Area Forecast Discussion
Issued by NWS Atlanta, GA

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FXUS62 KFFC 131937
AFDFFC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PEACHTREE CITY GA
237 PM EST SAT FEB 13 2016

.SHORT TERM /TONIGHT THROUGH SUNDAY NIGHT/...
SHORT TERM FORECAST CONTINUES TO BE A CHALLENGE WITH IMPACTFUL
WINTRY PRECIPITATION EXPECTED ACROSS NORTH GEORGIA. UPPER LEVEL
DISTURBANCE WILL INTERACT WITH COLD AND DRY CONDITIONS ACROSS THE
AREA TO PRODUCE A WINTRY MIX OVER PORTIONS OF NORTH GEORGIA.
ALTHOUGH MODELS HAVE SLOWED THE ONSET TIMING SLIGHTLY BY AN HOUR OR
SO...CONSENSUS IS THAT PRECIPITATION WILL BEGIN AS SNOW THIS
MORNING...THEN TRANSITION TO FREEZING RAIN/SLEET AND THEN TRANSITION
TO ALL SNOW IN THE NE MOUNTAINS BY THE AFTERNOON. ACCUMULATING
WINTRY MIX IS EXPECTED AS FAR SOUTH AS PORTIONS OF THE NORTHERN
ATLANTA SUBURBS...BUT STILL COULD SEE SOME NON-ACCUMULATING MIX AS
FAR SOUTH AS I-20. ALREADY SEEING SOME LIGHT RETURNS ON RADAR ACROSS
AL/NORTHERN GEORGIA...BUT SO FAR NOTHING REACHING THE GROUND.

MODELS CONTINUE TO SUGGEST THIS TO BE AN OVERALL LOW QPF
EVENT...WITH LIQUID EQUIVALENT ONLY A QUARTER INCH OR LESS. WPC WWD
GUIDANCE HAS BACKED OFF SOMEWHAT ON SNOWFALL TOTALS...BUT HAS SPREAD
THE ACCUMULATING FREEZING RAIN AMOUNTS FARTHER SOUTH. GIVEN THE
TIMING OF THE PRECIPITATION ONSET AND THE EXPECTED WARMING
TEMPERATURES /PARTICULARLY ACROSS THE METRO AREA/ HAVE OPTED NOT TO
DEVIATE TOO FAR FROM THE PREVIOUS SNOW/ICE AMOUNTS PREVIOUSLY
FORECAST...A LITTLE MORE CONSERVATIVE IN AREAL COVERAGE THAN THE WWD
ICE GRID.

THE WINTER STORM WARNING AND THE WINTER WEATHER ADVISORY CONTINUE
WITH NO CHANGES MADE TO THE TIMING OR AREA. STILL ANTICIPATE UP TO 2-
2.5 INCHES OF SNOW IN THE WSW /PARTICULARLY IN THE NE GA MOUNTAINS/
AND UP TO A TENTH OF AN INCH OF ICE. IN THE ADVISORY AREA UP TO 1
INCH OF SNOW AND A TENTH OF AN INCH OF ICE CAN BE EXPECTED. WITH
COLD ANTECEDENT CONDITIONS...IMPACTS ARE EXPECTED AT ONSET OF THE
PRECIPITATION. HAVE ALSO CONTINUED THE SPECIAL WEATHER STATEMENT FOR
SEVERAL COUNTIES JUST SOUTH OF THE ADVISORY AREA TO INDICATE
POTENTIAL FOR WINTRY PRECIPITATION MIXED WITH RAIN.

THERE REMAINS SEVERAL UNCERTAINTIES WITH THE FORECAST THAT WILL NEED
TO BE MONITORED AS THE EVENT UNFOLDS. THE WEAKENING RIDGE AND
EROSION OF THE ASSOCIATED LOW LEVEL INVERSION WILL PLAY A KEY ROLE
IN DURATION OF WINTER PRECIP. THERMODYNAMIC TRENDS WILL STILL NEED
TO BE WATCHED FOR WETBULBING/EVAPORATIVE COOLING EFFECTS AND IF IT
DELAYS THE TRANSITION TO OTHER P-TYPES. LINGERING FREEZING
TEMPERATURES INTO THE OVERNIGHT HOURS COULD ALLOW FROZEN PRECIP TO
CONTINUE AND INCREASE BLACK ICE THREAT.

STAY TUNED AS THE FORECAST CONTINUES TO EVOLVE AS THE EVENT UNFOLDS.

ALTHOUGH THE PRECIPITATION POTENTIAL DIMINISHES SOMEWHAT
OVERNIGHT...ALL RAIN WILL RETURN TO THE AREA THURSDAY AND INTO THE
INITIAL EXTENDED FORECAST PERIODS. ANTICIPATE THAT BY MID MORNING
THURSDAY ALL OF NORTH AND CENTRAL GEORGIA SHOULD BE SEEING ABOVE-
FREEZING TEMPERATURES.

