FXUS62 KGSP 270554
AFDGSP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
1254 AM EST FRI NOV 27 2009
.SYNOPSIS...
HIGH PRESSURE WILL BE IN CONTROL DURING THE WEEKEND AND INTO EARLY
MONDAY. ANOTHER COLD FRONT WILL ARRIVE LATE MONDAY AND MONDAY
NIGHT. AS THAT FRONT STALLS OUT...LOW PRESSURE WILL TRACK NORTHEAST
ALONG THE FRONT FROM THE GULF TOWARD OUR AREA IN MID WEEK.
&&
.NEAR TERM /THROUGH TODAY/...
COINCIDENT WITH TROF AXIS PASSAGE...SKIES WILL BE CLEARING ALONG
AND EAST OF THE I-77 CORRIDOR THRU LATE EVENING. REGIONAL 88D LOOPS
INDICATE PLUME OF PCPN EXTENDING SE FROM LK MICHIGAN...MAKING A BEE
LINE FOR NW NC. COINCIDENT WITH THE ENCROACHMENT OF DEEPER RH...A
PERIOD OF MODERATE NW FLOW IS STILL EXPECTED INTO FRIDAY MORNING. 00
UTC NAM RESPONSE HAS BACKED OFF ON SNOW TOTALS A TAD...BUT
ESSENTIALLY...STILL SUPPORTS LOCALIZED ACCUMS UP TO 3 INCHES ACRS
THE HIGHER TERRAIN AND WESTERN SLOPES. FURTHER DOWN THE
CHAIN...AVAILABLE MOISTURE WILL BE EXPECTEDLY LESS AND DIMINISHES
QUICKLY BY DAYBREAK. WOULD EXPECT AN INCH...PERHAPS TWO WILL BE
ALL WE ARE ABLE TO MUSTER ALONG THE TENN LINE...WITH ACCUMS
RAPIDLY DIMINISHED HEADING TOWARD THE BLUE RIDGE. ALL IN ALL...
CERTAINLY DO NOT EXPECT ANYTHING WORSE THAN WE ARE CURRENTLY
ADVERTISING...AND WILL UPDATE WSW SHORTLY. WITH ABOUT 45 KTS
OF 85H FLOW AND A NOMINAL AMOUNT OF ADDITIONAL LLVL CAA
OVERNIGHT...MOUNTAIN GUSTS SHOULD REMAIN WITHIN WIND ADVISORY
CRITERIA.
THE UPSLOPE MOISTURE IS STILL EXPECTED TO RAPIDLY DESICCATE
FRIDAY MORNING BRINGING A FAST END TO ANY ACCUMULATING SNOW SHOWER
THREAT. WITH DEEPENING MIXING...BREEZY TO WINDY CONDITIONS WILL
DEVELOP INTO THE PIEDMONT AS MAX TEMPS ARE EXPECTED TO BE BELOW
CLIMO.
&&
.SHORT TERM /TONIGHT THROUGH MONDAY NIGHT/...
AS OF 200 PM THU...ANY RESIDUAL NW FLOW MOISTURE WILL HAVE
DISSIPATED BY FRIDAY EVENING...HOWEVER...A TIGHT PRESSURE GRADIENT
WILL PERSIST ALONG WITH COLD ADVECTION ACROSS THE NRN NC MTNS. THE
WIND ADVISORY WILL BE EXTENDED FOR THE NRN MTNS UNTIL MIDNIGHT.
A FLAT RIDGE OF HIGH PRESSURE WILL BUILD ACROSS THE SOUTHEAST ON
SATURDAY. GOOD INSOLATION AND A NW DOWNSLOPING FLOW WILL ALLOW
PIEDMONT TEMPS TO WARM INTO THE 60S...WITH GENERALLY 50S ACROSS MOST
OF THE MTNS.
A POTENT SOUTHERN STREAM UPPER JETLET EMERGING FROM THE BAJA
PENINSULA WILL MOVE OVER THE SRN PLAINS ON SUNDAY...AND THEN RIDE UP
OVER THE FLATTENING SE RIDGE ON MONDAY. MOISTURE FROM THIS SRN
PINEAPPLE EXPRESS WILL INCREASE RAPIDLY ON SUNDAY ALONG A COLD FRONT
PUSHING SOUTHEAST INTO THE OH VALLEY...WITH MAINLY JUST AN INCREASE
IN MID AND HIGH CLOUDS FOR OUR FORECAST AREA. A DIGGING NRN STREAM
SYSTEM WAVE OVER THE GREAT LAKES WILL THEN PUSH THE FRONTAL ZONE
INTO THE FORECAST AREA MONDAY THROUGH MONDAY NIGHT. WILL RAMP CHC TO
LIKELY POPS UP FROM THE WEST ON MONDAY...WITH SHOTGUN SOLID CHANCES
ACROSS THE ENTIRE AREA WITH A LIKELY FROPA MONDAY NIGHT. THE GFS
APPEARS A LITTLE TOO AGGRESSIVE WITH COLD AIR BEHIND THE FRONT LATE
MONDAY NIGHT...BUT A HIGH ELEVATION RAIN/SNOW SHOWER MIX IN THE NW
FLOW IS POSSIBLE.
