FXUS62 KGSP 101452
AFDGSP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
952 AM EST THU DEC 10 2009
.SYNOPSIS...
STRONG HIGH PRESSURE WILL BUILD ACROSS THE FORECAST AREA TODAY WHILE
A COLD FRONT CONTINUES TO WEAKEN OFF THE EAST COAST. MOISTURE WILL
INCREASE FROM THE SOUTH THROUGH SATURDAY AS AN AREA OF LOW PRESSURE
MOVES EAST ALONG THE NORTHERN GULF COAST. THIS LOW WILL MOVE UP THE
CAROLINA COASTLINE THROUGH SUNDAY...BEFORE A WEAK AREA OF HIGH
PRESSURE BUILDS OVER THE AREA MONDAY.
&&
.NEAR TERM /THROUGH TONIGHT/...
A BROAD UPPER TROUGH REMAINS OVER MUCH OF NORTH AMERICA THIS
MORNING...WITH ITS AXIS JUST WEST OF THE MS RIVER...AND FAST MID
LEVEL FLOW FROM THE CENTRAL ROCKIES TO THE MID ATLANTIC STATES. A
COLD FRONT WAS ANALYZED OFF THE CAROLINA COAST THIS MORNING...WITH A
TIGHT PRESSURE GRADIENT IN ITS WAKE OVER THE SOUTHERN APPALACHIANS
AND HIGH PRESSURE OVER THE SOUTHERN PLAINS. SOME LOW CLOUDS WERE
LOCATED OVER THE NORTHERN NC MOUNTAINS...BUT TO THE EAST FEW
CLOUDS REMAINED OVER OUR AREA.
CLOUD COVER WILL BE LOWERED IN THE FOOTHILLS AND PIEDMONT PER
SATELLITE IMAGERY. WINDS ARE EXPECTED TO STAY UP OVER THE NC
MOUNTAINS...AND THE WIND ADVISORY FOR THE NORTHERN MOUNTAINS...AND
LAKE WIND ADVISORY FOR THE CENTRAL MOUNTAINS WILL REMAIN IN EFFECT.
COLD ADVECTION WILL CONTINUE TODAY...PARTIALLY OFFSET BY DOWNSLOPE
FLOW IN THE LEE OF THE MOUNTAINS. MAXIMUMS TEMPERATURES WILL BE
RAISED A DEGREE OR TOW IN THE CENTRAL AND SOUTHERN NC MOUNTAINS...AS
THE KCLT AREA...AND LOWERED A DEGREE OR TWO IN THE INTERSTATE 40
CORRIDOR...PER CURRENT TRENDS AND THE LATEST GUIDANCE.
SAVE FOR THE HIGH ELEVATIONS...WHICH WILL REMAIN BLUSTERY...SFC
RIDGING WILL BUILD IN TONIGHT LOOSENING PRESSURE GRADIENT. WITH JUST
A FEW HIGH CLOUDS EXPECTED...WILL CONTINUE TO FAVOR THE COOLER MET
NUMBERS FOR FRIDAY MORNING MINS.
&&
.SHORT TERM /FRIDAY THROUGH SUNDAY/...
AS OF 215 AM THURSDAY...HIGH PRESSURE WILL REMAIN OVER THE REGION ON
FRIDAY. CONFLUENT UPPER TROPOSPHERIC FLOW AND A 180+ KT JET WILL
PROVIDE PLENTY OF SUPPORT FOR THE RIDGE. THICKNESSES WILL BE QUITE
LOW...AND MAX TEMPS WON/T CLIMB OUT OF THE L-M40S OVER THE FOOTHILLS
AND PIEDMONT AND THE 30S IN THE MTNS. HIGH CLOUDS WILL BE ON THE
INCREASE...WHICH COULD KEEP MAXES EVEN A HAIR COOLER.
