Ice Storm in Georgia, December 15, 2005

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE PEACHTREE CITY GA
636 PM EST WED DEC 14 2005

.UPDATE...WITH WET BULB ZERO TEMPERATURES ALREADY BELOW FREEZING
OVER A GOOD PORTION OF THE NORTH AND NORTHEAST...WOULD FEEL BETTER
IF WE HAD MORE WIDESPREAD ADVISORIES OR WARNINGS FOR POSSIBLE
FREEZING RAIN. MOST OF THE PRECIP STILL BACK IN ALABAMA...BUT 18Z
NAM SHOWS PRECIP SPREADING QUICKLY INTO GEORGIA THIS EVENING. WITH
NO SIGN OF ANY RISE IN DEW POINTS CURRENTLY...AS PRECIP BECOMES
MORE STEADY SHOULD SEE A TEMPERATURE DROP...WHICH WOULD ONLY TAKE
A FEW DEGREES TO REACH FREEZING SINCE MOST TEMPERATURES ALREADY IN
THE MID 30S. WILL UPGRADE THE ADVISORY AREA TO AN ICE STORM
WARNING AS THIS AREA SHOULD REACH FREEZING MORE QUICKLY AND HAVE
LONGER DURATIONS. WILL PUT UP AN ADVISORY IN SOME COUNTIES OF
NORTH AND NORTHEAST SURROUNDING THE WARNING AREA FOR SOME SLEET
AND FREEZING RAIN...BUT WITH GROUND TEMPERATURES ABOVE
FREEZING...ANY ACCUMULATION SHOULD BE IN TREES AND POWERLINES.
HOWEVER DO NOT EXPECT ENOUGH DURATION IN THIS AREA TO CAUSE PROBLEMS.

&&

.PREV DISCUSSION... (ISSUED 550 PM EST WED DEC 14 2005)

SHORT TERM...(TONIGHT THROUGH FRIDAY NIGHT)
CAD WEDGE HAS BEEN STRENGTHENING THROUGH THE DAY AS LOWER DEWPOINTS
HAVE FILTERED IN FROM THE NORTHEAST. TEMPERATURES AND DEWPOINTS
UPSTREAM ARE A BIT WORRISOME...ESPECIALLY GIVEN THE POTENTIAL FOR
EVAPORATIVE COOLING. SOME PRECIPITATION HAS ALREADY BEGUN ACROSS THE
NORTHERN HALF OF THE CWA...WE HAVE RECEIVED SCATTERED REPORTS OF
LIGHT SLEET AND SNOW FLURRIES THROUGH THE LATE MORNING AND EARLY
AFTERNOON HOURS...NOT SURPRISING GIVEN THE PROFILE AND THE EXPECTED
EVOLUTION OF THE ATMOSPHERE THROUGH THE DAY. THIS WILL CONTINUE
THROUGH THE REST OF THE AFTERNOON AND INTO THE EVENING...WITH
TEMPERATURES STEADY FOR A WHILE THEN SLOWLY DECREASING.

DEWPOINT DEPRESSIONS IN NORTHEAST GEORGIA ARE HIGH ENOUGH THAT
EVAPORATIVE COOLING MAY QUICKLY ALLOW TEMPERATURES TO FALL TO THE
FREEZING MARK AGAIN. TEMPS SHOULD THEN HOVER NEAR THE FREEZING LEVEL
MOST OF THE NIGHT IN THE LEE OF THE MOUNTAINS...WHILE FOR MOST OF
THE REST OF THE AREA TEMPS SHOULD REMAIN ABOVE FREEZING. EXACT
TEMPERATURES WILL BE DIFFICULT TO PINPOINT AND WILL DEPEND ON ONSET
OF PRECIPITATION...HOW LONG IT TAKES TO REACH SATURATION...AND HOW
WARM TEMPERATURES ACTUALLY GET TODAY...AMONG OTHER THINGS.
MEANWHILE...PRECIPITATION SHOULD BEING IN EARNEST THIS EVENING AND
EARLY TONIGHT. OF COURSE...THE FIRST BIT OF QPF /PERHAPS NOT QUITE
THE TYPICAL QUARTER OF AN INCH OR SO/ WILL GO INTO EVAPORATIVE
COOLING. MOST OF THE PRECIP SHOULD BE RAIN...BUT WOULD NOT BE
SURPRISED TO SEE A CONTINUED MIX ACROSS THE AREA...BUT ANYTHING THAT
DOES FALL AS FREEZING OR FROZEN PRECIPITATION WILL MELT AND NO
IMPACTS WILL BE FELT...EXCEPT IN NORTHEAST GEORGIA. AN UPDATED SPS
WILL BE ISSUED TO DISCUSS THE SITUATION.

