FXUS62 KGSP 051128
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
628 AM EST SAT DEC 5 2009

.SYNOPSIS...
AN AREA OF LOW PRESSURE WILL MOVE NORTHEAST ALONG THE CAROLINA COAST 
TODAY.  EXPECT THIS LOW TO PULL AWAY FROM OUR REGION TONIGHT AND 
SUNDAY AS HIGH PRESSURE CONTROLS OUR WEATHER INTO MONDAY.  A FAST 
MOVING COLD FRONT WILL PUSH ACROSS THE REGION LATE MONDAY.  A STRONG 
LOW WILL DEVELOP OVER THE PLAINS STATES AND MOVE NORTHEAST TO THE 
GREAT LAKES ON WEDNESDAY AS THE ASSOCIATED COLD FRONT APPROACHES THE 
CAROLINAS AND GEORGIA FROM THE WEST.

&&

.NEAR TERM /THROUGH TONIGHT/...
THE TIMING AND EVOLUTION OF THE MTN SNOW EVENT STILL LOOKS TO BE ON 
TRACK. REGIONAL SATELLITE IMAGES SHOW A BAROCLINIC LEAF STRETCHING 
ACROSS ERN MS/AL/NW GA AND CNTRL TN ATTM. ON THE SOUTH AND EAST PART 
OF THE THIS AREA OF COOLER CLOUD TOPS...A FAIRLY LARGE AREA OF LIGHT 
TO MODERATE SNOW WAS FALLING OVER NRN AND CENTRAL MS. PCPN WAS ALSO 
BEGINNING TO DEVELOP OVER NW GA AND THE SW NC MTNS...THOUGH WE HAVE 
YET TO VERIFY WHAT TYPE OF PCPN THAT IS. 

SO FAR THE GFS IS DOING A GOOD JOB WITH THE THIS SYSTEM...AND 
THAT/S THE MODEL I/M PRIMARILY USING FOR THIS FORECAST. DEEP LAYER 
Q-VECTOR CONVERGENCE BECOMES MORE ORGANIZED THROUGH 12 UTC OVER THE 
WESTERN CAROLINAS AND NE GA IN ASSOCIATION WITH THE APPROACHING 
SHORT WAVE. WHILE IT/S STARTING TO MOVE NORTH OF THE REGION BY 18 
UTC...THE FORCING STILL LOOKS GOOD ACROSS THE CENTRAL AND NRN NC 
MTNS AND FOOTHILLS. AS THE PREVIOUS SHIFT MENTIONED...THE H8 LOW 
CENTER WILL CROSS SOUTH SE OF THE MTNS BETWEEN 12 AND 18 UTC...WHICH 
IS WHEN I EXPECT THE BEST FORCING AND HEAVIEST SNOW TO OCCUR. A DRY 
SLOT WILL WARP THROUGH NE GA...THE UPSTATE AND THE SRN NC PIEDMONT. 
THESE AREAS WILL BE TOO WARM FOR SNOW ANYWAY...BUT THEY MAY SEE 
LITTLE IN THE WAY RAIN EITHER. 

THE LATEST LAPS SOUNDINGS SHOW THE SNOW LEVEL TO BE AROUND 4000 
FEET...BUT THIS WILL FALL QUICKLY AS THE PCPN BEGINS...AND THE SNOW 
SHOULD REACH THE VALLEY FLOORS AROUND 12 UTC IF NOT SOONER. THE NAM 
AND SREF QPF IS STILL ON THE LOW SIDE WHILE THE GFS IS HIGHER. OWING 
TO THE GOOD FORCING OVER THE MTNS...AND THE PLUME OF UPSTREAM 
MOISTURE AND PRECIPITATION THAT IS ALREADY IN PLACE...I THINK THE 
HIGHER QPF MAKES SENSE. THIS KEEPS US QUITE CLOSE TO THE PREVIOUS 
SHIFT/S SNOWFALL NUMBERS WITH 1 TO 2 INCHES OVER THE HIGHER 
ELEVATIONS OF THE SRN MTNS...WITH 3 TO 5 INCHES LIKELY OVER THE NRN 
MTNS...AND SIMILAR AMOUNTS AT THE HIGHER ELEVATIONS OF THE CENTRAL 
MTNS.

I/VE LOWERED MIN TEMPS TONIGHT A COUPLE DEGREES...BLENDING IN THE 
COOP MOS. AS WE HAVE BEEN ADVERTISING...THIS WILL RESULT IN AREAS OF 
BLACK ICE LATER TONIGHT...PARTICULARLY OVER THE MTNS AND WRN 
FOOTHILLS.

&&

.SHORT TERM /SUNDAY THROUGH TUESDAY/...
AS OF 215 AM SATURDAY...SFC HIPRES TO BUILD COASTWARD THRU 
SUNDAY...AS SUNSHINE GETS INCREASINGLY FILTERED BY HIGH CLOUDS 
ADVECTING EASTWARD WITHIN THE FAST WSW FLOW ALOFT. WILL PLAN ON 
BLENDING INHERITED MAX TEMPS WITH THE COOLER MET NUMBERS...FOR HIGHS
ABOUT 2-4 DEG F BELOW CLIMO. EXPECTING AN INCREASE IN WAA FLOW
ABOVE THE SFC SUNDAY NIGHT IN ADVANCE OF FAST MOVING WEAK FRONTAL 
SYSTEM. WILL FAVOR NAM/SREF RESPONSE IN LIMITING SMALL SHOWER
CHANCES CLOSER TO THE FRONTAL ZONE WELL WEST OF THE MTNS AND
NEAR COASTAL FRONT. HENCE...SENSIBLE WX WILL BE LIMITED TO
A CONTINUED INCREASE IN CLOUDS WITH LITTLE CHANGE TO INHERITED
MIN TEMPS...WHICH ESSENTIALLY SUPPORT A MOS BLEND.