31


.LONG TERM /MONDAY THROUGH SATURDAY/...
AGAIN A COMPLICATED FORECAST FOR THE EARLY PART OF THE LONG TERM
WITH JUST MINOR CHANGES FROM THE PREVIOUS FORECAST. THE BIGGEST
DIFFERENCE IS THE TIMING OF THE ONSET OF THE PRECIP. ALL MODELS ARE
DELAYING THE ONSET FROM THE PREVIOUS FORECAST. THIS WILL PLAY A ROLE
IN THE AMOUNT OF COOLING IN THE WEDGE AREA. THE SURFACE HIGH WILL BE
TRANSIENT AND ALSO THE UPPER SUPPORT FOR THE WEDGE WILL WEAKEN
SUNDAY NIGHT AND MONDAY. THEREFORE THE ONLY REAL SUPPORT FOR HOLDING
THE WEDGE AND COLDER AIR WILL BE EVAP COOLING FROM THE
RAIN...HOWEVER THIS WILL BE DELAYED BY A FEW HOURS WHICH WILL BE
ENOUGH FOR TEMPS TO RISE A COUPLE DEGREES HIGHER THAN PREVIOUSLY
EXPECTED. JUST THESE COUPLE OF DEGREES COULD MAKE THE DIFFERENCE
BETWEEN ZR AND R. AT THIS POINT IT IS TOO FAR OUT TO SAY ONE WAY OR
THE OTHER AND THEREFORE WILL MAINTAIN A PRETTY CONSISTENT FORECAST
WITH P-TYPE. IT WILL START WITH A R/ZR/S MIX ACROSS NORTH GA
...TRANSLATING TO A R/ZR MIX ACROSS NORTHEAST GA WITH RAIN OVER THE
REST OF THE CWA MONDAY AFTERNOON. BY 00Z TUE...THERE COULD BE
ISOLATED POCKETS OF ZR...BUT MOST AREAS SHOULD BE ALL RAIN. THIS IS
GOOD AS THE HEAVY RAIN WILL BE MOVING INTO THE CWA AFTER 00Z TUE.
HAVING SAID THAT...WILL ISSUE A WINTER STORM WATCH FROM 06Z MON TO
00Z TUE FOR MUCH OF NORTHEAST GA. THIS WILL INCLUDE THE NORTH AND
NORTHEAST ATL METRO AREAS BUT NOT THE CITY OF ATL. AHN IS ALSO NOT
IN THE WATCH.

THE SYSTEM WILL PULL RAPIDLY OUT OF THE CWA LATE MONDAY
NIGHT/TUESDAY...AND THERE COULD BE A BRIEF MIX OF R/S IN THE NORTH
TUESDAY MORNING BUT NO ADDITIONAL ACCUMULATION EXPECTED. A FAST
MOVING UPPER SYSTEM WILL BE PULLING FURTHER NORTH BUT THE TAIL END
COULD MOVE ACROSS EXTREME NORTH GA TUESDAY NIGHT AND THIS WILL BRING
A CHANCE OF R/S...BUT NO SIGNIFICANT ACCUMULATION IS EXPECTED AT
THIS TIME.

TEMPS WILL WARM RAPIDLY AFTER THE TUESDAY NIGHT SYSTEM WITH MOST
AREAS INTO THE 60S BY THURSDAY.

17

&&

.AVIATION...
18Z UPDATE...
VFR CONDITIONS EXPECTED THROUGH THE PERIOD. GUSTS WILL DIMINISH
INTO THE LATE AFTERNOON...WITH 7KT OR LESS OVERNIGHT. WINDS SHIFT
FROM THE NNW TO THE NE AROUND 06Z...THEN CONTINUE TO SHIFT TO THE
SE BY 18-21Z. CLOUDS WILL BUILD INTO THE REGION BY SUNDAY
MORNING...WITH BKN-OVC VFR THROUGH THE DAY.

//ATL CONFIDENCE...18Z UPDATE...
HIGH CONFIDENCE ON ALL ELEMENTS.

31

&&

.PRELIMINARY POINT TEMPS/POPS...
ATHENS          22  42  30  41 /   0   5  40  80
ATLANTA         24  44  34  44 /   0   5  40  90
BLAIRSVILLE     19  35  28  36 /   0  20  80 100
CARTERSVILLE    21  44  33  43 /   0  10  60 100
COLUMBUS        27  52  39  59 /   0   5  20  80
GAINESVILLE     21  39  30  36 /   0   5  50  90
MACON           23  50  36  59 /   0   5  20  80
ROME            20  44  34  43 /   0  20  80 100
PEACHTREE CITY  21  47  33  48 /   0   5  30  90
VIDALIA         29  49  39  65 /   0   5  10  70

&&

.FFC WATCHES/WARNINGS/ADVISORIES...
WINTER STORM WATCH FROM LATE SUNDAY NIGHT THROUGH MONDAY EVENING
FOR THE FOLLOWING ZONES: BANKS...BARROW...CHEROKEE...DAWSON...
FANNIN...FORSYTH...GILMER...GWINNETT...HALL...JACKSON...
LUMPKIN...MADISON...MURRAY...PICKENS...TOWNS...UNION...WHITE.

&&

$$

SHORT TERM...31
LONG TERM....17
AVIATION...31


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