ALSO...WILL ISSUE A WINTER WEATHER ADVISORY FOR A FEW COUNTIES IN
THE CLIMATOLOGICALLY PREFERRED CAD AREA. WITH TEMPERATURES HOVERING
NEAR FREEZING...AND WBZS BELOW FREEZING UNTIL NEAR 12Z THURSDAY...
THE GRADIENT OF WBZS BETWEEN THE SURFACE AND TREETOP LEVEL WOULD BE
PLENTY TO ALLOW FOR SOME MINOR ACCUMULATIONS OF ICE ON TREES AND
POWERLINES. PRE-EXISTING WARM GROUND TEMPERATURES WOULD PRECLUDE ANY
ROAD OR TRAVEL PROBLEMS FOR THE MOST PART...EXCEPT PERHAPS ON A FEW
EXPOSED BRIDGES AND OVERPASSES. NOMOGRAM THICKNESSES FOR THE GVL
AREA /AND NATURALLY AREAS NORTH AND EAST WOULD BE COOLER/ BEGIN IN
THE WINTRY MIXTURE AREA...CROSS INTO FREEZING RAIN/RAIN...AND
FINALLY INTO RAIN BY THURSDAY MORNING. WBZS ARE USED TO DELINEATE
BETWEEN FREEZING RAIN OR RAIN AND THESE ARE BELOW FREEZING FOR THE
MOST PART OVERNIGHT...HENCE THE NEED FOR A WINTER WEATHER ADVISORY.
AGAIN...ACCUMULATIONS ARE EXPECTED TO REMAIN ONLY AT NUISANCE
LEVELS...BELOW 1/4 INCH.

OF THE GFS AND THE NAM...THE GFS IS THE MORE PREFERRED TRACK OF THE
SURFACE LOW AS IT MOVES NORTHEAST /NAM HAS A LOT OF CONVECTIVE
PRECIP ALONG THE COAST THAT HAS YET TO MATERIALIZE/...BUT HAVE STILL
OPTED TO SLOW IT DOWN SOMEWHAT AND ADJUST THE CIRCULATION CENTER
FURTHER TO THE SOUTHEAST TOWARDS THE BAROCLINICITY OF THE COASTAL
AREAS /A MORE TYPICALLY PREFERRED TRACK OF COASTAL LOWS/. EROSION
SEEMS TO BE TOO FAST...SO HAVE KEPT POPS IN FOR MOST OF THE DAY
THURSDAY. HOWEVER... MOSTLY CLEAR FOR FRIDAY. TEMPERATURES THURSDAY
WILL BE TOTALLY DEPENDENT UPON HOW QUICKLY THE PARENT HIGH MOVES OFF
THE EAST COAST...HOW QUICKLY THEN THE CAD WEDGE ERODES...AND IF
THERE IS ANY WRAPAROUND PRECIPITATION. FOR NOW...UPPER 30S
NORTHEAST...AND POTENTIAL FOR NEAR 60 SOUTHERN ZONES. NEAR FREEZING
THURSDAY NIGHT. 40S AND 50S FOR FRIDAY...AND COOLING AGAIN FRIDAY
NIGHT WITH 20S AND 30S.

THANKS MRX/GSP/CAE/CHS FOR COLLABORATION WITH THIS EVENT.

