Area Forecast Discussion
Issued by NWS Atlanta, GA

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FXUS62 KFFC 270608
AFDFFC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PEACHTREE CITY GA
208 AM EDT FRI MAR 27 2015

.PREV DISCUSSION... /ISSUED 830 PM EDT THU MAR 26 2015/

EVENING UPDATE...
LATEST SURFACE ANALYSIS SHOWS THE COLD FRONT NOW PUSHING INTO FAR NW
GA... AND TIMING TOOL INDICATES THE FRONT WILL PUSH ACROSS THE
ATLANTA METRO AREA BETWEEN MIDNIGHT AND 2 AM FRIDAY MORNING. EXPECT
THE RAIN SHOWERS TO THE WEST AND SW IN ALABAMA TO PUSH INTO WEST
CENTRAL GA IN THE NEXT HOUR...THEN INTO THE ATLANTA METRO AREA BY 10
PM THIS EVENING IF NOT EARLIER. STILL CANNOT RULE OUT AN ISOLATED
THUNDERSTORM JUST AHEAD OR ALONG THE FRONT...WITH THE GREATER
CHANCES OF THIS OVER CENTRAL GA OVERNIGHT. HAVE UPDATED ZONES TO
TWEAK LOWS DOWN A DEGREE OR SO BASED ON TEMPS SEEN UPSTREAM BEHIND
THE FRONT... AND TO ADJUST POPS AND TIMING OF MENTION OF THUNDER.
OTHERWISE... REST OF FORECAST LOOKS ON TRACK WITH SHOWERS LIKELY ALL
ZONES AND GUSTY NW WINDS MOVING IN BEHIND THE FRONT OVERNIGHT. /39

SHORT TERM /TONIGHT THROUGH FRIDAY NIGHT/...
/ISSUED AT 339 PM EDT THU MAR 26 2015/
CONVECTION IN THE GULF HAS HELPED TO SUPPRESS ACTIVITY ACROSS THE
CWA AND ONLY A FEW LIGHT SHOWERS HAVE BEEN NOTED ACROSS THE AREA
TODAY. RAIN TO THE SOUTH IS SLOWLY MOVING NORTHWARD...HOWEVER IT
APPEARS THE BULK OF THE PRECIPITATION AT THIS POINT WILL BE
OVERNIGHT AND MORE ASSOCIATED WITH THE COLD FRONT. INSTABILITY IS
DECENT ENOUGH WITH MU CAPE AROUND 500 J/KG IN THE GFS AND 1000 J/KG
IN THE NAM THAT I HAVE CONTINUED THE SLIGHT CHANCE OF THUNDERSTORMS
OVERNIGHT /WITH HIGHER RAIN CHANCES/. NOT EXPECTING SEVERE STORMS
OVERNIGHT...HOWEVER STILL COULD SEE SOME GUSTY WINDS OR SMALL HAIL
WITH THE ISOLATED THUNDERSTORMS.

COLD FRONT WILL MOVE INTO SOUTH GEORGIA TOMORROW AND MAY SEE SOME
SHOWERS ACROSS THE SOUTHEAST PART OF THE CWA IN THE MORNING...BUT
THUNDERSTORMS SHOULD HAVE DIMINISHED BY THEN. WILL SEE WINDS
INCREASE LATE TONIGHT/TOMORROW BEHIND THE FRONT WITH SUSTAINED
VALUES AROUND 15MPH /BUT BELOW WIND ADVISORY CRITERIA OF 20MPH/.

WILL NEED TO WATCH TRENDS FOR FRIDAY AFTERNOON INTO THE EVENING
CLOSELY. MODELS ARE HINTING AT LIGHT PRECIP ACROSS THE FAR
NORTH...BUT FOR NOW HAVE ONLY MENTIONED 10 PERCENT POPS IN GRIDS.

WILL DEFINITELY SEE AN AFFECT ON TEMPERATURES WITH THIS COLD FRONT.
FOR FRIDAY...HIGH TEMPERATURES WILL BE ABOUT 10-20 DEGREES COOLER
THAN THIS AFTERNOON. FOR SATURDAY MORNING...EXPECT SOME FREEZING
TEMPERATURES IN THE NORTH. BASED ON THIS...HAVE GONE AHEAD AND
ISSUED A FREEZE WATCH FOR PORTIONS OF NW GEORGIA. EVEN THOUGH THE NE
COUNTIES ARE EXPECTED TO BE BELOW FREEZING SATURDAY MORNING...THE
FROST/FREEZE PROGRAM DOES NOT START FOR THOSE COUNTIES UNTIL APRIL
15.