A WEAK FRONTAL PASSAGE REMAINS SLATED FOR MONDAY WITH THE BETTER
FORCING AND DEEPER RH MOISTURE ORIENTED ACRS THE MTNS...A PER
LATEST NAM/SREF. SCATTERED MTN SHOWERS...POSSIBLY IN THE FORM
OF A LIGHT WINTRY MIX DURING THE MORNING ARE PROBABLE...WITH
JUST ISOLATED ACTIVITY IN THE PIEDMONT. EVEN THE COOLER MET
NUMBERS WARRANT AN UPWARD NUDGE TO MAX TEMPS TO AROUND CLIMO.

WITH DECENT AGREEMENT AMONG THE 00 UTC GFS AND ECMWF MODEL MASS 
FIELDS...CONFIDENCE INCREASING THAT STRENGTHENING WAA PATTERN WILL 
RESULT IN STRATIFORM PCPN OVERSPREADING THE CWFA TUESDAY ATOP OF 
DAMMING SFC HIPRES AND HAVE RAISED POP ACCORDINGLY. WILL CONTINUE
TO ADVERTISE A DEGREE OF LIGHT WINTRY MIX...MAINLY ACRS THE MTNS 
DURING THE ONSET OF PCPN.

&&

.LONG TERM /TUESDAY NIGHT THROUGH FRIDAY/...
AS OF 210 AM SATURDAY...THE MEDIUM RANGE MODELS ARE IN GOOD 
AGREEMENT IN TAKING THE MILLER B SYSTEM NORTHEAST WITH THE HIGHEST 
AMOUNT OF MOISTURE OVER OUR FORECAST AREA TUESDAY NIGHT.  MOISTURE 
GRADUALLY DECREASES OVER THE FOOTHILLS AND PIEDMONT DURING THE DAY 
WEDNESDAY LEAVING JUST THE NC MOUNTAINS WITH NORTHWEST FLOW SNOW 
WEDNESDAY NIGHT.  THE GFS MAINTAINS THE NORTHWEST FLOW LONGER BUT 
DECREASES THE MOISTURE.  THE ECMWF DROPS THE NORTHWEST FLOW EARLIER 
BUT MAINTAINS THE MOISTURE INTO EARLY THURSDAY.  ANYWAY...MADE SMALL 
ADJUSTMENTS TO THE POPS AND SNOW GRIDS DURING THE WEDNESDAY NIGHT TO 
EARLY THURSDAY PERIOD.  AFTER HIGH PRESSURE CONTROLS THE WEATHER 
THURSDAY INTO FRIDAY...THE NEXT SYSTEM MOVES IN FROM THE WEST 
SPREADING MOISTURE IN FRIDAY NIGHT.  I DRASTICALLY DECREASED POPS IN 
THIS PERIOD ACCORDING TO MODELS AND TO BRING US IN AGREEMENT WITH 
THE NEIGHBORS.  LITTLE CHANGE IN TEMPERATURES AS THEY WILL BE WITHIN 
A FEW DEGREES OF NORMAL.

&&

.AVIATION /12Z SATURDAY THROUGH WEDNESDAY/...
KCLT AND ELSEWHERE...IFR CIGS AND VSBYS HAVE DEVELOPED AT KHKY AND 
KCLT SHOULD FOLLOW SUIT IN THE NEXT HOUR AS CONDITIONS ARE WORSENING 
BOTH TO THE WEST AND EAST OF THE AIRFIELD. KAVL SHOULD ALSO FALL 
INTO THE IFR RANGE SHORTLY AS RAIN CHANGES OVER TO SNOW. MVFR CIGS 
HAVE DEVELOPED OVER THE UPSTATE SITES. NORTHERLY WINDS WILL VEER TO 
NORTHWEST THIS AFTERNOON...EXCEPT AT KAND WHERE THEY WILL TURN OUT 
OF THE WEST. THE RAIN AND SNOW SHOULD END BETWEEN 18 AND 20 UTC 
ACROSS THE REGION...IF NOT SOONER. CIGS WILL QUICKLY LIFT AT THIS 
TIME AS WELL. 

SKIES WILL BE CLEAR OVERNIGHT WITH N TO NW WINDS BECOMING LIGHT AND 
VARIABLE. TEMPERATURES WILL QUICKLY FALL TO BELOW FREEZING 
OVERNIGHT...AND A FEW PATCHES OF BLACK ICE MAY DEVELOP ON RUNWAYS 
OVERNIGHT. 

OUTLOOK...DRY WEATHER IS EXPECTED SUNDAY. A WEAK FRONT WILL PASS 
MONDAY. DRY HIGH PRESSURE IS THEN EXPECTED AGAIN EARLY TUESDAY 
BEFORE OUR NEXT MAJOR SYSTEM MOVES IN FROM THE W TUE NIGHT-WED.

&&

.GSP WATCHES/WARNINGS/ADVISORIES...
GA...NONE.
NC...WINTER WEATHER ADVISORY UNTIL 8 PM EST THIS EVENING FOR NCZ051-
     053-058-059-062>065-501-503-505.
     WINTER STORM WARNING UNTIL 8 PM EST THIS EVENING FOR NCZ033-
     048>053-059-501-503-505.
SC...NONE.

&&

$$
SYNOPSIS...DEO
NEAR TERM...MCAVOY
SHORT TERM...CSH
LONG TERM...DEO/JDL
AVIATION...MCAVOY