Area Forecast Discussion
Issued by NWS Atlanta, GA

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FXUS62 KFFC 011145
AFDFFC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PEACHTREE CITY GA
645 AM EST SUN FEB 1 2015

.PREV DISCUSSION... /ISSUED 413 AM EST SUN FEB 1 2015/

..LIGHT SNOW REMAINS POSSIBLE FOR MOUNTAINS BUT ACCUMULATIONS
LIMITED...
..THUNDERSTORMS NOW POSSIBLE WESTERN AND SOUTHERN SECTIONS
TONIGHT...

SHORT TERM /TODAY THROUGH MONDAY/...
HIGH PRESSURE NOW CENTERED JUST OFFSHORE THE CAROLINAS ALLOWING
FOR A RETURN FLOW OVER THE LOCAL AREA. THUS FAR THIS HAS ONLY
RESULTED IN A SLIGHT INCREASE IN LOW LEVEL MOISTURE AND NOT LOW
CLOUDS. INSTEAD...MID AND UPPER LEVELS CONTINUE TO DOMINATE WITH
ABUNDANT CLOUD COVER THE RESULT OF A STRONG SOUTHERN BRANCH TO THE
JET FROM THE EASTERN PACIFIC THROUGH MEXICO AND TEXAS AND INTO THE
DEEP SOUTH. HAVE BEEN SEEING RETURNS ON REGIONAL RADAR PRETTY MUCH
ALL NIGHT BUT NOTHING REACHING THE GROUND DEWPOINTS REMAINING IN
THE 20S TO LOWER 30S AT BEST ACROSS THE AREA.

FOR TODAY...IMPULSE IN MID LEVEL FLOW FOR THE NORTHERN SECTIONS
WILL ACT TO MOISTEN THE ATMOSPHERE BELOW BUT AT LEAST THROUGH MID
MORNING EXPECT CONTINUED VIRGA FROM A MAINLY MID CLOUD DECK. MORE
SUBSTANTIAL IMPULSE MOVES IN FROM ALABAMA THIS AFTERNOON AND BY
THIS TIME ALL AREAS WILL BE CONDUCIVE TO SEEING LIGHT RAIN AS
DEWPOINTS RISE INTO THE LOWER TO MID 40S. BETWEEN 18Z AND
00Z...CONTINUED MOISTURE INCREASE AND LIFT FROM EMBEDDED
SHORTWAVES IN MEAN FLOW...NOT TO MENTION ADIABATIC OMEGA
INFLUENCES IS ENOUGH TO WARRANT CATEGORICAL POPS IN THE GRIDS.

WITH FURTHER NORTHWARD PROGRESSION OF SYNOPTIC FEATURES WITH THIS
SYSTEM THE PAST FEW DAYS...SEEING LOCALLY A RESPONSE IN THE SURGE
OF DEWPOINTS LATE THIS EVENING INTO THE OVERNIGHT HOURS. NOW
SEEING MID 50S TO AROUND 60 DEGREE VALUES MOVING ALL THE WAY UP TO
ROME AND EXTENDING ACROSS THE METRO AND ALL OF MIDDLE GEORGIA.
GIVEN ABUNDANCE OF CLOUD COVER AND PRECIP...NOT SURE HOW MUCH
ACTUAL SURFACE CAPE WE WILL BE ABLE TO GENERATE BUT STRONG
ISENTROPIC FLOW MAY BE ABLE TO ALLOW FOR AT LEAST SOME ELEVATED
CONVECTION AND HAVE ADDED THUNDER TO A GOOD PORTION OF THE AREA
WITH THIS ISSUANCE. FURTHER SOUTH FROM COLUMBUS TO MACON...HIGHER
LIKELIHOOD OF SURFACE BASED INSTABILITY BUT SHOULD BE WEAK IN
NATURE. 925MB WINDS INCREASE TO 45 TO 50 KTS SUN NIGHT INTO MONDAY
MORNING OVER THESE SAME AREAS SO CONCERNED THERE COULD BE SOME
STRONG DAMAGING WINDS OVER THESE AREAS DESPITE THE APPARENT LACK
OF INSTABILITY. WILL NEED TO BE WATCHED CLOSELY AS HELICITY VALUES
ARE ALSO SUFFICIENT FOR AN ISOLATED SPINUP AHEAD OF THE MAIN LINE
SHOULD ENHANCED INSTABILITY BE REALIZED.