11

LONG TERM /SATURDAY THROUGH THURSDAY/...
/ISSUED AT 339 PM EDT THU MAR 26 2015/
EXTENDED MODELS ARE COMING INTO BETTER AGREEMENT AT THE START OF THE
EXTENDED PERIOD. 12Z NAM/GFS SHOWING MOISTURE DIVING ON THE BACKSIDE
OF THE TROF FURTHER TO THE WEST...AND NOT REACHING WEST GA UNTIL
SATURDAY EVENING...MORE IN LINE WITH THE SREF/ECMWF...HAVE KEPT
SLIGHT CHANCE POPS IN 00-06Z SUNDAY BUT EXPECT MAINLY AN INCREASE IN
CLOUDINESS SATURDAY AFTERNOON.

MODELS KEEP NORTHWEST FLOW ALOFT AND CONTINUE TO SHOW COLDEST
TEMPERATURES SUNDAY MORNING....AND WILL NEED TO CONTINUE MONITORING
FOR POSSIBLE FROST/FREEZE.  MADE MINOR CHANGES TO TEMPERATURES WITH
FREEZING LINE A LITTLE FURTHER SOUTH.  STILL NOT COLD ENOUGH TO
BREAK RECORDS PER ATTACHED RECORDS BELOW.

GFS/ECMWF STILL SHOWING DISCREPANCIES IN HANDLING OF FRONT ON
MONDAY AND SYSTEM THROUGH THE END OF THE WEEK. HAVE ONLY TWEAKED
TEMPERATURES THROUGH THIS TIME FRAME WITH PREVIOUS THINKING
INCLUDED BELOW.

ATWELL.

PREVIOUS LONG TERM.../ISSUED 359 AM EDT THU MAR 26 2015/
TEMPERATURE BUST POTENTIAL ALERT FOR SATURDAY AFTERNOON...
PARTICULARLY ACROSS THE WESTERN PORTION OF THE CWA.  GFS AND NAM
START THE PERIOD WITH DEEP TROF ENTRENCHED ACROSS THE REGION AND
BACKSIDE SHORTWAVE DIVING SOUTHEAST AND DEEP MOISTURE MOVING THROUGH
THE MID MS VALLEY.  BOTH GFS AND NAM GUIDANCE SUGGESTING LOW END
RAIN CHANCES WITH THIS FEATURE LATE SAT AM INTO THE AFTERNOON.
GIVEN THE VERY COLD THERMAL PROFILE ACROSS THE AREA...ANY SATURATION
OF THE COLUMN WOULD KEEP TEMPS A GOOD 10 DEGREES BELOW CURRENT
FORECAST AS A RESULT OF ANY PRECIP FALLING THROUGH THE LAYER. ITS A
GOOD THING WE ARE IN LATE MARCH AFTER LOOKING AT THE GFS SOUNDINGS
FOR SATURDAY.  HAVE PUT LOW POPS IN TO ACCOUNT WITH LIGHT RAIN
MENTION...BUT NOT ALL MODELS AS BULLISH WITH THE DEEP MOISTURE AND
BACKSIDE SHORTWAVE AKA SREF AND ECMWF.  FOR NOW..WILL KEEP LOW POP
MENTION AND HOLD TEMPS IN THE 50`S AREAWIDE.  AS AN FYI...RECORD LOW
MAX TEMP AT CSG ON SATURDAY IS 48.

COLDEST MORNING STILL APPEARS TO BE SUNDAY MORNING WITH BEST
RADIATIONAL COOLING AREAWIDE. GENERAL FREEZING LINE RUNNING FROM
NEWNAN TO PEACHTREE CITY TO ATHENS AND POINTS NORTH. WILL CERTAINLY
HAVE TO CONSIDER FROST/FREEZE CONCERNS GIVEN CLEAR SKIES...LIGHT
WINDS...AND HIGHER RH VALUES...EVEN IN AREAS ACROSS THE SOUTH...AS
FROST CAN OCCUR IN AIR TEMPS ABOVE FREEZING.  STILL NOT FORECASTING
RECORD TEMPS BUT WILL CERTAINLY BE WITHIN A FEW DEGREES OF THE
RECORDS AT ALL SITES.

