FXUS62 KGSP 061754
AFDGSP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
1254 PM EST SUN DEC 6 2009
.SYNOPSIS...
HIGH PRESSURE WILL CONTINUE OVER THE EASTERN SEABOARD THROUGH EARLY
MONDAY. A COLD FRONT WILL CROSS THE APPALACHIANS MONDAY NIGHT WITH
ANOTHER AREA OF HIGH PRESSURE MOVING IN BRIEFLY BEHIND IT. A STRONG
LOW WILL DEVELOP OVER THE ROCKIES EARLY IN THE WEEK AND REACH THE
OHIO RIVER VALLEY ON WEDNESDAY AS AN ASSOCIATED COLD FRONT
APPROACHES THE CAROLINAS AND GEORGIA FROM THE WEST.
&&
.NEAR TERM /THROUGH MONDAY/...
WEAK SHORTWAVES WILL CROSS THE FORECAST AREA IN WSW FLOW ALOFT
TONIGHT THROUGH MONDAY. HIGH LEVEL CLOUDINESS WILL BE FAIRLY
ABUNDANT THROUGH THE PERIOD WITH A STOUT JETLET OVERHEAD IN THE WSW
FLOW. A BAND OF LOW LEVEL MOISTURE IN THE 900 TO 850 MB LAYER WILL
MAKE A RUN AT THE SOUTHEAST PIEDMONT FROM A COASTAL ATLANTIC SOURCE
REGION OVERNIGHT. THESE CLOUDS MAY REACH THE INTERSTATE 77 CORRIDOR
AROUND DAYBREAK BEFORE PIVOTING AWAY TO THE NE THROUGH THE DAY. NO
PRECIPITATION IS INDICATED...WITH THE SFC LAYER REMAINING DRY.
OTHERWISE...ANY DEEPER MOISTURE LOOKS FAIRLY SPARSE THROUGH THE
PERIOD. SLIGHTLY BETTER RH SHOULD ARRIVE FROM THE W DURING THE AFTN
HOURS MONDAY...WITH SLIGHT CHANCE POPS FOR SHOWERS IN THE MTNS.
CHILLY MINS IN THE 20S AND LOW 30S ARE EXPECTED OVERNIGHT...WITH
COOL MAXES IN THE 40S TO LOW 50S ON MONDAY.
&&
.SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY/...
AS OF 200 AM SUNDAY...WEAKLY FORCED FRONTAL PASSAGE REMAINS SLATED
FOR MONDAY...WITH BEST SHOWER CHANCES...ALBEIT SLIGHT...REMAINING
LIMITED TO THE MTNS IN THE AFTERNOON WHERE THE NAM CROSSSECTIONS
DEPICT SOME DEEPENING OF 85H/70H RH. SREF POPS SUPPORT THE GOING
SLIGHT CHANCE OF AFTERNOON/EVENING MTN SHOWERS...OTHERWISE VARIABLY
CLOUDY WITH MAX TEMPS A FEW DEGREES BELOW CLIMO.
BOTH THE 00 UTC OP GFS/NAM ARE IN AGREEMENT IN SPREADING WAA PCPN
INTO THE WESTERN CWFA TUESDAY MORNING AND ACRS THE REST OF THE
REGION AS THE DAY WEARS ON...COINCIDENT WITH THE MAGNITUDE OF LLVL
WAA FLOW. EVEN AT PCPN ONSET...MODEL FCST SNDGS AND PARTIAL
THICKNESS VALUES CONTINUE TO INDICATE AN ALL LIQUID PCPN
EVENT...ALTHOUGH DEPENDING ON HOW COLD MINS WIND UP EARLY
TUESDAY...A LOW PROBABILITY FZRA PERIOD ACRS THE DEEPER NC MTN
VALLEYS DOES EXIST. BASED ON THE MODEL AGREEMENT...WILL
PROBABLY CONTINUE THE UPWARD TREND IN POPS.
