Area Forecast Discussion
Issued by NWS Atlanta, GA

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FXUS62 KFFC 170908
AFDFFC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PEACHTREE CITY GA
508 AM EDT THU APR 17 2014

.SHORT TERM /TODAY THROUGH FRIDAY/...
OVERNIGHT LOW TEMPERATURES HAVE NOT DROPPED AS SIGNIFICANTLY AS
EXPECTED DUE TO SCT-BKN HIGH CLOUDS THAT PREVENTED RADIATIONAL
COOLING. HAVE OPTED TO CONTINUE THE FREEZE WARNING FOR FAR NORTHEAST
GEORGIA WHERE TEMPERATURES WILL STILL DROP TO NEAR OR SLIGHTLY ABOVE
FREEZING. PATCHY AREAS...PARTICULARLY IN THE MOUNTAIN
VALLEYS...COULD STILL SEE SUBFREEZING TEMPERATURES.

DRY CONDITIONS EXPECTED TODAY BEFORE A LOW PRESSURE SYSTEM MOVES
INTO THE AREA FRIDAY. SURFACE HIGH PRESSURE EXTENDING DOWN THE
APPALACHIANS WAS NOSING INTO NORTHEAST GEORGIA THIS
MORNING...RESULTING IN A WEDGE EXPECTED TO BE IN PLACE THROUGH THE
SHORT TERM. LOW PRESSURE OVER THE NORTHERN GULF MOVES NORTHEASTWARD
THROUGH FRIDAY...TRACKING ACROSS THE FLORIDA PANHANDLE AND INTO
SOUTH GEORGIA. HAVE QUICKLY INCREASING POPS AFTER MIDNIGHT
TONIGHT...SPREADING CHANCE TO CATEGORICAL RAIN NORTHWARD AS THE LOW
APPROACHES...KEEPING BEST CHANCES IN THE FAR SOUTHERN TIERS OF COUNTIES.
MODEL SOLUTIONS HAVE HAD SOME DIFFICULTY AGREEING WITH THE NORTHERN
EXTENT AND MAGNITUDE OF THE PRECIPITATION AS THE LOW TRACKS ACROSS
THE AREA...AND HAVE LARGELY GONE WITH A GFS/ECMWF BLEND. MODELS ARE
CONSISTENT WITH KEEPING THE AREA WITHIN THE STABLE AIRMASS ON THE
NORTHERN SIDE OF THE LOW...SO HAVE NO MENTION OF THUNDER. RAINFALL
AMOUNTS OF 1 TO 2 INCHES ARE POSSIBLE ACROSS CENTRAL
GEORGIA...GENERALLY SOUTH OF A LINE FROM COLUMBUS TO MACON TO
LOUISVILLE. AT THIS TIME...WIDESPREAD FLOODING IS NOT A
CONCERN...AND WILL HOLD OFF ON ISSUING A FLOOD WATCH. A WATCH MAY BE
NECESSARY IF LATER MODEL RUNS ADVERTISE A MORE NORTH POSITION OF THE
HIGHEST RAINFALL TOTALS.

DIFFICULT TEMPERATURE FORECAST THROUGH THE SHORT TERM WITH THE
COMBINATION OF THE WEDGE...EXTENSIVE CLOUD COVER...AND
PRECIP...ESPECIALLY FRIDAY. RAW MODEL TEMPERATURES SEEM A LITTLE TOO
FAR FETCHED...KEEPING HIGHS FRIDAY IN THE 40S AND LOW 50S. ON THE
OTHER HAND...MOS GUIDANCE SEEMS TOO WARM FOR THE
SITUATION/ENVIRONMENT. HAVE TRIED TO FIND THE MIDDLE GROUND BETWEEN
THE TWO...TRENDING A LITTLE MORE TOWARD THE RAW MODELS TO FINALLY LAND
ON TEMPERATURES IN THE MID 50S ACROSS MUCH OF THE AREA. SOME
PORTIONS OF NORTHWEST GEORGIA...ALONG THE PERIPHERY OR OUTSIDE OF
THE WEDGE AND EXPECTING THE LEAST AMOUNT OF RAINFALL...COULD SEE
TEMPERATURES IN THE LOW TO MID 60S. IF THESE TEMPERATURES PAN
OUT...WOULD SEE A RECORD MINIMUM HIGH AT CSG...AND WOULD COME WITHIN
TWO DEGREES FOR AHN AND MCN. HAVE ADDED RECORD INFORMATION IN THE
CLIMATE SECTION BELOW FOR REFERENCE.

