREVIOUS DAY OF HEAVY RAIN COULD CONTINUE THE THREAT OF RIVER
FLOODING.

HIGH PRESSURE WILL SETTLE OVER NORTH AND CENTRAL GEORGIA FOR THE
REMAINDER OF THE PERIOD AND THIS WILL BRING DRY AND STABLE
CONDITIONS THROUGH SATURDAY.

.SPOTTER INFORMATION STATEMENT...
ALTHOUGH SPOTTER ACTIVATION WILL NOT BE NECESSARY TODAY... SPOTTERS
ARE ENCOURAGED TO SUBMIT DAMAGE OR FLOODING REPORTS THROUGH THE WEB
BY GOING TO WEATHER.GOV/ATLANTA.