Area Forecast Discussion
Issued by NWS Atlanta, GA

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FXUS62 KFFC 281937
AFDFFC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PEACHTREE CITY GA
337 PM EDT TUE APR 28 2015

.SHORT TERM /TONIGHT THROUGH WEDNESDAY NIGHT/...

RAINFALL HAS BEEN SLOW TO MATERIALIZE TODAY BASED ON WHAT
YESTERDAYS MODELS HAD PROJECTED. THE LIKELY CULPRIT WAS THE STRONG
MCS THAT SHOT SE ACROSS THE EASTERN GULF AND INTO SOUTH
FLORIDA...KEEPING MOST OF THE AVAILABLE MOISTURE AND ENERGY WELL
SOUTH OF THE LOCAL AREA. ANOTHER CLUSTER OF THUNDERSTORM HAS
FORMED ALONG THE WARM FRONT OVER THE NORTHERN GULF AND WILL POSE
ADDITIONAL FORECAST CHALLENGES FOR THE EVENING PERIOD. IN ADDITION
TO A LACK OF RAIN OVER SW ZONES...MOSTLY SUNNY CONDITIONS HAVE
TAKEN HOLD OVER MUCH OF NORTH AND EAST CENTRAL GEORGIA ALLOWING
FOR TEMPERATURES WARMER THAN MODEL PROJECTIONS AS WELL.

GIVEN ADIABATIC PROFILE THAT SETS UP THIS EVENING WITH ADIABATIC
OMEGA BECOMING MAXIMIZED BETWEEN 00Z AND 06Z...FEEL WE WILL
EVENTUALLY SEE LIKELY TO CATEGORICAL RAIN COVERAGE WITH ACTIVITY
LIKELY DEVELOPING RIGHT ON TOP OF US AS OPPOSED TO ADVECTING IN
ALTHOUGH THERE WILL BE THAT COMPONENT AS WELL. DIFFLUENCE ALOFT
DEVELOPS AS WELL WHICH SHOULD AID IN OVERALL COVERAGE BUT STILL
EXPECT INTENSITY TO FALL MORE IN LINE WITH JUST LIGHT RAIN. WE DO
GET SOME 35 TO 40 KNOT ISENTROPIC FLOW LATE TONIGHT AND POSSIBLE
TO SEE SOME ELEVATED CONVECTION WITH THIS PROFILE SO HAVE KEPT
-TSRA MENTION FOR THE EXTREME SOUTHERN ZONES.

LOW PASSES OFF THE COAST OF GEORGIA WHICH IS FURTHER SOUTH THAN
PREVIOUS RUNS AND RESEMBLES MORE OF A MID WINTER TYPE PATTERN THAN
SPRING. WE ACTUALLY GET GOOD WRAP AROUND ON THE BACK SIDE OF THIS
SYSTEM AND WILL KEEP LOW END CHANCE POPS FOR THE NORTHERN TIER
THROUGH WED EVENING. MAJORITY OF THE COLD CORE COMES LATER IN THE
EXTENDED AND THAT IS WHEN BEST TSRA CHANCES RETURN SO JUST KEPT
SHRA IN THE GRIDS FOR THIS TAIL END OF THE SHORT TERM PERIOD.

DEESE


.LONG TERM /THURSDAY THROUGH TUESDAY/...

ONLY MINOR ADJUSTMENTS MADE TO THE EXTENDED FORECAST GRIDS WITH THIS
CYCLE. MAIN CHANGE WAS TO PUT ISOLATED THUNDER BACK INTO THE GRIDS
FOR THURSDAY AFTERNOON AND EVENING WITH THE COLD AIR ALOFT ASSOCIATED
WITH THE UPPER LOW DIGGING INTO THE SOUTHERN APPALACHIANS. PLEASE SEE
THE PREVIOUS LONG TERM FORECAST DISCUSSION BELOW.

20


PREVIOUS LONG TERM FORECAST DISCUSSION /WEDNESDAY NIGHT THROUGH
MONDAY/...

