Area Forecast Discussion
Issued by NWS Atlanta, GA

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FXUS62 KFFC 190254 AAD
AFDFFC

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE PEACHTREE CITY GA
1054 PM EDT FRI APR 18 2014

.UPDATE...
ALTHOUGH WINDS HAVE BEEN SLOW TO COME UP...I STILL EXPECT OCCASIONAL
PERIODS OF GUSTY WINDS AT OR OVER ADVISORY CRITERIA THROUGH THE
OVERNIGHT AS THE SURFACE LOW LIFTS OUT OF THE GULF AND MOVES ACROSS
FAR SOUTH GEORGIA. I HAVE EXTENDED THE TIME OF THE ADVISORY ACROSS
CENTRAL GEORGIA TO MATCH THE ADVISORY AREA TO THE NORTH...12Z.
OTHERWISE NO OTHER SIGNIFICANT CHANGES MADE AT THIS TIME.

20

&&

.PREV DISCUSSION... /ISSUED 925 PM EDT FRI APR 18 2014/

UPDATE...
HAVE MADE SOME ADJUSTMENTS TO THE SHORT TERM FORECAST GRIDS...MAINLY
MINOR...TO FIT CURRENT AND EXPECTED TENDS. STILL EXPECTING MODERATE
RAIN TO CONTINUE OVER THE FLOOD WATCH AREA FOR THE REMAINDER OF THE
EVENING INTO THE EARLY MORNING SO NO CHANGES ARE PLANNED FOR THE
FLOOD WATCH AT THIS TIME. WINDS ARE SLOW TO COME UP BUT I DO STILL
EXPECT A GRADUAL INCREASE THROUGH THE EVENING. FORECAST VALUES ARE
BORDERLINE FOR THE WIND ADVISORY...HOWEVER WITH VERY MOIST SOIL AND
TREES THAT ARE WELL INTO THE LEAFING OUT PROCESS...I THINK THAT IT
REMAINS ADVISABLE TO KEEP THE WIND ADVISORIES GOING.

20

PREV DISCUSSION... /ISSUED 745 PM EDT FRI APR 18 2014/

UPDATE...
WE HAVE DECIDED TO EXPAND THE FLOOD WATCH NORTHWARD TO INCLUDE MOST
OF THE ATLANTA METRO AREA INTO NORTHEAST GEORGIA...ROUGHLY NORTHWARD
TO JUST NORTH OF THE I-85 CORRIDOR...BASED ON RADAR/SATELLITE TRENDS
DEPICTING THE PERSISTENT DEFORMATION ZONE PRECIPITATION ASSOCIATED
WITH THE UPPER LOW. WE WILL LIKELY SEE A QUICK 1 TO 2 INCHES OF
ADDITIONAL RAIN THROUGH THE EVENING ACROSS THE WATCH AREA. ALTHOUGH
THIS IS NOT LIKELY TO CAUSE WIDESPREAD FLOODING ISSUES IN THE NEW
WATCH AREA...THERE IS LIKELY TO BE AT LEAST ISOLATED TO SCATTERED
PROBLEMS OVERNIGHT.

20

PREV DISCUSSION... /ISSUED 300 PM EDT FRI APR 18 2014/

SHORT TERM /TONIGHT THROUGH SATURDAY NIGHT/...
OF COURSE THE MAIN STORY THROUGH THE SHORT TERM IS THE RAIN.
CLASSICAL CAD REMAINS IN PLACE RIDGING DOWN THE EASTERN SEABOARD BUT
IS IN THE PROCESS OF ERODING AS A STRONG UPPER WAVE MOVES ACROSS THE
SOUTHEAST...DEEPENING AND STRENGTHENING TO A CLOSED OFF LOW. A
SURFACE REFLECTION IS MOVING OUT OF THE GULF OF MEXICO AND INTO THE
FLORIDA PANHANDLE AT AFD TIME...AND IT SHOULD WORK ITS WAY EAST
NORTHEAST GENERALLY ALONG THE FLORIDA-GEORGIA BORDER. WIDESPREAD
GULF MOISTURE CONTINUES TO STREAM ACROSS THE SOUTHEAST. CONVECTION
IN FLORIDA IS ORIENTED NORTH-SOUTH /INSTEAD OF EAST-WEST/ SO IS NOT
ACTING TO CUT OFF ANY INFLOW...RATHER...IF ANYTHING...THE CONVECTIVE
ACTIVITY AND ASSOCIATED LATENT HEAT RELEASE IS LIKELY CONTRIBUTING
TO OVERALL ATMOSPHERIC MOISTURE CONTENT. A BIT OF DRY-SLOTTING
LEADING TO A REDUCTION IN RAIN ACROSS SOUTHWEST GEORGIA TOWARD
TALLAHASSEE...WITH HEFTY AMOUNTS ACROSS ALABAMA UNDERNEATH THE UPPER
WAVE ASSOCIATED WITH THE DEFORMATION AXIS. WILL PROBABLY SEE SOME OF
THE DRY-SLOTTING MOVE ACROSS THE SOUTHERN TIER OF OUR AREA BUT AS
THE ENTIRE SYSTEM MOVES EAST ALL HIRES AND SYNOPTIC GUIDANCE BRINGS
THIS DEFORMATION ZONE ACROSS CENTRAL GEORGIA. SEE HYDRO SECTION
BELOW FOR MORE ON QPF.

