000
FXUS62 KGSP 280831
AFDGSP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
331 AM EST TUE DEC 28 2010
.SYNOPSIS...
HIGH PRESSURE WILL CONTINUE ACROSS THE SOUTHEASTERN STATES THROUGH
WEDNESDAY...BEFORE A WEAK FRONTAL SYSTEM AFFECTS THE WESTERN
CAROLINAS AND NORTHEAST GEORGIA ON THURSDAY. HIGH PRESSURE WILL
REMAIN OFF THE CAROLINA COAST THROUGH SATURDAY AS A COLD FRONT
APPROACHES THE AREA FROM THE WEST.
&&
.NEAR TERM /THROUGH TONIGHT/...
BROAD HIGH PRESSURE WILL BUILD ACROSS THE DEEP SOUTH WITH WEAK
RIDGING ACROSS THE SOUTHERN APPALACHIANS THIS AFTERNOON. EAST OF THE
MTNS...A SHALLOW LEE TROF WILL DEVELOP THIS MORNING AND REMAIN
THROUGH THE AFTERNOON. WINDS WILL REMAIN VERY LIGHT TODAY...FAVORING
A SW DIRECTION. SATELLITE TRENDS AND FORECAST SOUNDINGS INDICATE
SUNNY CONDITIONS TODAY. GOOD INSOLATION AND WEAK RETURN FLOW WILL
RESULT IN TEMPS IN THE 30S ACROSS THE MTNS AND L40S EAST. THE
SNOWPACK SHOULD SEE SIGNIFICANT MELTING TODAY...ESPECIALLY EAST OF
THE MTNS. I WILL KEEP HIGH LIMITED BELOW MOS ACROSS THE SNOW COVERED
AREAS.
TONIGHT...MID LEVEL TROF WILL DIG WITHIN THE LEE OF THE ROCKIES WITH
SHALLOW RIDGING OVER THE EASTERN STATES. CONDITIONS SHOULD REMAIN
CLEAR TO MOSTLY CLEAR THIS EVENING...THEN HIGH CLOUDS WILL INCREASE
FROM THE WEST BY LATE TONIGHT. STEADY LLVL WWA AND INCREASING SKY
COVER WILL PROVIDE SOME LIMITATION TO COOLING TONIGHT. I WILL USE A
BLEND OF MOS FOR MINS...GIVING THE MTNS TEENS IN THE VALLEYS TO NEAR
20 ACROSS THE RIDGES AND EAST OF THE MTNS. TEMPERATURES WELL BELOW
FREEZING WILL REFREEZE MELT WATER AND SLUSH AGAIN TONIGHT.
OTHERWISE...CONDITIONS WILL BE JUST COLD AND CALM.
&&
.SHORT TERM /WEDNESDAY THROUGH FRIDAY/...
AS OF 310 AM TUE...WEDNESDAY WILL BE A NICE DAY...ALBEIT WITH
INCREASING HIGH CLOUDS. MODEL THICKNESSES SUPPORT HIGHS FROM THE MID
40S MTNS TO L50S PIEDMONT WITH FULL SUN. I UNDERCUT THAT BY A COUPLE
DEGREES ON ACCOUNT OF THE CLOUD COVER.
ON THURSDAY A SHORT WAVE TROUGH WILL APPROACH THE REGION FROM THE
SOUTHWEST. THE TROUGH WILL QUICKLY DAMPEN OUT AS IT MOVES INTO AN
AREA OF RISING HEIGHTS ACROSS THE ERN CONUS. EVEN THOUGH THE SHORT
WAVE WEAKENS AS IT MOVES INTO THE WRN CAROLINAS...THE DEEP LAYER
RH/S ARE STILL FAIRLY HIGH ACROSS THE MTNS THU MORNING ON THE GFS
AND THE 00 UTC ECMWF. THE NAM LOOKS TOO AGGRESSIVE WITH MOISTURE ON
THU MORNING. THE MOISTURE IS SUPPORTED THROUGH A COMBINATION OF
WEAK LLVL WARM ADVECTION AND MOISTURE THAT/S INTRODUCED INTO THE
UPSTREAM FLOW FROM CONVECTION THAT DEVELOPS ALONG THE GULF COAST
WITH THE EJECTING SHORT WAVE. I DON/T THINK ANY LIGHT PCPN WILL HAVE
MUCH LUCK MAKING IT EAST OF THE MTNS ON THU AS STRONG SUBSIDENCE
UNDER THE MID-TROPOSPHERIC RIDGE WILL KEEP THE AIRMASS DRY. WEAK
COLD AIR DAMMING WILL ALSO HELP TO THE THE LLVLS OF THE AIRMASS DRY
OVER THE FOOTHILLS AND PIEDMONT.