WHILE THE CENTER OF THE SFC LOW WILL BE EAST OF THE CWA AT THE START
OF THE LONG TERM...THE AREA IS STILL UNDER THE INFLUENCE OF THE
UPPER LEVEL FEATURE. THIS WILL ALLOW FOR THE BULK OF THE
PRECIPITATION TO HAVE ENDED BUT STILL SOME RAIN POTENTIAL WITH THE
UPPER LEVEL LOW LINGERING IN THE EAST. THE GFS KEEPS THE PARENT
UPPER LOW NORTH OF THE CWA THURSDAY NIGHT AS IT DIVES INTO THE
CAROLINAS BUT THE ECMWF BRINGS IT FURTHER SOUTH INTO GA AND THUS
BRINGS A SECOND WAVE OF PRECIPITATION INTO THE CWA THURSDAY NIGHT.
HAVE COMPROMISED BETWEEN THE TWO SOLUTIONS IN THE FORECAST.
INSTABILITY IS LACKING IN THE LONG TERM WITH THIS SYSTEM SO HAVE
KEPT OUT THE MENTION OF THUNDERSTORMS.

THE UPPER LEVEL LOW MOVES INTO THE ATLANTIC LATER ON FRIDAY. AS THIS
OCCURS...THE UPPER LEVEL FLOW BECOMES NW WHILE HIGH PRESSURE BUILDS
IN AT THE SFC. THE GFS BRINGS A WEAK WAVE ACROSS THE EAST ON SUNDAY
BRINGING PRECIP BACK TO NORTH GEORGIA BUT ECMWF ISNT PICKING UP ON
THIS. HAVE NOT INCLUDED IT IN THE FORECAST AS THE DEPICTION IN THE
GFS LOOKS A LITTLE OFF WITH HOW IT HANDLES THE FEATURE. WITH THE
EXCEPTION OF MAYBE A SMALL CHANCE OF RAIN WITH THIS WAVE THE GFS
IS PICKING UP ON...THE WEATHER SHOULD REMAIN DRY FOR THE WEEKEND
AND INTO MONDAY.

11

&&

AVIATION...
18Z UPDATE...
CHALLENGING FORECAST CYCLE AS COMPLEX OF THUNDERSTORMS WHICH RACED
SOUTHWARD ALONG THE GULF COAST AND INTO FLORIDA HAS IMPACTED WHAT
WE WILL EXPERIENCE LOCALLY AT THE TERMINALS. THE SHORT OF IT IS
THAT WE SHOULD HAVE A DELAYED ONSET OF REDUCED CIG AND VSBY AS
WELL AS RAIN CHANCES COMPARED TO THAT PREVIOUSLY ADVERTISED.
HAVE PUSHED BACK MVFR AND IFR CONDITIONS BY SEVERAL HOURS BUT ONCE
THEY ARE HERE LOOKS LIKE THEY ARE HERE TO STAY WITH THE WORST
CONDITIONS MID MORNING WED THROUGH THE AFTERNOON HOURS.

//ATL CONFIDENCE...18Z UPDATE...
MEDIUM ON MVFR AND IFR ONSET TIME.
HIGH ON REMAINING ELEMENTS.

DEESE

&&

.PRELIMINARY POINT TEMPS/POPS...
ATHENS          52  59  48  70 /  90  90  40  30
ATLANTA         52  59  47  69 /  90  90  30  20
BLAIRSVILLE     48  60  47  63 /  80  90  40  50
CARTERSVILLE    53  62  48  68 /  90  90  30  30
COLUMBUS        57  65  51  72 /  90  70  10  10
GAINESVILLE     51  57  48  67 /  90  90  40  40
MACON           54  60  49  72 / 100  90  20  10
ROME            53  65  48  69 /  90  90  30  30
PEACHTREE CITY  54  60  46  70 /  90  90  20  20
VIDALIA         59  65  56  72 / 100 100  30  10

&&

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

$$

SHORT TERM...DEESE
LONG TERM....20
AVIATION...DEESE



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