AS THE PREVIOUS SHIFT NOTED...WE ARE DEALING WITH LOW AMPLITUDE SRN
STREAM SHORT WAVES WITH THIS NEXT PCPN EVENT...A TYPICAL BANE OF AN
EL NINO WINTER. WHEN THE FORCING IS THIS WEAK...IT/S HARD TO KNOW
JUST WHEN THE LLVL WARM ADVECTION WILL BECOME STRONG ENOUGH TO
SUPPORT PCPN. ALSO...WITH SUCH A DRY RIDGE OF ARCTIC ORIGINS OVER
THE REGION...THE WESTERN CAROLINAS WILL BE ONE OF THE LAST PLACES TO
SEE PCPN OWING TO THE DEEP MASS OF COOL...DRY AIR. I/VE PUSHED
TIMING BACK AGAIN...AND NOW DON/T HAVE PCPN STARTING OVER THE REGION
UNTIL SAT AFTN. EVEN THIS COULD BE OVERDONE AS THE STRONGEST FORCING
ON THE LATEST MODEL RUNS LOOKS TO REMAIN OVER THE MIDLANDS AND LOW
COUNTRY.
THERE WILL BE ENOUGH OF A WARM NOSE...THAT ONLY A BRIEF PERIOD OF
SNOW IS POSSIBLE ON SAT...MAINLY OVER THE MTNS. SOME SLEET IS
PROBABLE OVER WRN NC SAT AFTN AND EVENING...AND MAYBE A LITTLE
FREEZING RAIN OVER THE MTNS SAT NIGHT AND SUNDAY MORNING AS THE CAD
REGION MOISTENS. I/VE CUT WAY BACK ON QPF...AND UNLESS THE MODELS
SHIFT THE PCPN CONSIDERABLY FARTHER NORTH...WE ARE NOT LOOKING AT
MUCH OF A WINTER PCPN EVENT OVER THE NC FOOTHILLS AND PIEDMONT.
PERHAPS THERE WILL BE ENOUGH PCPN FOR A WINTER WEATHER
ADVISORY...BUT THAT/S NOT LOOKING VERY LIKELY.
TEMPS WILL WARM ENOUGH ON SUNDAY FOR ANY FZRA OR SLEET OVER THE NC
ZONES TO CHANGE TO RAIN. THE MODELS PUSH A WEAK LOW UP THE COAST
DURING THE DAY AS THE LAST IN A SERIES OF ILL-DEFINED SRN STREAM
SHORT WAVES MOVES EAST OF THE REGION...FOLLOWED BY A BRIEF PERIOD OF
SHORT WAVE RIDGING.
&&
.LONG TERM /SUNDAY NIGHT THROUGH WEDNESDAY/...
AS OF 200 AM THURSDAY...THERE IS LITTLE NEED TO ADJUST THE GOING
FORECAST BASED OF THE LATEST OBJECTIVE GUIDANCE. THE OP MODELS
AGREE PRETTY WELL WITH DEVELOPING A DEEP E COAST TROF BY MID NEXT
WEEK...WITH VARYING DIFFERENCES AS HOW MUCH SPLIT FLOW WILL
DEVELOPED. THE ECMWF IS MORE SPLIT WITH THE UPPER JET PATTERN AND
THEREFORE MORE ZONAL AND WARMER THAN THE GFS. THUS...THE ECMWF LOOKS
SLOW IN BRINGING THE ARCTIC AIRMASS INTO THE UPPER MIDWEST...WHEN
COMPARED TO THE MORE PROGRESSIVE GFS.
IN ANY REGARD...THE LLVL SYNOPTIC PATTERN IS RELATIVELY CLOSE WRT
THE FAST MOVING CLIPPER CROSSING THE OH VALLEY AND INTO S QUEBEC BY
MON NIGHT. THE MAIN ACTION FOR THE CWFA WILL BE THE AMOUNT GOM
MOISTURE FLUX REACHING THE AREA BEFORE A RATHER STRONG ARCTIC HIGH
BUILDS IN FROM THE NW. STILL EXPECT A S/W RIDGE TO CROSS THE REGION
MON KEEPING THINGS DRY...AND WITH DECENT S/LY FLOW THROUGHOUT THE
DAY MAX TEMPS SHOULD HAVE NO PROBLEM MODIFYING ABOUT 10 DEGREES
WARMER THAN SUN.
