FXUS62 KGSP 060809
AFDGSP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
309 AM 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/...
HIGH PRESSURE WILL BUILD INTO THE REGION TODAY...AND TAKE ON A COLD
AIR DAMMING CONFIGURATION TONIGHT. AN ACTIVE SRN STREAM WILL SEND A
COUPLE SHORT WAVES ACROSS THE AREA OVER THE NEXT 24 HOURS. THIS WILL
MAINLY RESULT IN HIGH CLOUDS TODAY...BUT MORE SIGNIFICANT CLOUD
COVER COULD DEVELOP LATE TONIGHT AS UPGLIDE DEVELOPS OF THE
WEDGE...PARTICULARLY ALONG AND SOUTH OF I-85. THE GFS BUFKIT
SOUNDINGS EVEN HAVE SOME LIGHT PCPN OVER THE CHARLOTTE METRO AREA
DURING THE LATE NIGHT HOURS. I HAVE KEPT THE INCREASING CLOUD COVER
TREND...BUT I DIDN/T ADD ANY DRIZZLE AS THE NAM HAD A MUCH SHALLOWER
LAYER OF HIGH RH/S.
PATCHY BLACK ICE WILL BE POSSIBLE THROUGH MID-MORNING IN THE NC
MTNS...PARTICULARLY NEAR THE TN LINE WHERE A COUPLE INCHES OF SNOW
FELL YESTERDAY. WE HAVE A SPECIAL WEATHER STATEMENT OUT
HIGHLIGHTING THIS FACT.
&&
.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 /08Z SUNDAY THROUGH THURSDAY/...
KCLT...HIGH PRESSURE WILL BUILD INTO THE REGION TDA. WINDS WILL BE
NORTHEAST THIS MORNING...BUT SHOULD TURN OUT OF THE SE A LITTLE
AFTER NOON. THE WINDS WILL TURN BACK OUT OF THE NE AFTER SUNSET AS
THE HIGH STARTS TO TAKE ON MORE OF A COLD AIR DAMMING CONFIGURATION.
HIGH CLOUDS WILL GRADUALLY INCREASE THROUGH THE PERIOD.
ELSEWHERE...WINDS WILL BE LIGHT...BUT GENERALLY OUT OF THE NORTHEAST
THIS MORNING. WINDS WILL VEER TO SOUTHEAST AROUND NOON...BUT THEN
TURN BACK TO THE NORTHEAST THIS EVENING AS COLD AIR DAMMING
DEVELOPS. HIGH CLOUDS WILL THICKEN AND LOWER THROUGH THE PERIOD.
MVFR FOG IS EXPECTED TO DEVELOP AT KHKY AS THEY HAD MORE RAINFALL
THAN OTHER SITES ACROSS THE REGION ON SAT. KAVL SHOULD SEE A PERIOD
OF IFR FOG THIS MORNING...THOUGH I DIDN/T GO AS PESSIMISTIC AS THE
PREVIOUS PACKAGE.
OUTLOOK...A PERIOD OF LOW CIGS IS POSSIBLE MONDAY MORNING AS RETURN
FLOW BRINGS MOISTURE INTO THE REGION. GENERALLY VFR CONDITIONS ARE
THEN EXPECTED THROUGH EARLY TUE. RAIN AND WIDESPREAD LOW CIGS AND
VSBYS ARE EXPECTED LATE TUE THROUGH WED AS LOW PRESSURE CROSSES THE
REGION.
&&
.GSP WATCHES/WARNINGS/ADVISORIES...
GA...NONE.
NC...NONE.
SC...NONE.
&&
$$
SYNOPSIS...DEO
NEAR TERM...MCAVOY
SHORT TERM...CSH
LONG TERM...DEO/JDL
AVIATION...MCAVOY