LONG TERM...(SATURDAY THROUGH WEDNESDAY)
HIGH PRESSURE BUILDS IN FROM THE WEST WHILE ANOTHER COASTAL LOW
DEVELOPS ALONG THE GULF COAST. IT SPREADS PRECIPITATION ACROSS THE
AREA MAINLY ON SUNDAY...PARTS OF NORTH GEORGIA MAY SEE SOME SNOW
EARLY THAT MORNING. FAIRLY SIGNIFICANT TROUGH DEVELOPS OVER THE EAST
COAST TUESDAY INTO WEDNESDAY...WHILE YET MORE MOISTURE IS PULLED
INTO THE AREA FROM ANOTHER GULF COAST SYSTEM. STRONG NORTHWEST FLOW
BEHIND THIS MAY ALLOW TEMPERATURES TO COOL ENOUGH TO BRING SNOW
AGAIN TO NORTHERN GEORGIA...BUT FOR NOW ONLY RAIN IN THE FORECAST
TUESDAY NIGHT INTO WEDNESDAY. HIGHS 40S AND 50S...LOWS 20S AND 30S.

AVIATION...
MVFR CEILINGS ALREADY DEVELOPING ACROSS NORTH GEORGIA AND THIS TREND
SHOULD CONTINUE. I EXPECT MVFR CEILINGS...MAINLY BETWEEN 2-3KFT...
FROM AHN WESTWARD ACROSS THE ATLANTA AREA TAF SITES BY 00Z. MCN AND
CSG WILL BE A LITTLE SLOWER...BUT SHOULD SEE CEILINGS DROP INTO THE
MVFR RANGE BETWEEN 00Z AND 03Z. ALL SITES WILL SEE VFR CEILINGS
DEVELOPING BETWEEN 06Z AND 09Z...PERSISTING THROUGH 18Z THURSDAY.
VISIBILITIES WILL ALSO DROP AFTER 03Z AS OCCASIONAL RAIN...MIXED
WITH SLEET AT TIMES...MOVES INTO THE REGION. VISIBILITIES SHOULD
DROP BELOW 3 MILES AFTER 06Z MOST AREAS AND REMAIN IN THE 1-3 MILE
RANGE UNTIL AROUND 18Z THURSDAY. PRECIPITATION SHOULD REMAIN MOSTLY
LIQUID AT ATL...FTY...PDK...RYY WITH A CHANCE FOR SLEET MIXED IN
THROUGH 06Z AS TEMPERATURES REMAIN AT OR ABOVE FREEZING OVERNIGHT.
AT AHN RAIN MIXED WITH SLEET WILL LIKELY SWITCH TO A MIXTURE OF RAIN
AND FREEZING RAIN AFTER 03Z...CONTINUING THROUGH 14Z TO 18Z
THURSDAY. FURTHER SOUTH...CSG AND MCN SHOULD SEE ALL LIQUID
PRECIPITATION WITH ONLY A SMALL CHANCE OF A LITTLE SLEET MIXED IN
THIS EVENING...MAINLY BETWEEN 00Z AND 04Z. WINDS WILL REMAIN EAST TO
SOUTHEAST THROUGH 15Z THURSDAY...THEN SHIFT TO THE SOUTHWEST AND
EVENTUALLY WEST THROUGH 00Z.

.PRELIMINARY POINT TEMPS/POPS...
ATLANTA         33  46  31  49 / 100 100   5   5
ATHENS          31  42  32  52 / 100 100   5  10
GAINESVILLE     31  38  30  50 / 100 100   5   5
ROME            38  50  28  50 / 100  90  10  10
COLUMBUS        42  57  34  53 /  90  90   5   5
MACON           38  55  31  56 /  90  90   5   5

&&

&&

.FFC WATCHES/WARNINGS/ADVISORIES...
ICE STORM WARNING UNTIL 1 PM THURSDAY FOR EXTEME NORTHEAST GEORGIA
WINTER WEATHER ADVISORY UNTIL 10 AM THURSDAY FOR PORTIONS OF NORTH
AND NORTHEAST GEORGIA.

