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Area Forecast Discussion

870
FXUS62 KFFC 041740 AAC
AFDFFC

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE PEACHTREE CITY GA
1240 PM EST WED MAR 4 2015

.PREV DISCUSSION... /ISSUED 1025 AM EST WED MAR 4 2015/

UPDATE...

DENSE FOG IS LIFTING ACROSS THE AREA SO HAVE ALLOWED THAT PRODUCT
TO EXPIRE. ALSO SEEING LESS EVIDENCE IN RADAR AND HI-RES
REFLECTIVITY FORECASTS OF PRECIP PUSHING INTO NORTH GEORGIA
THROUGH THE DAY...SO HAVE CUT BACK ON POPS TODAY AND REDUCED THEM
ACROSS SOUTHERN ZONES TONIGHT. WILL TAKE A GOOD HARD LOOK AT
WINTRY POTENTIAL TOMORROW MORNING WITH THE AFTERNOON PACKAGE.

TDP

PREV DISCUSSION... /ISSUED 632 AM EST WED MAR 4 2015/

PREV DISCUSSION... /ISSUED 345 AM EST WED MAR 4 2015/

SHORT TERM /TODAY THROUGH THURSDAY/...
WEDGE IS ERODING ON ITS WESTERN SIDE THIS MORNING. VSBYS AND CIGS
HAVE GREATLY IMPROVED UP THE AL/GA STATE LINE...AND ESPECIALLY
WHERE WINDS HAVE TURNED SOUTHERLY OR SOUTHWESTERLY. THE FOG IS
SHALLOW...AND CIGS ARE AN OBSCURATION RATHER THAN A CLOUD DECK...SO
CLEARING WILL BE FAIRLY RAPID WHEN IT OCCURS. WILL BE MAKING
ADJUSTMENTS TO THE DENSE FOG ADVISORY WHERE VSBYS HAVE COME UP ABOVE
1/4SM. WILL LIKELY HAVE TO CLEAR ADDITIONAL ZONES BEFORE LEAVING
THIS MORNING AS CONDITIONS IMPROVE.

A COLD FRONT IS STILL ON TRACK TO IMPACT THE CWFA LATER TODAY INTO
THURSDAY. MODELS ARE IN GOOD AGREEMENT WITH THE TIMING OF THE
BOUNDARY AND KEEPING MOST OF THE PRECIP ANAFRONTAL.  IN THE LAST FEW
MODEL RUNS...THE 500MB TROUGH HAS BECOME LESS SHARP OVER THE
CWFA...AND WASHES OUT. IN ADDITION...MODELS HAVE ALSO DELAYED THE
ARRIVAL OF THE COLD AIR BEHIND THE FRONT. THE TIMING OF THE COLD AIR
AT THE SURFACE AND ALOFT IS VERY TRICKY AND MODELS HAVE DEFINITELY
STRUGGLED WITH THIS IN PREVIOUS RUNS. CURRENTLY...THE COLDEST AIR
DOESN`T BEGIN INFILTRATING THE NORTHERN CWFA UNTIL BETWEEN 12Z AND
15Z THU. IF THIS HOLD TRUE...ANY WINTRY MIX UP NORTH WILL BE MOSTLY
DURING THE DAY ON THU RATHER THAN OVERNIGHT WED. HOWEVER...REMEMBER
THAT THE MODELS CONTINUE TO STRUGGLE WITH TEMPS AT THE SURFACE AND
ALOFT...SO NOT A HIGH CONFIDENCE SITUATION FOR THE TIMING OF THE
COLD AIR.

PTYPE WILL ALSO HEAVILY DEPEND UPON THE TIMING OF THE COLD AIR. FOR
THE LAST FEW RUNS...MODEL SOUNDINGS ARE SHOWING RAIN MIXING WITH
SLEET AT TIMES AS THE COLD AIR MOVES INTO THE REGION. THEN...RAIN
MAY SWITCH OVER TO A MIXTURE OF SLEET AND FREEZING RAIN...FINALLY
FINISHING OFF WITH THE POTENTIAL FOR SOME FREEZING DRIZZLE. IF THE
COLD AIR IS DELAYED ANY FURTHER INTO THU...THEN THE POTENTIAL FOR AN
IMPACTFUL AMOUNT OF WINTRY MIX BECOMES LESS AND LESS. FOR NOW...NOT
EXPECTING MUCH SLEET ACCUMULATION...AMOUNTS SHOULD BE LESS THAN A
QUARTER OF AN INCH. DO THINK LIGHT ICING WILL BE AN ISSUE...BUT
AMOUNTS SHOULD BE A TENTH OF AN INCH OR LESS IN MOST LOCALES.
AGAIN...THE PTYPE IS HEAVILY DEPENDENT UPON THE TEMPERATURES ALOFT
AND AT THE SURFACE...SOMETHING THE MODELS HAVE BEEN STRUGGLING
WITH...SO CONFIDENCE IS LOW TO MEDIUM IN ACCUMULATIONS. THE
ACCUMULATION ISSUE WILL ALSO BE COMPLICATED BY WARM GROUND TEMPS.