ITS INTERESTING THAT BOTH MODELS SHOW COMPARABLE PLACEMENT AND
STRENGTH OF THE SOUTHERN STREAM CONVECTION...EVEN THO THE ULVL
PATTERNS ARE SO DIFFERENT BETWEEN THEM. WITH THE GEFS ENS MEMBERS
HAVING MUCH LESS SPREAD IN THE SOUTHERN STREAM COMPONENT THAN THE
NORTHERN S/W TROF...THERE IS REASONABLE CONFIDENCE THAT THE ECMWF/S
SPLIT FLOW SOLN IS PROBABLY SUPPORTED BY THE GFS MORESO THAN THE OP
MODELS MAY INDICATE....ESP GIVEN THE RECENT DEC PATTERN.
SO...SUFFICE TO SAY THE TIMING OF GOM MOISTURE WILL BE WEIGHTED
MORESO WITH THE MOISTURE FLUX OF THE ECMWF. THIS AGREES WELL WITH
CONTINUING THE HIGH CHANCE POPS FOR TUE AND HPC 18Z GUIDE. THE LLVL
THERMAL FIELDS ARE ON TRACK WITH THE PREVIOUS FORECAST AS WELL...SO
ISOL WRAP AROUND NC MTN SN SHOWERS STILL LOOK GOOD TUE NIGHT WITH
LLVL MOISTURE WANING QUICKLY BY 12Z WED.
&&
.AVIATION /15Z THURSDAY THROUGH MONDAY/...
AT KCLT...WNW WINDS SHOULD CONTINUE ALL DAY AND BECOME GUSTY
BY/AROUND MIDDAY...THEN LOOSING GUSTINESS BY THIS EVENING AND
VEERING TO NW AND LIGHTENING THRU THE NIGHT.
ELSEWHERE ACRS THE FA...GUSTY NW WINDS TO REMAIN AT KAVL INTO THIS
EVENING. ACRS THE FTHLS TAFS...GUSTY WESTERLY WINDS TO REDEVELOP
LATER THIS MORNING AND THEN DIMINISH WITH LOSS OF HTG THIS EVENING.
OUTLOOK...VFR EXPECTED FRIDAY. A GULF COAST STORM SYSTEM COULD
SPREAD LIGHT MIXED PRECIP INTO THE REGION SATURDAY AFTERNOON INTO
THE NIGHT. FLIGHT RESTRICTIONS COULD LINGER INTO SUNDAY.
&&
.FIRE WEATHER...
MIXING HEIGHTS WILL BE RAISED 300 TO 400 FEET TODAY...PER THE LATEST
MODEL SOUNDINGS AND TEMPERATURE FORECAST. RELATIVE HUMIDITY WILL BE
QUITE LOW...AND WINDS QUITE GUSTY...HOWEVER FUEL MOISTURE SHOULD
REMAIN HIGH DUE TO HEAVY RAINFALL YESTERDAY.
&&
.GSP WATCHES/WARNINGS/ADVISORIES...
GA...NONE.
NC...WIND ADVISORY UNTIL 6 PM EST THIS EVENING FOR NCZ033-049-050-
501-503-505.
LAKE WIND ADVISORY UNTIL 6 PM EST THIS EVENING FOR NCZ048-052-
053-064-065-507-509.
SC...NONE.
&&
$$
SYNOPSIS...SBK
NEAR TERM...CSH/JAT
SHORT TERM...MCAVOY
LONG TERM...SBK
AVIATION...CSH
FIRE WEATHER...JAT
