FXUS62 KGSP 150741
AFDGSP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
241 AM EST TUE DEC 15 2009
.SYNOPSIS...
STRONG HIGH PRESSURE WILL BUILD IN FROM THE MISSISSIPPI VALLEY
TODAY...THEN GRADUALLY WEAKEN INTO THE SECOND HALF OF THE WEEK. LOW
PRESSURE WILL DEVELOP OVER THE GULF LATE IN THE WEEK AND CROSS
FLORIDA IN THE WEEKEND.
&&
.NEAR TERM /THROUGH TONIGHT/...
AFTER A FOGGY START EARLY THIS MRNG THE COLD FRONT WILL MOVE ACROSS
THE MTNS...THEN THROUGH THE PIEDMONT THIS AFTN. KEPT MENTION OF
LIKELY SHWRS SW CWA EARLY...TAPERING TO SLIGHT CHC N AND E...THEN
MAINLY JUST A CHC ACROSS THE S ZONES FROM AROUND DAYBREAK INTO EARLY
AFTN. A SLIGHT CHC WILL CONT THRU THE EVE OVER THE MTNS IN NW
UPSLOPE FLOW WITH SNOW PSBLY MIXING IN BEFORE PRECIP ENDS. LINGERING
LOW CLOUDS AND JET CIRRUS THIS AFTN WILL LIMIT INSOLATION SOMEWHAT
BUT STRONGER COLD ADVECTION WILL BE WELL BEHIND THE FRONT AND WITH
NW DOWNSLOPE FLOW...STILL EXPECT MAX TEMPS TO WARM INTO THE L60S N
AND CNTRL PIEDMONT WITH A FEW M60S S AND MAINLY L-M50S MTNS. HIGH
PRES BUILDS IN TONIGHT. WITH LOWERING THKNS VALUES EXPECT LOWS IN
THE M-U30S AT THE LOWER ELEVS...M20S-L30S MTNS.
&&
.SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
AS OF 135 AM TUESDAY...DRY/CONFLUENT UPPER FLOW OVER THE EASTERN
CONUS WILL MAKE FOR A VERY QUIET SHORT TERM...AS CANADIAN HIGH
PRESSURE RIDGE DOMINATES IN THE LOW LEVELS. THE ONLY ITEM OF MILD
INTEREST IS THAT IT DOES APPEAR THAT A PERSISTENT ACTIVE SOUTHERN
STREAM (ALBEIT SUPPRESSED WELL SOUTH OF THE GULF COAST)...AIDED AND
ABETTED BY THE POSITION OF THE JET STREAM JUST TO OUR NORTH...MAY
ENSURE THAT PLENTY OF CIRRUS REMAINS OVER THE AREA THROUGH THE
PERIOD. THIS SHOULD ALLOW MAX TEMPS TO BE A BIT COOLER (NEAR
CLIMO)...AND LOWS A BIT WARMER (ALSO NEAR CLIMO) THAN THEY OTHERWISE
WOULD BE.
&&
.LONG TERM /FRIDAY THROUGH MONDAY/...
AS OF 145 AM TUESDAY...THE MEDIUM RANGE MODELS SEEM TO BE COMING
INTO A BIT BETTER AGREEMENT. SEEMS TO BE FAR GREATER CONFIDENCE
THAT THERE WILL BE SHARP HEIGHT FALLS DURING THE UPCOMING WEEKEND
WITH A DEEP UPPER TROUGH WHICH MAY LINGER INTO EARLY NEXT WEEK. TO
START THIS PERIOD...12Z FRIDAY...THE GFS...ECMWF AND GEM ALL HAVE A
SURFACE LOW OVER THE EASTERN GULF WHICH MOVES IN SOME FASHION OVER
FLORIDA. THE GFS AND ECMWF HAVE THIS LOW MOVING EAST NORTHEAST AND
JUST FAR ENOUGH AWAY TO KEEP PRECIP OUT OF OUR FORECAST AREA. I
RAISED THE POP TO 14 IN SOUTHEAST ZONES FRIDAY AND FRIDAY NIGHT JUST
TO SAY PRECIP IS NOT FAR AWAY TO THE SOUTHEAST. AS WE GET INTO THE
WEEKEND...THE GFS IS MORE PROGRESSIVE WITH THE UPPER TROUGH MOVING
OVER OUR AREA THEN OUT FOR THE START OF NEXT WEEK. BOTH OF THESE
MODELS HAVE SPOKES OF ENERGY ROTATING AROUND THE BRINGING IN
NORTHWEST FLOW MOISTURE UP AGAINST THE NC MOUNTAINS WITH A PROLONGED
PERIOD OF SNOW SHOWERS. THE ECMWF WOULD KEEP WELL BELOW NORMAL
TEMPERATURES ACROSS OUR AREA INTO THE MIDDLE OF NEXT WEEK. THE GFS
HAS THE HEIGHTS BEGINNING TO RISE FROM THE WEST ON MONDAY. DID NOT
MAKE MANY CHANGES TO PREVIOUS FORECAST BUT DID LOWER TEMPERATURES A
BIT MORE AS THE EFFECTS OF THE TROUGH ENTRENCHES ITS WAY OVER OUR
AREA. ADDED SLIGHT CHANCE POPS FOR SNOW SHOWERS ALONG THE NC/TN
BORDER NORTH OF ASHEVILLE MONDAY AND MONDAY NIGHT.
&&
.AVIATION /08Z TUESDAY THROUGH SATURDAY/...
KCLT AND ELSEWHERE...DENSE FOG AGAIN OVERNIGHT. FOG/STRATUS SHOULD
BEGIN TO LIFT BY LATE MRNG AS A COLD FRONT CROSSES THE AREA...BECMG
VFR LATER THIS AFTN WITH BETTER NW DOWNSLOPE WINDS BEHIND FRONT. LOW
CLOUDS WILL LINGER AT KAVL IN MOIST NW UPSLOPE FLOW.
OUTLOOK...UNRESTRICTED CIG/VSBY EXPECTED WED-FRI IN DRY AIRMASS
BEHIND COLD FRONT. A WEAK SYSTEM APPROACHES FROM THE W SAT...
POSSIBLY BRINGING LOWER CIG/VSBY AND SCT RAIN OR SNOW SHOWERS TO THE
MTNS.
&&
.GSP WATCHES/WARNINGS/ADVISORIES...
GA...NONE.
NC...NONE.
SC...NONE.
&&
$$
SYNOPSIS...DEO
NEAR TERM...RB
SHORT TERM...JDL
LONG TERM...DEO
AVIATION...RB