&&
.LONG TERM /TUESDAY THROUGH THURSDAY/...
AS OF 215 PM THURSDAY...THE GFS AND ECMWF ARE IN GOOD AGREEMENT IN
BRINGING DRIER AIR INTO THE REGION ON TUESDAY AS HIGH PRESSURE
FOLLOWS BEHIND A NORTHERN STREAM TROUGH. THE SOURCE REGION OF THE
HIGH APPEARS TO BE SOMEWHERE OVER THE NRN PACIFIC. EVEN THOUGH IT
WILL SEE SOME DRYING AS IT CROSSES THE CONUS...I DON/T THINK IT WILL
HAVE SUPER LOW DEWPOINTS. THIS IS IMPORTANT AS A SRN STREAM UPPER
LOW WILL QUICKLY EJECT ACROSS THE SRN MS RIVER VALLEY ON WED/THU IN
RESPONSE TO SIGNIFICANT HEIGHT FALLS OVER THE NRN TIER OF THE US.
AS THE LOW EJECTS...THE HIGH WILL TAKE ON A DAMMING CONFIGURATION
ACROSS THE REGION ON WEDNESDAY. ATTM...THOSE DEWPOINTS JUST DON/T
LOOK AS THOUGH THEY WILL BE COLD ENOUGH FOR MUCH IN THE WAY OF MIXED
PCPN. THE GFS BUFKIT SOUNDINGS SHOW A STRONG WARM NOSE AS THE LOW
EJECTS...WHICH DEFINITELY MEANS NO SNOW. THE EC IS EVEN FARTHER WEST
WITH THE LOW...IMPLYING AN EVEN WARMER AIRMASS. WE WOULD NEED THE
COLD AIR DAMMING PROCESS TO LOCK IN COLD DRY AIR NEAR THE SFC FOR
ANY KIND OF MIX. WITH THOSE MODIFIED PACIFIC DEWPOINTS...AND THE
FAIRLY TRANSITORY NATURE OF THE RIDGE...THIS APPEARS TO BE UNLIKELY.
OF COURSE...A BRIEF PERIOD OF MIX OVER THE MTN VALLEYS IS ALWAYS
POSSIBLE...BUT THAT/S SOMETHING TO REFINE CLOSER TO THE EVENT.
THURSDAY SHOULD SEE IMPROVING CONDITIONS AND FAIRLY MILD TEMPS AS
ALL THE COLD AIR WILL BE BACK OVER THE PLAINS UNDER THE AMPLIFYING
TROUGH OVER THE CENTRAL PART OF THE COUNTRY.
&&
.AVIATION /06Z FRIDAY THROUGH TUESDAY/...
AT KCLT AND ELSEWHERE...LLVL MOISTURE WILL REMAIN ACROSS THE NC MTNS
THROUGH MID DAY FRIDAY. EAST OF THE MTNS...SKY COVER SHOULD REMAIN
CLEAR TO MOSTLY CLEAR WITH P6SM VISIBILITY THROUGH THE TAF PERIOD.
THE MAIN FORECAST CHALLENGE WILL REMAIN WITH THE WIND DIRECTION AND
SPEED. OVERALL...THE PRESSURE PATTERN WILL FEATURE A SFC RIDGE EAST
OF THE MTNS WITH A NARROW LEE TROF. THIS PATTERN WILL YIELD NW WINDS
ACROSS THE MTNS...LIKELY GUSTING TO 25-30 KTS WITH ACTIVE DAYTIME MIXING.
EAST OF THE MTNS...DIRECTIONS SHOULD FAVOR A WEST TO SOUTHWEST
DIRECTION...WINDS WILL LIKELY BECOME GUSTY BY MID MORNING AND WILL
REMAIN UNTIL SUNSET. AT KCLT...A CROSSWIND WILL REMAIN AROUND 260
DEGREES WITH GUSTS NEAR 20 KTS FROM 15Z UNTIL 22Z.
OUTLOOK...VFR CONDITIONS ARE EXPECTED THROUGH SUNDAY. RESTRICTIONS
ASSOCIATED WITH PRECIPITATION COULD OCCUR ON MONDAY INTO TUESDAY.
&&
.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 MIDNIGHT EST TONIGHT 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...DEO
NEAR TERM...CSH/JDL
SHORT TERM...HG
LONG TERM...MCAVOY
AVIATION...NED
