FXUS62 KGSP 271146
AFDGSP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
646 AM EST FRI NOV 27 2009
.SYNOPSIS...
HIGH PRESSURE WILL BUILD OVER THE REGION TODAY AND REMAIN IN CONTROL
THROUGH THE WEEKEND. A COLD FRONT WILL THEN MOVE OVER THE CAROLINAS
ON MONDAY AND MONDAY NIGHT. ANOTHER LOW PRESSURE SYSTEM WILL MAKE
ITS WAY OUT OF THE GULF OF MEXICO AND MOVE OVER THE AREA BY MID WEEK.
&&
.NEAR TERM /THROUGH TONIGHT/...
MID LEVEL HEIGHTS WILL CONTINUE TO INCREASE ACROSS THE NC MTNS EARLY
THIS MORNING THROUGH MID DAY. AS HEIGHTS INCREASE...LLVL FLOW WILL
BACK AND MOISTURE WILL BECOME INCREASINGLY LIMITED. AT
8Z...RECENT IR SATELLITE IMAGES INDICATED A WARMING TREND WITH MOST
CLOUD TOP TEMPS IN THE -10 TO -13C RANGE. IN ADDITION...LATEST RADAR
IMAGES INDICATED LITTLE TO NO REFLECTIVITY. IT APPEARS THAT LIGHT
ADDITIONAL SNOWFALL IS POSSIBLE THIS MORNING...BUT LESS THAN A HALF
INCH. I WILL KEEP THE WINTER WEATHER ADVISORY IN PLACE UNTIL NOON.
FORECAST SOUNDINGS AND MODEL PRESSURE FIELDS INDICATE THAT WIND
GUSTS WILL LIKELY STRENGTHEN ACROSS THE HIGH TERRAIN TODAY. DAYTIME
MIXING HEIGHTS MAY REACH H85...POSSIBLY RESULTING GUSTS AROUND 40
KTS ACROSS THE MTNS AND 30 KTS ACROSS THE ADJACENT FOOTHILLS. GUSTY
CONDITIONS WILL LIKELY PERSIST ACROSS THE NRN MTNS INTO THE LATE
NIGHT. I WILL KEEP THE CURRENT WIND ADVISORY IN PLACE...BUT WILL
EXTEND THE NRN MTN ADVISORY UNTIL 6 AM FRIDAY.
LLVL THICKNESSES WILL REMAIN QUITE COOL ACROSS THE FORECAST AREA
TODAY. CLOUD COVER WILL LIKELY RANGE FROM CLOUDY TO MOSTLY CLOUDY
ACROSS THE WESTERN SLOPES OF THE MTNS...TO SUNNY TO MOSTLY SUNNY
EAST. DOWNSLOPE FLOW AND STRONG INSOLATION SHOULD ALLOW TEMPERATURES
TO PEAK WITHIN 5-7 DEGREES OF NORMAL EAST OF THE MTNS.
HOWEVER...THICK CLOUD COVER...CAA...AND AREAS OF LIGHT SNOWCOVER
SHOULD KEEP TEMPERATURES LIMITED TO THE MID TO U30S ACROSS THE TN
BORDER AND 40S ACROSS THE REMAINDER OF THE MTNS. TONIGHT...WEAKENING
WINDS AND DECREASING CLOUD COVER WILL ALLOW TEMPERATURES TO FALL
STEADILY AFTER SUNSET. MOS GUIDANCE SUPPORTS WIDESPREAD FREEZING
TEMPERATURES...RANGING FROM THE MID TO U20S ACROSS THE MTNS AND L30S
EAST.
&&
.SHORT TERM /SATURDAY THROUGH MONDAY NIGHT/...
AS OF 130 AM FRIDAY...STILL LOOKS LIKE A PERIOD OF QUIET WEATHER
SATURDAY AND SATURDAY NIGHT AS AN UPPER RIDGE AND SURFACE HIGH
PRESSURE BUILD OVER THE SOUTHEAST. KEPT TEMPS CLOSE TO A GUIDANCE
BLEND. THE PATTERN REMAINS PROGRESSIVE THOUGH...SO THIS WILL BE
SHORT LIVED. A WEAK UPPER WAVE WILL FLATTEN THE RIDGE ON SUNDAY AND
COULD BRING SOME MID/HIGH LEVEL CLOUDS...BUT NOT ENOUGH TO KEEP
TEMPS FROM WARMING WELL INTO THE 60S IN THE AFTERNOON.
THE GFS AND ECMWF ARE IN FAIRLY GOOD AGREEMENT WITH DIGGING AN UPPER
TROF DOWN ACROSS THE PLAINS SUNDAY NIGHT. MOISTURE WILL RETURN FROM
THE GULF AHEAD OF A COLD FRONT ASSOCIATED WITH THIS UPPER TROF.
THERE IS THE POSSIBILITY THAT SOME SHOWER ACTIVITY WILL REACH THE
MOUNTAINS BEFORE SUNRISE ON MONDAY BUT THAT SEEMS REMOTE. INSTEAD...