WITH THE SYSTEM FURTHER NORTH...WE ALSO SEE THAT THE SNOW
POTENTIAL HAS DECREASED WITH THIS RUN. THERE IS STILL AN
OPPORTUNITY FOR MUCH OF THE HIGHER ELEVATIONS TO SEE A BRIEF
SWITCHOVER AND FOR SOME ACCUMULATING SNOW OVER THE NE
MOUNTAINS...BUT CHANCES AND AMOUNTS ARE LESS. WILL GENERALLY GO
WITH A HALF AN INCH OR LESS OVER THE HIGHER ELEVATIONS OF THE NE
MOUNTAINS FOR NOW BUT CANNOT COMPLETELY RULE OUT ISOLATED HIGHER
AMOUNTS AT THE HIGHEST PEAKS. OF MORE CONCERN IS THE RAPID DROP IN
TEMPS AS PRECIP EXITS. BRASSTOWN BALD MODEL COBB SHOWS TEMPS
DROPPING FROM 44 TO 25 IN JUST 2 HOURS AS PRECIP HANGS ON. FEEL
THIS COULD BE THE CASE ACROSS MUCH OF THE EXTREME NORTHERN TIER
HIGHER ELEVATIONS AND BLACK ICE WILL ONCE AGAIN BE OF CONCERN.
WINDS WILL HELP AS THEY GUST ALL NIGHT SO SHOULD BE A FAIRLY SHORT
LIVED EVENT FOR MOST.

DEESE

LONG TERM /MONDAY NIGHT THROUGH SATURDAY/...
FOLLOWING THE ACTIVE SHORT TERM PERIOD...HIGH PRESSURE RETURNS TO
THE AREA TUESDAY. MODELS CONTINUE TO DELAY THE ONSET OF THE
PRECIPITATION WEDNESDAY...AND HAVE LARGELY BACKED OFF ON
INTRODUCING POPS TO THE AREA UNTIL LATE WEDNESDAY. ECMWF AND GFS
SOLUTIONS CONTINUE TO FLIP-FLOP AND SO HAVE TRIED TO AVOID SIDING
WITH ONE MODEL OR THE OTHER...AND HAVE GONE WITH MORE OF AN
OVERALL BLEND...TRENDING TOWARDS THE PREVIOUS FORECAST.
TEMPERATURES THURSDAY AND FRIDAY MORNINGS WILL BE COLD ENOUGH TO
SUPPORT WINTRY PRECIP AS MOISTURE REMAINS ACROSS THE STATE. FOR
NOW...THURSDAY MORNING CHANCES LOOK TO BE ISOLATED TO THE NORTH
GEORGIA MOUNTAINS...WHILE FRIDAY MORNING CHANCES EXTEND A WINTRY
MIX INTO THE ATLANTA METRO AREA. UNCERTAINTY WITH THIS SYSTEM IS
STILL VERY HIGH AND EXPECT THIS FORECAST TO CHANGE SOMEWHAT AS MID
WEEK APPROACHES.

31

AVIATION...
12Z UPDATE... TRANQUIL START TO THE TAF PERIOD BUT THINGS WILL
CHANGING QUICKLY AHEAD OF THE NEXT APPROACHING COLD FRONT. LOW
LEVEL MOISTURE WILL BE THE FIRST THING ON THE INCREASE WITH MVFR
DECK MOVING IN FROM SOUTH TO NORTH THROUGH MID MORNING SO
AFFECTING MCN AND CSG FIRST AND THEN THE ATL SITES. -RA AND IFR
CIGS IN THE OFFING FOR THE AFTERNOON WITH VSBY DROPPING AS WELL TO
AROUND 2SM AT MOST SITES. WINDS SHIFT WITH FRONT GETTING NEARER
AROUND 05Z TO THE SW AND INCREASING TO 12 KTS WITH LOW END GUSTS
POSSIBLE AS WELL.

//ATL CONFIDENCE...12Z UPDATE...
MEDIUM ON MVFR CIG TIMING.
HIGH ON REMAINING ELEMENTS.

DEESE

&&

.PRELIMINARY POINT TEMPS/POPS...
ATHENS          57  46  47  25 /  40 100  40   0
ATLANTA         56  41  42  27 /  70 100  40   0
BLAIRSVILLE     46  36  39  22 /  70 100  40   0
CARTERSVILLE    55  39  41  23 /  80 100  30   0
COLUMBUS        63  47  48  28 /  60 100  20   0
GAINESVILLE     51  41  43  26 /  70 100  40   0
MACON           65  51  52  26 /  30  90  40   0
ROME            54  38  41  22 /  80 100  20   0
PEACHTREE CITY  59  43  45  24 /  60 100  30   0
VIDALIA         67  54  57  32 /  20  60  40   5

&&

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

$$

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


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