WITH THE WIDESPREAD RAIN...TEMPERATURES TODAY HAVE HELD PRETTY
STEADY IN THE LOWER TO MID 50S WITH WARMEST AREAS IN NORTHWEST
GEORGIA WHERE CLOUD COVER IS A LITTLE THINNER AND NOT QUITE AS MUCH
RAIN REACHING THE GROUND JUST YET DUE TO THE DRY DEWPOINTS.
EVAPORATIVE COOLING CONTRIBUTING TO THIS AS WELL. SHOULD DEFINITELY
SEE RECORD COLD HIGH AT CSG FOR TODAY AND STILL FLIRTING WITH IT AT
MCN. SO WITH THAT...NOT A HUGE DIURNAL RANGE FOR TONIGHT BUT SHOULD
STILL GET INTO THE 40S EVERYWHERE EXCEPT POSSIBLY EXTREME SOUTHEAST
ZONES WHERE THEY STAY NEAR 50 OR LOWER 50S. /WITH THE DEFORMATION
AXIS SETTING UP FOR TONIGHT IMAGINE IF IT WERE 15 DEGREES
COLDER...YIKES./ DEFINITELY WARMER ON SATURDAY STILL 10 OR SO
DEGREES BELOW NORMAL. SHOULD SEE AN AREA OF LINGERING PRECIP ACROSS
THE AREA AT LEAST THROUGH 18Z AS SURFACE FLOW SHIFTS OFF THE
ATLANTIC BRINGING ADDITIONAL LOW-LEVEL MOISTURE TO THE AREA. CLOUD
COVER ASSOCIATED WITH THE UPPER LOW WILL LINGER THROUGH THE REST OF
THE DAY SATURDAY WITH POPS LINGERING OVERNIGHT THROUGH EXTREME
SOUTHEAST ZONES.

STRONG SURFACE INVERSION REMAINS IN PLACE WITH THE DAMMING. JUST OFF
THE SURFACE HOWEVER...925MB WINDS ARE PROGGED UPWARDS OF 60KT ACROSS
SOME OF THE AREA. EVEN WITH THE INVERSION TO KEEP THIS JET JUST OFF
THE SURFACE...THERE WILL CONTINUE TO BE ENOUGH OF A SURFACE GRADIENT
TO WARRANT KEEPING THE WIND ADVISORY IN PLACE. EXPECT WINDS TO
INCREASE THIS EVENING AND OVERNIGHT ESPECIALLY ACROSS CENTRAL
GEORGIA. NORTHERN EXTENT OF ADVISORY IS IFFY BUT BETTER TO HAVE IT
OUT THAN NOT.

OTHER CONCERN IS POSSIBILITY OF THUNDER ACROSS THE AREA. JUST A
LITTLE MUCAPE CREEPING INTO SOUTHERN ZONES AT AFD TIME BUT DO NOT
EXPECT MUCH MORE THAN THAT THIS EVENING AND TONIGHT WITH THE
WIDESPREAD RAIN AND CLOUD COVER. CANNOT RULE OUT ISOLATED THUNDER ON
SATURDAY AS THE LAPSE RATES INCREASE IN RESPONSE TO THE UPPER LOW
MOVING ACROSS...SO HAVE INCLUDED ISOLATED THUNDER WORDING FOR
EXTREME SOUTHEAST ZONES.

TDP

LONG TERM /SUNDAY THROUGH FRIDAY/...
MAINLY ONLY TWEAKS TO THE FORECAST BASED ON THE LATEST GUIDANCE.
FORECAST MLCAPES NOW RUNNING 400-1000 FROM THE GFS AT 18Z TUESDAY
WITH NO SIGNIFICANT SHEAR WITH THE FRONT.
BDL

PREVIOUS DISCUSSION...
MAIN CLOSED LOW JUST OFF THE GA/CAROLINA COAST STAYS FAIRLY
STATIONARY THROUGH SUN AND MON BEFORE WEAKENING AND PUSHING
FURTHER OUT TO SEA TUE. CLOUDS WILL LINGER ACROSS THE AREA SUN
WITH MAYBE A FEW LIGHT SHOWERS SUN MORNING ACROSS SOUTHEASTERN
SECTIONS OF THE CWA. MODELS ARE IN VERY GOOD AGREEMENT THROUGH
MOST OF THE EXTENDED WITH MINOR DIFFERENCES IN TIMING AND AVAILABLE
MOISTURE WITH NEXT SYSTEM TUE.