THEREFORE...THE SLIGHT CHANCE POPS OVER THE MTN ZONES EARLY THU
STILL LOOK ON TRACK. I STILL HAVE SOME FREEZING RAIN IN THE GRIDS
THU MORNING...MAINLY IN THE NC MTN VALLEYS. THIS TYPE OF EVENT CAN
STILL CAUSE PROBLEMS IN THE MTNS AS IT ONLY TAKES A TRACE OF PCPN TO
CAUSE SIGNIFICANT TRAVEL PROBLEMS WITH FREEZING RAIN. IT/S CERTAINLY
POSSIBLE THAT A FREEZING RAIN ADVISORY MAY BEEN NEEDED EARLY
THU...EVEN THOUGH THE QPF WILL BE ONLY A COUPLE HUNDREDTHS OF AN
INCH.
THE SHORT WAVE WILL BE OUT OF THE PICTURE BY THU NIGHT...BUT THE
LLVL WARM ADVECTION AND CLOUD COVER WILL STILL REMAIN. IN FACT...THE
GFS DEVELOPS A CONSIDERABLE AMOUNT OF LLVL CLOUD COVER ON FRIDAY AS
LIFT STRENGTHENS OVER THE WEAK COLD AIR DAMMING. THE NAM ONLY GOES
THROUGH 12 UTC FRI...BUT IT/S SLOWER WITH THE MOISTURE RETURN THAN
THE GFS. I STILL HAVE MOSTLY CLOUDY SKIES OVER MOST OF THE FA ON
FRI...BUT WITH ANY LUCK THIS MAY TURN OUT TO BE A PESSIMISTIC
FORECAST.
&&
.LONG TERM /FRIDAY NIGHT THROUGH MONDAY/...
AS OF 230 AM TUESDAY...OPERATIONAL MODELS CONTINUE TO EXHIBIT
EXCELLENT AGREEMENT IN THE MEDIUM RANGE AND AS SUCH NO SIGNIFICANT
CHANGES HAVE BEEN MADE TO THE FORECAST. THE HIGH AMPLITUDE MID AND
UPPER LEVEL RIDGE WILL SHIFT OFF THE EAST COAST ON SATURDAY AS AN
UPPER LOW RIDES NORTHEASTWARD INTO THE GREAT LAKES REGION. A FRONTAL
BAND WILL APPROACH THE AREA FROM THE WEST DURING THE DAY ON
SATURDAY...THOUGH BOTH THE GFS AND ECMWF DEPICT DECENT PREFRONTAL
SHOWER ACTIVITY ACTIVATING IN WAA FLOW. OVERALL THE FRONT WILL TAKE
ITS TIME IN CROSSING THE AREA WITH FROPA NOT EXPECTED UNTIL SUNDAY
AFTERNOON. ALL IN ALL...IT LOOKS LIKE A FAIRLY VANILLA BOUNDARY WITH
ANY SURFACE BASED INSTABILITY LIMITED TO AREAS FAR TO THE SOUTH
ALONG THE GULF COAST. TEMPS WILL BE NICE AND MILD THROUGH
SUNDAY...COOLING ONLY TO AROUND CLIMO IN THE POST FRONTAL AIRMASS ON
MONDAY.
&&
.AVIATION /09Z TUESDAY THROUGH SATURDAY/...
AT KCLT AND ELSEWHERE...CLEAR SKY WITH UNLIMITED VISIBILITY THROUGH
THE TAF PERIOD. KAVL...GUSTY NORTHWEST WINDS SHOULD STEADILY WEAKEN
THROUGH THE REST OF THE NIGHT. BY 9Z...RELAXING PRESSURE GRADIENT
AND WEAKER LLVL FLOW SHOULD END SIGNIFICANT GUSTS...LEAVING A
NORTHWEST WINDS AROUND 7KTS THROUGH THE REST OF THE PERIOD. BROAD
LEE TROF SHOULD SUPPORT WEAK SOUTHWEST WINDS EAST OF THE MTNS AFTER
SUNRISE.
OUTLOOK...VFR ON WED. CHANCE OF PRECIP AND RESTRICTIONS THU-SAT. IF
PRECIP BEGINS EARLY THU MRNG THERE COULD BE A BRIEF PERIOD OF
FREEZING RAIN OVER MTN VALLEYS.
&&
.GSP WATCHES/WARNINGS/ADVISORIES...
GA...WINTER WEATHER ADVISORY UNTIL NOON EST TODAY FOR GAZ026-028-
029.
NC...WINTER WEATHER ADVISORY UNTIL NOON EST TODAY FOR NCZ033-
035>037-048>053-056>059-062>065-068>072-082-501>510.
SC...WINTER WEATHER ADVISORY UNTIL NOON EST TODAY FOR SCZ003-007-
008.
&&
$$
SYNOPSIS...BSH
NEAR TERM...NED
SHORT TERM...MCAVOY
LONG TERM...BSH
AVIATION...NED