31


.LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...

LONG TERM PORTION BEGINS WITH LOW PRESSURE TRANSITIONING FROM THE
GULF COAST TO THE ATLANTIC COAST WITH THE GFS SOME 6 HRS FASTER
WITH THIS TRANSITION THAN THE ECMWF. OVERALL...AGREEMENT IS BETTER
AMONG THE MODELS INITIALLY THAN LAST NIGHTS RUNS AND NOW ALL
INDICATE CATEGORICAL POPS FOR AT LEAST SOUTHERN AND EASTERN
SECTIONS OF THE FORECAST AREA. LONG TERM MODELS ALL HAVE A CLOSED
UPPER LOW NOW BUT DIFFERENCES NOW EXIST AS TO HOW PROGRESSIVE THIS
FEATURE MIGHT BE. TRENDS IN MODELS ARE THAT PROGRESS WILL BE SLOW
THOUGH WITH NORTHERLY FLOW ON THE BACK SIDE OF LOW PROVIDING
DRIZZLE AND CLOUDS AT A MINIMUM AND CONTINUED WIDESPREAD SHOWERS
THROUGHOUT SATURDAY AT WORST. FOR NOW...WILL INDICATE MARGINAL IMPROVEMENT
SATURDAY AFTERNOON FROM NW TO SE AND LET DAY SHIFT SEE ANOTHER
MODEL RUN BEFORE DECLARING SATURDAY A TOTAL WASHOUT.

ONCE UPPER LOW MOVES OUT...MODELS IN AGREEMENT THAT FLOW WILL
TRANSITION TO ZONAL ALOFT MAKING TIMING OF EMBEDDED IMPULSES
CHALLENGING. LOOKS LIKE SOME GENERAL AGREEMENT IN MOST IMPRESSIVE
SHORTWAVE MOVING THROUGH TUESDAY. HAVE BEST POPS OVER NW ZONES AND
THEN TRANSITIONING LOWER OVER SE PORTION AS AVAILABLE MOISTURE IS
LOWER. INSTABILITY STILL INDICATED DURING THIS TIMEFRAME WITH CAPE VALUES
IN EXCESS OF 1000 J/KG. SHEAR VALUES NOT AS CONDUCIVE TO SEVERE
WEATHER AS PREVIOUS RUNS BUT SUFFICIENT ENOUGH THAT CONDITIONS
WILL NEED TO BE MONITORED CLOSELY.

DEESE


&&

.CLIMATE...

RECORDS FOR 04-18...FRIDAY

               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

&&

.AVIATION...
06Z UPDATE...
VFR CONDITIONS EXPECTED THROUGH MUCH OF THE PERIOD. MVFR CIGS
POSSIBLE ACROSS PORTIONS OF CENTRAL GEORGIA 09-16Z. EXPECT 3-6KFT
CIGS TO SPREAD ACROSS THE AREA THIS AFTERNOON...GENERALLY 18-20Z.
EAST WINDS WILL INCREASE TO 9-13KT AFTER 12Z WITH GUSTS 15-25KT
BEGINNING MID MORNING.

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

31

&&

.PRELIMINARY POINT TEMPS/POPS...
ATHENS          66  46  57  45 /   5  10  60  20
ATLANTA         62  48  57  46 /   5  10  60  20
BLAIRSVILLE     62  40  55  44 /   5   5  20  10
CARTERSVILLE    65  46  60  46 /   5  10  40  10
COLUMBUS        67  51  57  48 /   5  40 100  30
GAINESVILLE     62  46  54  46 /   5   5  40  20
MACON           66  50  56  47 /   5  30  80  60
ROME            66  45  63  45 /   5   5  30  10
PEACHTREE CITY  66  47  58  44 /   5  20  60  20
VIDALIA         69  53  61  53 /   5  30  90  80

&&

.FFC WATCHES/WARNINGS/ADVISORIES...
FREEZE WARNING UNTIL 9 AM EDT THIS MORNING FOR THE FOLLOWING
ZONES: FANNIN...LUMPKIN...TOWNS...UNION...WHITE.

&&

$$

SHORT TERM...31
LONG TERM....DEESE
AVIATION...31





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