GFS AND ECMWF IN BETTER AGREEMENT TODAY OVER ANOTHER FRONT MOVING
THROUGH THE AREA ON MONDAY.  HAVE PUT RAIN CHANCES IN THE FORECAST
STARTING MONDAY AM...ALBEIT LOW CHANCES WITH NO MENTION OF THUNDER.
MODELS DIVERGE A BIT ON TUESDAY DESPITE HAVING THE SAME GENERAL
NORTHWEST FLOW PATTERN ACROSS THE REGION.  GFS MORE BULLISH WITH
BRINGING A STRONG SHORTWAVE EASTWARD OUT OF TEXAS AND THUS MUCH MORE
AVAILABLE MOISTURE FOR GENERAL SHOWERS/LOW END POPS ACROSS THE AREA.
 ECMWF HAS ALMOST NO ACCOUNTING OF THIS FEATURE THUS PITTING THE
FORECAST BETWEEN A GENERALLY DRY ONE VS A WET FORECAST TUESDAY
THROUGH THURSDAY OF NEXT WEEK.  FOR NOW...HAVE CHANCE POPS IN EACH
DAY AND FAVOR THE GFS AS IT HAS BEEN FAIRLY CONSISTENT WITH THIS
FEATURE FOR SEVERAL DAYS NOW. SHORTWAVE...PER GFS...APPROACHES LATE
WED INTO THU AND THUS POPS WILL INCREASE A BIT MORE.  KEEPING
THUNDER OUT FOR NOW...BUT WILL HAVE TO SEE HOW THIS FEATURE EVOLVES.

STELLMAN

CLIMATE...

RECORDS FOR 03-29

               MAX TEMPERATURE         MIN TEMPERATURE
  STATION      HIGH        LOW         HIGH        LOW
  -------  ----------  ----------  ----------  ----------
   KAHN      85 1928     47 1959     62 1977     25 1887
                                        1907
   KATL      84 1989     43 1894     65 1924     25 1887
                1945
   KCSG      89 2007     52 2001     67 1997     32 1955
                                                    1953
                                                    1948
   KMCN      87 1907     47 1926     67 1924     30 1966


&&

.AVIATION...
06Z UPDATE...
COLD FRONT HAS MADE ITS WAY INTO THE NORTHERN MOST TAF SITES BU
-SHRA CONTINUE EVEN BEHIND THIS FRONTAL BOUNDARY. A MIXED BAG THUS
FAR OF IFR...MVFR AND VFR CIGS ASSOCIATED WITH THIS FEATURE AND
WILL HANDLE WITH SHORT TERM TEMPO TO ACCOUNT FOR THE POTENTIAL
OVC008 THROUGH 10Z. THEREAFTER...SHOULD SEE MVFR CIGS TRANSITION
TO VFR BY MID MORNING AS WINDS INCREASE FROM THE NW TO 15G25KT.

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

DEESE

&&

.PRELIMINARY POINT TEMPS/POPS...
ATHENS          62  34  53  31 /  20   5   0   5
ATLANTA         58  34  51  32 /  10   5   5  10
BLAIRSVILLE     51  27  44  26 /  10  10   5   5
CARTERSVILLE    57  32  50  29 /  10   5   5  10
COLUMBUS        63  38  57  35 /  10   0  10  20
GAINESVILLE     58  32  50  31 /  10   0   0   5
MACON           64  37  56  33 /  30   0   5  10
ROME            56  31  50  28 /  10   5   5  10
PEACHTREE CITY  60  33  53  30 /  10   5  10  20
VIDALIA         68  40  58  35 /  50   5   0   5

&&

.FFC WATCHES/WARNINGS/ADVISORIES...
FREEZE WATCH FROM LATE TONIGHT THROUGH SATURDAY MORNING FOR THE
FOLLOWING ZONES: BARTOW...CATOOSA...CHATTOOGA...DADE...FLOYD...
GORDON...MURRAY...WALKER...WHITFIELD.

&&

$$

SHORT TERM...DEESE
LONG TERM....01
AVIATION...DEESE



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