00Z MON...A SHORTWAVE OVER THE MIDDLE OF THE COUNTRY DEVELOPS INTO
A CLOSED LOW CENTER AND MOVES OVER THE GREAT LAKE STATES BY 00Z
TUE. ITS TRAILING COLDS FRONT SWEEPS THROUGH THE MISSISSIPPI RIVER
VALLEY AND INTO NA GA BY 12Z TUE. WILL SEE SHOWER AND
THUNDERSTORMS SWEEP THROUGH THE STATE TUE AND COULD SEE SOME
FAIRLY STRONG STORMS AS INSTABILITY INDICES ARE INCREASING MODEL
RUN TO MODEL RUN. TEMPS WILL BE A LITTLE ABOVE NORMAL AND WITH
DEWPOINTS IN THE 50S AND LOW 60S...MLCAPE VALUES WILL BE
SUFFICIENT FOR SOME STRONG STORMS. DEEP SHEAR WILL BE SOMEWHAT
WEAK...0-6KM BULK SHEAR ONLY 10 TO 15 KTS. WILL CONTINUE TO
MONITOR. THIS FRONT SHOULD BE EAST OF THE STATE BY 00Z TO 06Z WED
WITH HIGH PRESSURE BUILDING BACK IN FOR WED AND THU.

01

HYDROLOGY...
PORTIONS OF CENTRAL GEORGIA /AMERICUS AND AREAS WEST/ HAVE ALREADY
RECEIVED AND INCH OF RAIN THROUGH 18Z TODAY. MIGHT BE PERIODS OF
BRIEF REDUCTION IN ACTIVITY ACROSS THAT SOUTHERN BORDER WITH THE
DRY-SLOTTING REACHING INTO THE FORECAST AREA...BUT WITH THE
DEFORMATION AXIS MOVING ACROSS THE AREA THAT AREA OF HEAVIER RAIN IN
ALABAMA /WHERE THEY HAVE RECEIVED BETWEEN 1.5-2 INCHES/...EXPECT QPF
TOTALS TO BE PRETTY HEFTY THIS EVENING AND OVERNIGHT. NEW STORM
TOTAL FROM AFD TIME TILL THE END OF THE EVENT BRINGS AN ADDITIONAL 2
INCHES /BASIN-AVERAGE/ TO SOUTHERN ZONES...WITH SOME AREAS SOUTHEAST
OVER 2.5 INCHES. OTHER CONCERN IS THAT RADARS ARE UNDERESTIMATING BY
ABOUT 15 PERCENT TODAY...NOT A WHOLE LOT BUT ENOUGH TO BE AWARE OF.
WITH THIS PROLONGED...WIDESPREAD RAIN WILL DEFINITELY SEE SOME
PROBLEMS ON AREA WATERWAYS ESPECIALLY ACROSS CENTRAL GEORGIA.
LOCATION AND TIMING OF FLOOD WATCH ALREADY IN PLACE LOOKS GOOD. IT
MAY GO A LITTLE LONG BUT WE CAN ALWAYS CANCEL EARLY WHEN RAIN MOVES
OUT.

TDP

CLIMATE...

RECORDS FOR FRIDAY APRIL 18...

               MAX TEMPERATURE         MIN TEMPERATURE
  STATION      HIGH        LOW         HIGH        LOW
  -------  ----------  ----------  ----------  ----------
   KAHN      90 1942     54 1902     64 1969     32 1936
                1927
   KATL      87 2002     50 1983     69 1927     33 1997
                1937
                1896
   KCSG      91 2002     62 1983     69 2006     37 1962
                                                    1956
   KMCN      90 1967     55 1921     66 1922     33 2001
                1955

RECORDS FOR SATURDAY APRIL 19...

