FXUS62 KGSP 051521
AFDGSP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
1021 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 SNOW SHIELD MOVING NE FROM ERN TN ACROSS THE FAR WRN NC MTNS IS
LIKELY PRODUCING THE BEST SNOWFALL RATES OF THE EVENT SO FAR AT
PRESENT. FORCING WITH THE MAIN UPPER WAVE TO THE WEST WILL LIKELY
CONTINUE THROUGH 18Z ACROSS THE NRN HALF OF THE WARNING/ADVISORY
AREA...HOWEVER...EXTREME SRN SECTIONS SHOULD SEE PRECIPITATION
RAPIDLY TAPER OFF THROUGH NOON. WILL THUS CANCEL THE ADVISORY FOR
GRAHAM...WITH 1 INCH TOTALS REPORTED IN A FEW LOCATIONS THUS
FAR...AND FOR MACON...WHERE GENERALLY FLURRIES TO A DUSTING HAS BEEN
REPORTED.
WE COULD STILL SEE SOME LINGERING BLUE RIDGE FORCING THROUGH THE
AFTERNOON HOURS AS FRONTOGENESIS SETS UP. WILL BE A BIT SLOWER TO
CANCEL THE NRN HALF OF THE HAZARD AREA THIS AFTERNOON UNTIL WE
CONFIRM THE SNOWFALL IS ENDING.
HAVE ALREADY MADE MINOR TWEAKS TO TEMPERATURES IN LINE WITH THE
LATEST OBS...AND SNOW AMOUNTS HAVE BEEN REDUCED SLIGHTLY. WILL KEEP
THE 4 TO 5 INCH AMOUNTS GOING ALONG THE HIGHER NRN MTN RIDGES
HOWEVER...AS SNOW EFFICIENCY IS INCREASING WITH FALLING TEMPS.
CLEARING IS EXPECTED TONIGHT WITH SUBFREEZING TEMPS THROUGHOUT.
BLACK ICE WILL BE A CONCERN IN AREAS AFFECTED BY THE SNOWFALL. A
WINTER WEATHER ADVISORY FOR SOME MOUNTAIN LOCATIONS COULD BE NEEDED
OVERNIGHT.
&&
.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 /16Z SATURDAY THROUGH WEDNESDAY/...
KCLT AND ELSEWHERE...IFR CIGS HAVE DEVELOPED AT KCLT IN LIGHT RAIN
AND DRIZZLE...AND KHKY WILL LIKELY SEE IFR AT TIMES AS WELL. KAVL IS
NOW IN THE IFR RANGE...AND SHOULD THROUGH 18Z UNTIL THE SNOW STOPS.
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 21 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-
053-059-063>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...HG
SHORT TERM...CSH
LONG TERM...DEO
AVIATION...HG/MCAVOY