THE POTENTIAL FOR EMBEDDED HEAVY PCPN ELEMENTS...ESPECIALLY ACRS
THE UPSLOPE AREAS...WILL ARISE TUESDAY NIGHT AS 50 KT 85H JET
TRANSLATES ACRS THE CWFA. LINGERING FRONTAL BAND SHOWERS WEDNESDAY
MORNING ARE PROGGED TO DIMINISH AS THE DAY WEARS WITH ENCROACHMENT
OF DRY SLOT THEN LATE DAY COLD FRONTAL PASSAGE.
&&
.LONG TERM /WEDNESDAY NIGHT THROUGH SATURDAY/...
AS OF 250 AM SUNDAY...STARTING AT 00Z THURSDAY...LESS AND LESS
MOISTURE IS SHOWN WITH EACH RUN WITH NORTHWEST FLOW OVER THE NC
MOUNTAINS AS THE DEPARTING LOW EXITS THE NORTHEAST. THEREFORE I
HAVE DECREASED THE POPS WEDNESDAY NIGHT AND TRENDED THE SMALLER POPS
WEIGHTED TOWARD THE NORTHERN MOUNTAINS. THE WIND WILL BE AT LEAST
LAKE WIND CRITERIA WEDNESDAY NIGHT INTO EARLY THURSDAY UNTIL THE
PRESSURE GRADIENT DIMINISHES WITH THE CENTER OF HIGH PRESSURE
APPROACHING ON THURSDAY. THIS HIGH WILL TRAVERSE THE AREA AND
MOVING OFF THE MID ATLANTIC FRIDAY NIGHT. AN AREA OF LOW PRESSURE
WILL MOVE EAST NORTHEAST ALONG THE NEARLY STALLED OUT FRONTAL
BOUNDARY TO OUR SOUTH LATE FRIDAY NIGHT AND SATURDAY. THIS WILL
MOVE OFF THE CAROLINA COAST SATURDAY NIGHT. TEMPERATURES WILL NOT
CHANGE MUCH FROM DAY TIME TO DAY TIME. NIGHT TIME TEMPERATURES WILL
BE LOWER UNDER THE CENTER OF HIGH PRESSURE FRIDAY MORNING AND AGAIN
AFTER THE WEEKEND SYSTEM...BUT MILDER UNDER THE INCREASED CLOUD
COVER.
&&
.AVIATION /18Z SUNDAY THROUGH FRIDAY/...
AT KCLT AND ELSEWHERE...HIGH CIRRUS CEILINGS WILL PERSIST THROUGH
THE PERIOD AT ALL TAF LOCATIONS WITH A JET AXIS OVERHEAD IN STIFF SW
FLOW ALOFT. SFC WINDS MAY STAY E TO NE AT KCLT THROUGH THE
PERIOD...WHILE A BRIEF ADJUSTMENT TO SE IS EXPECTED AT THE OTHER
SITES. A STRATOCUMULUS LAYER WILL LIKELY MAKE A RUN TOWARD KCLT LATE
TONIGHT...WITH VFR CIGS LIKELY TOWARD DAYBREAK. NO PRECIPITATION IS
EXPECTED AT ANY TAF SITES DURING THE PERIOD...BUT ISOLATED SHOWERS
MAY APPROACH KAVL TOWARD 18Z MONDAY. MOIST GROUND COULD LEAD TO SOME
PATCHY SHALLOW FOG OVERNIGHT FROM KAVL TO KHKY...BUT WILL NOT
ADVERTISE IN THE TAFS JUST YET SINCE IT IS NOT SUPPORTED BY MOS OR
THE SOUNDINGS.
OUTLOOK...VFR CONDITIONS ARE EXPECTED THROUGH MON NIGHT AS HIGH PRES
BUILDS OVER TO THE N. RAIN AND WIDESPREAD LOW CIGS AND VSBYS ARE
EXPECTED TUE THROUGH EARLY WED AS A LOW PRESSURE SYSTEM FROM THE
WEST BRINGS ABUNDANT MOISTURE INTO THE AREA. DRYING IS EXPECTED MID
TO LATE WEEK.
&&
.GSP WATCHES/WARNINGS/ADVISORIES...
GA...NONE.
NC...NONE.
SC...NONE.
&&
$$
SYNOPSIS...DEO
NEAR TERM...HG
SHORT TERM...CSH
LONG TERM...DEO
AVIATION...HG