TEMPS TODAY ARE EXPECTED TO BE WELL ABOVE NORMAL AND EVEN POSSIBLY
REACH THE LOWER 80S IN THE FAR SOUTH. A FEW BREAKS IN THE CLOUDS ARE
POSSIBLE ALONG AND WEST OF THE ERODING EDGE OF THE WEDGE. TEMPS ON
THURSDAY SHOULD BE NEARLY STEADY IN THE NORTH...AND SHOULD FALL
THROUGH THE AFTERNOON ELSEWHERE.

NLISTEMAA

LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/...
PERIOD STARTS OUT COOL BUT MOSTLY DRY AS PRECIPITATION EXITS THE
FORECAST AREA LATE IN THE DAY THURSDAY...LINGERING ONLY IN THE
SOUTHEAST INTO THURSDAY EVENING. UPPER-LEVEL AND SURFACE PATTERNS
ARE NOT TYPICAL OF SUCH A STRONG SHOT OF COLDER AIR THIS LATE IN THE
SEASON WITH NEARLY ZONAL FLOW ALOFT AND RAPIDLY WEAKENING SURFACE
PRESSURE GRADIENT...BUT UPSTREAM REGION DOES HAVE GOOD RESIDUAL SNOW
COVER. I AM INCLINED BACK OFF A LITTLE ON COLD TEMPERATURES THURSDAY
NIGHT...GENERALLY STAY CLOSER TO THE NAM MOS NUMBERS WHICH ARE STILL
WELL BELOW SEASONAL NORMALS. THE REMAINDER OF THE EXTENDED FORECAST
PERIOD IS RELATIVELY QUIET IF POTENTIALLY WET AT TIMES. UPPER FLOW IS
WEAK AND GENERALLY ZONAL THROUGH THE WEEKEND WITH WEAK SURFACE HIGH
PRESSURE OVER THE SOUTHEASTERN U.S. LARGER SCALE FEATURES REMAIN
RELATIVELY SIMILAR BETWEEN THE GFS AND ECMWF THROUGH THE MAJORITY OF
THE EXTENDED PERIOD...BUT ALSO REMAIN SOMEWHAT VAGUE ON BOTH
CONCERNING ANY ENHANCED LIFT FOR RAIN CHANCES. GFS LIFTS WEAK SHORT
WAVE THROUGH SUNDAY INTO MONDAY WHILE ECMWF DELAYS THE WEAK SHORT
WAVE UNTIL THE MONDAY-TUESDAY PERIOD. FOR NOW I DO NOT HAVE ENOUGH
CONFIDENCE IN EITHER SCENARIO TO FOCUS ON ANY SPECIFIC SOLUTION. PLAN
ON RUNNING WITH SEASONAL TEMPERATURES AND CHANCE POPS AT BEST SUNDAY
THROUGH THE END OF THE FORECAST.

20

&&

.AVIATION...
18Z UPDATE...
MVFR TO PATCHY VFR CIGS THIS AFTERNOON AND EXPECT LIFTING/CLEARING
TREND TO CONTINUE FOR A FEW HOURS. CIGS SHOULD DROP AGAIN BACK TO
MVFR AFTER 00Z /CURRENT TIMING FOR ATL IS 02Z/ WITH IFR DEVELOPING
BY 06Z. SEE NO REASON TO NOT GO LIFR AGAIN FOR NORTHERN TAFS WITH
ABUNDANT MOISTURE AND HAVE CIGS LIFR THROUGH MOST OF THURSDAY
MORNING...WITH SLOW IMPROVEMENT TO IFR AND EVENTUALLY MVFR /LATE
IN THE DAY/. WINDS SSW TO SW AROUND 10KT WITH LOW-END GUSTS THIS
AFTERNOON...BETWEEN 5-10KT OVERNIGHT AND SHIFTING MORE W TO WNW.
WINDS SHIFT NW AND BACK ABOVE 10KT AFTER FROPA LATE THURSDAY WITH
LOW-END GUSTS.

//ATL CONFIDENCE...18Z UPDATE...
HIGH ON CIG/VSBY TRENDS...MEDIUM ON ACTUAL VALUES.
MEDIUM-HIGH ON WINDS.

TDP

&&

.PRELIMINARY POINT TEMPS/POPS...
ATHENS          73  60  62  32 /  10  60  90  30
ATLANTA         71  53  55  30 /  10  90 100  20
BLAIRSVILLE     65  45  46  26 /  40 100 100  10
CARTERSVILLE    72  42  44  26 /  30 100 100  10
COLUMBUS        76  63  64  35 /  10  70  80  30
GAINESVILLE     68  54  56  30 /  20  90 100  20
MACON           77  63  66  37 /  10  40  70  30
ROME            71  40  42  24 /  40 100 100  10
PEACHTREE CITY  73  57  58  30 /  10  80  90  20
VIDALIA         81  62  77  41 /  10  10  60  40

&&

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

$$



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