&&

26

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE PEACHTREE CITY GA
912 PM EST WED DEC 14 2005

GAZ001>009-011>016-019>025-027-030>039-041>062-066>076-078>086-
089>098-102>113-160215-
DADE-WALKER-CATOOSA-WHITFIELD-MURRAY-FANNIN-GILMER-UNION-TOWNS-
CHATTOOGA-GORDON-PICKENS-DAWSON-LUMPKIN-WHITE-FLOYD-BARTOW-
CHEROKEE-FORSYTH-HALL-BANKS-JACKSON-MADISON-POLK-PAULDING-COBB-
NORTH FULTON-GWINNETT-BARROW-CLARKE-OCONEE-OGLETHORPE-WILKES-
HARALSON-CARROLL-DOUGLAS-SOUTH FULTON-DEKALB-ROCKDALE-WALTON-
NEWTON-MORGAN-GREENE-TALIAFERRO-HEARD-COWETA-FAYETTE-CLAYTON-
SPALDING-HENRY-BUTTS-JASPER-PUTNAM-HANCOCK-WARREN-TROUP-
MERIWETHER-PIKE-UPSON-LAMAR-MONROE-JONES-BALDWIN-WASHINGTON-
GLASCOCK-JEFFERSON-HARRIS-TALBOT-TAYLOR-CRAWFORD-BIBB-TWIGGS-
WILKINSON-JOHNSON-EMANUEL-MUSCOGEE-CHATTAHOOCHEE-MARION-SCHLEY-
MACON-PEACH-HOUSTON-BLECKLEY-LAURENS-TREUTLEN-STEWART-WEBSTER-
SUMTER-DOOLY-CRISP-PULASKI-WILCOX-DODGE-TELFAIR-WHEELER-
MONTGOMERY-TOOMBS-
912 PM EST WED DEC 14 2005

THIS HAZARDOUS WEATHER OUTLOOK IS FOR NORTH AND CENTRAL GEORGIA.

.DAY ONE...TONIGHT.

.SYNOPSIS...
SHALLOW...COLD...DRY AIR REMAINS IN PLACE OVER PORTIONS OF NORTH
GEORGIA THIS EVENING. WARMER AND VERY MOIST AIR WILL SWEEP ACROSS
NORTH AND CENTRAL GEORGIA ABOVE THIS COLD AIRMASS AT THE SURFACE
AS A LARGE STORM SYSTEM ALONG THE GULF COAST MOVES NORTHEAST
TOWARD GEORGIA.

PRIMARY HAZARDS...
THE MOST LIKELY TYPE OF PRECIPITATION WILL BE RAIN BUT SOME SLEET OR
SNOW FLURRIES WILL MIX IN THIS EVENING...WITH AREAS OF FREEZING
RAIN LIKELY IN NORTHEAST GEORGIA OVERNIGHT. AREAS LIKELY TO
EXPERIENCE A MIX OF WINTER PRECIPITATION WILL BE FROM THE
METROPOLITAN ATLANTA AREA NORTH AND EASTWARD THROUGH THURSDAY
MORNING.

DISCUSSION...
A DEVELOPING STORM SYSTEM ALONG THE GULF COAST WILL MOVE NORTHEAST
INTO CENTRAL GEORGIA OVERNIGHT. AS THIS SYSTEM APPROACHES...WARM
MOIST AIR WILL BE LIFTED ABOVE THE COOLER AIR AT THE SURFACE
ALLOWING PRECIPITATION TO FALL INTO THE COLDER AIR. WITH
TEMPERATURES IN THE LOW TO MID 30S ACROSS MUCH OF NORTH GEORGIA...
SOME OF THE RAIN THAT FALLS MAY BE ABLE TO FREEZE ON ELEVATED
SURFACES. ICY PATCHES WILL LIKELY BEGIN APPEARING BY LATE THIS
EVENING ACROSS NORTHEAST GEORGIA...ESPECIALLY ON BRIDGES AND
OVERPASSES.

.DAYS TWO THROUGH SEVEN...THURSDAY THROUGH TUESDAY.
SOME MIXED RAIN AND SLEET IS POSSIBLE ACROSS NORTH GEORGIA EARLY
SUNDAY MORNING...OTHERWISE NO HAZARDOUS WEATHER IS EXPECTED.

.SPOTTER INFORMATION STATEMENT...
SPOTTER ACTIVATION WILL NOT BE NEEDED THROUGH TONIGHT.

&&
FOR THE GRAPHICAL HAZARDOUS WEATHER OUTLOOK AND OTHER WEATHER
INFORMATION...PLEASE VISIT OUR WEBSITE AT WEATHER.GOV...AND CLICK ON
GEORGIA.