MOST OF THE SHOWER ACTIVITY WILL DEVELOP ACROSS THE FORECAST AREA ON
MONDAY AS THE FRONT APPROACHES FROM THE WEST AND THE SRN BRANCH OF
THE JET MOVES OVERHEAD. THIS SHOULD GIVE US A DECENT SHOT AT SEEING
SHOWERS...SO WENT WITH THE LIKELY ON THE TN BORDER AND CHANCE
ELSEWHERE. THE FRONT SHOULD PUSH ACROSS THE REGION MONDAY EVENING
BUT KEPT CHANCE POP ALL NIGHT IN CASE TIMING SLIPS.
&&
.LONG TERM /TUESDAY THROUGH THURSDAY/...
AS OF 2 AM FRIDAY...THE MEDIUM RANGE FORECAST PICKS UP AT 12Z ON
TUESDAY WITH SFC HIGH PRESSURE BRIEFLY IN CONTROL OVER THE CWFA AND
PREDOMINATELY DRY AIR OVER THE REGION. AS THE UPPER LOW DEEPENS OVER
THE SW CONUS THE ASSOCIATED SFC CYCLONE STRENGTHENS OVER THE
NORTHERN GULF OF MEX. LATEST 00Z GFS CONTINUES TO TRACK THE SFC LOW
RIGHT OVER THE CAROLINAS AND IS ABOUT 12 HOURS FASTER THAN THE ECMWF
AND GEM. THE LOW MOVES RAPIDLY UP THE EASTERN SEABOARD TOWARDS THE
END OF THE PERIOD AS A ANOTHER SFC RIDGE PUSHES ITS WAY IN FROM THE
NW. FOR THE MOST PART THE MODELS REMAIN IN GOOD AGREEMENT EXCEPT FOR
THE OVERALL FASTER PROGRESSION OF THE GFS AND ITS TENDENCY TO PUSH
THE LOW ON MORE OF AN EASTERLY TRACK. MODEL SOUNDINGS SHOW LITTLE
EVIDENCE THAT ANY FROZEN PRECIP SHOULD BE EXPECTED SO I KEPT ALL QPF
AS LIQUID. TEMPS SHOULD MODERATE BY THURSDAY AND INCREASE TO NEAR
NORMAL WITH THE FLOW TURNING FROM THE S AND SW DURING THE DAY.
&&
.AVIATION /12Z FRIDAY THROUGH TUESDAY/...
AT KCLT...UNLIMITED VISIBILITY AND CLEAR SKY COVER WILL REMAIN
THROUGH THE TAF PERIOD. SFC RIDGE ACROSS THE LOWER MISSISSIPPI RIVER
VALLEY COMBINED WITH LOW PRESSURE OFF THE COAST OF NEW ENGLAND WILL
RESULT IN SIGNIFICANT PRESSURE GRADIENT ACROSS THE NC PIEDMONT
TODAY. FORECAST SOUNDINGS INDICATE THAT THE MIXING LAYER WILL
INCREASE STEADILY AFTER SUNRISE. BY 15Z...THE DEPTH OF THE MIXING
LAYER WILL RESULT IN ENOUGH MOMENTUM TRANSFER TO YIELD GUSTS IN THE
15-20 KT RANGE. IN ADDITION...A SHARP LEE TROF ACROSS THE FOOTHILLS
WILL LIKELY RESULT IN PERIODS OF CHAOTIC WINDS TODAY. BASED ON THE
ORIENTATION OF THE PRESSURE FIELDS...I WILL FORECAST A WEST-SOUTHWEST
WIND...FAVORING 250 DEGREES...FOR MOST OF THE DAYTIME. AROUND
SUNSET...22Z...WINDS WILL DECOUPLE RAPIDLY TO AROUND 5 KTS FROM THE
WEST.
ELSEWHERE...VFR CONDITIONS WILL CONTINUE THROUGH THE TAF PERIOD.
WEST WINDS WILL GRADUALLY STRENGTHEN AFTER SUNRISE. INCREASED MIXING
WILL RESULT IN GUSTS TO 15 TO 25 KTS BY MID MORNING AND WILL REMAIN
UNTIL SUNSET. KAVL WILL SEE NORTHWEST WINDS WITH GUSTS NEAR 30 KTS.
AFTER SUNSET...WINDS WILL DECOUPLE RAPIDLY TO AROUND 5 KTS FROM THE
WEST-NORTHWEST.
OUTLOOK...DRY HIGH PRESSURE WILL DOMINATE THE AREA ON SATURDAY AND
WILL GRADUALLY WEAKEN ON SUNDAY. LIGHT WINDS AND CLEAR CONDITIONS
WILL PERSIST THROUGH THE WEEKEND. A COLD FRONT IS EXPECTED TO REACH
THE WESTERN CAROLINAS LATE SUNDAY NIGHT AND SWEEP ACROSS THE REGION
ON MONDAY.
&&
.GSP WATCHES/WARNINGS/ADVISORIES...
GA...WIND ADVISORY UNTIL 6 PM EST THIS EVENING FOR GAZ010.
NC...WINTER WEATHER ADVISORY UNTIL NOON EST TODAY FOR NCZ033-
048>053-058-059-501-503-505.
WIND ADVISORY UNTIL 6 AM EST SATURDAY FOR NCZ033-049-050-501-
503-505.
WIND ADVISORY UNTIL 6 PM EST THIS EVENING FOR NCZ048-051>053-
058-059-062>065-507-509.
SC...NONE.
&&
$$
SYNOPSIS...JPT
NEAR TERM...NED
SHORT TERM...PM
LONG TERM...JPT
AVIATION...NED