               MAX TEMPERATURE         MIN TEMPERATURE
  STATION      HIGH        LOW         HIGH        LOW
  -------  ----------  ----------  ----------  ----------
   KAHN      91 1917     51 1984     64 1927     30 1983
   KATL      88 1941     50 1983     66 1927     30 1983
   KCSG      91 2002     59 1983     68 1995     33 1983
                            1953
   KMCN      91 2002     59 1910     66 1927     31 1983
                1976
                1968

AVIATION...
00Z UPDATE...
SOLID AREA OF IFR TO MVFR CONDITIONS ACROSS CENTRAL GEORGIA WITH A
TIGHT NORTH-SOUTH GRADIENT FROM IFR/MVFR TO VFR ACROSS NORTH
GEORGIA. I DO EXPECT MVFR AND EVENTUALLY IFR CONDITIONS TO EXPAND
NORTHWARD ACROSS ALL TAF SITES WITH ALL SITES IFR BY 06Z. SHOULD SEE
IMPROVEMENT TO MVFR MOST AREAS AFTER 12Z...CONTINUING THROUGH 00Z.
WINDS WILL REMAIN NORTHEASTERLY THROUGH THE PERIOD STARTING 6-14KT
WITH GUSTS 14-24KT...INCREASING TO 10-18KT WITH GUSTS 17-29KT BY
06Z. WIDESPREAD LIGHT TO MODERATE RAIN...WITH EMBEDDED SHOWERS...
WILL CONTINUE AREAWIDE THROUGH 06Z...DIMINISHING FROM WEST TO EAST
THROUGH THE REMAINDER OF THE FORECAST PERIOD.

//ATL CONFIDENCE...00Z UPDATE...
MEDIUM.

20

&&

.PRELIMINARY POINT TEMPS/POPS...
ATHENS          45  60  48  71 / 100  70  20  10
ATLANTA         46  62  49  70 / 100  50  20   5
BLAIRSVILLE     44  62  47  72 /  80  50  10   5
CARTERSVILLE    47  64  50  72 / 100  30  10   5
COLUMBUS        48  63  51  73 / 100  30  10   5
GAINESVILLE     46  60  49  70 / 100  60  20   5
MACON           48  61  51  72 / 100  50  20   5
ROME            48  65  49  73 /  70  20  10   5
PEACHTREE CITY  47  62  49  71 / 100  50  10   5
VIDALIA         52  64  54  70 / 100  50  40  20

&&

.FFC WATCHES/WARNINGS/ADVISORIES...
FLOOD WATCH THROUGH SATURDAY EVENING FOR THE FOLLOWING ZONES:
BALDWIN...BANKS...BARROW...BIBB...BLECKLEY...BUTTS...CARROLL...
CHATTAHOOCHEE...CLARKE...CLAYTON...COBB...COWETA...CRAWFORD...
CRISP...DEKALB...DODGE...DOOLY...DOUGLAS...EMANUEL...FAYETTE...
FORSYTH...GLASCOCK...GREENE...GWINNETT...HALL...HANCOCK...
HARRIS...HEARD...HENRY...HOUSTON...JACKSON...JASPER...
JEFFERSON...JOHNSON...JONES...LAMAR...LAURENS...MACON...
MADISON...MARION...MERIWETHER...MONROE...MONTGOMERY...MORGAN...
MUSCOGEE...NEWTON...NORTH FULTON...OCONEE...OGLETHORPE...PEACH...
PIKE...PULASKI...PUTNAM...ROCKDALE...SCHLEY...SOUTH FULTON...
SPALDING...STEWART...SUMTER...TALBOT...TALIAFERRO...TAYLOR...
TELFAIR...TOOMBS...TREUTLEN...TROUP...TWIGGS...UPSON...WALTON...
WARREN...WASHINGTON...WEBSTER...WHEELER...WILCOX...WILKES...
WILKINSON.

WIND ADVISORY UNTIL 8 AM EDT SATURDAY FOR THE FOLLOWING ZONES:
BALDWIN...BANKS...BARROW...BARTOW...BIBB...BLECKLEY...BUTTS...
CARROLL...CHATTAHOOCHEE...CHEROKEE...CLARKE...CLAYTON...COBB...
COWETA...CRAWFORD...CRISP...DAWSON...DEKALB...DODGE...DOOLY...
DOUGLAS...EMANUEL...FAYETTE...FLOYD...FORSYTH...GLASCOCK...
GREENE...GWINNETT...HALL...HANCOCK...HARALSON...HARRIS...HEARD...
HENRY...HOUSTON...JACKSON...JASPER...JEFFERSON...JOHNSON...
JONES...LAMAR...LAURENS...LUMPKIN...MACON...MADISON...MARION...
MERIWETHER...MONROE...MONTGOMERY...MORGAN...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...TREUTLEN...TROUP...
TWIGGS...UPSON...WALTON...WARREN...WASHINGTON...WEBSTER...
WHEELER...WHITE...WILCOX...WILKES...WILKINSON.

&&

$$

SHORT TERM...20
LONG TERM....39
AVIATION...20





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