000
FXUS62 KGSP 241106
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
606 AM EST TUE NOV 24 2009

.SYNOPSIS...
HIGH PRESSURE WILL LINGER OVER THE REGION INTO WEDNESDAY. A COLD
FRONT WILL CROSS THE AREA THURSDAY... FOLLOWED BY HIGH PRESSURE INTO
EARLY NEXT WEEK.

&&

.NEAR TERM /THROUGH TONIGHT/...
ALOFT...SW FLOW PATTERN WILL BEGIN TO AMPLIFY TODAY AS A CLOSED LOW
AND MID AND UPPER LEVEL TROF AXIS MOVES INTO THE UPPER MIDWEST. AT
THE SURFACE...WEAK AREA OF HIGH PRESSURE AND CONSIDERABLE LOW LEVEL
CLOUDINESS WILL PERSIST ACROSS THE FA WITH LIGHT NE FLOW THROUGH THE
AFTERNOON. FLOW WILL EVENTUALLY TURN MORE EASTERLY AND THEN SOUTH OF
EAST LATE IN THE NEAR TERM AS THE HIGH WEAKENS AHEAD OF AN
APPROACHING FRONT. FOR MOST OF THE DAY...925-850 MOISTURE WILL
LINGER BUT WITH NO LIFT WILL KEEP DRY FORECAST IN PLACE. THERE IS
SOME DEGREE OF ISENTROPIC LIFT TONIGHT BUT THAT SHOULD ONLY SERVE TO
REINFORCE THE LOW LEVEL OVERCAST ACROSS THE FA. TRICKY PART OF THE
FORECAST REVOLVES AROUND TEMPERATURES. LOW LEVEL THICKNESSES IMPROVE
FROM YESTERDAY BUT THE PERSISTENT STRATUS LAYER WILL HELP TO HOLD
TEMPS BACK. VIRTUALLY ALL GUIDANCE SOURCES HAVE COME IN WARMER THAN
THE INHERITED FORECAST. SINCE I LIKE FOR CLOUDY CONDITIONS TO STICK
AROUND FOR THE ENTIRE DAY...I HAVE COOLED FORECAST HIGHS TOWARD THE
SREF. THIS RESULTS IN HIGHS AROUND 55 TO 57 EVERYWHERE.

&&

.SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
AS OF 305 AM TUE...COLD AIR DAMMING ERODES EARLY WEDNESDAY AS WLY
LOW LEVEL FLOW DEVELOPS BEHIND A WEAK COLD FRONT MOVING THRU THE
AREA. MOISTURE WITH THIS SYSTEM IS VERY LIMITED AND LIFT IS WEAK
EVEN THOUGH A DECENT SHORT WAVE MOVES ACROSS THE AREA. THEREFORE...
HAVE GONE WITH A DRY FCST. HIGHS WARM TO A LITTLE ABOVE NORMAL AS
SKIES CLEAR AND WESTERLY FLOW DEVELOPS.

DEEP UPPER LEVEL LOW MOVES TOWARD THE AREA WED NITE. MDLS ARE
CONSISTENT IN KEEPING ANY MOISTURE ASSOCIATED WITH THIS SYSTEM TO
OUR NORTH AND WEST DURING THIS PERIOD. CONTINUED DRY FCST WITH LOWS
FALLING TO NEAR NORMAL.

A STRONG SHORT WAVE SWINGS AROUND THE UPPER LOW AND INTO THE AREA
THU. THIS PUSHES ANOTHER WEAK COLD FRONT THRU THE AREA. MOISTURE
FINALLY MOVES INTO THE AREA THU AFTERNOON. HOWEVER... BEST MOISTURE
REMAINS TO OUR NORTH AND WEST. WITH THE WEAK LIFT AND SLOWLY
INCREASING MOISTURE...HAVE GONE WITH THE MDL CONSENSUS AND DROPPED
POP BACK TO SLIGHT CHC FOR THE NC MTNS. LOW LEVEL TEMPS FALL ENUF
LATE IN THE DAY FOR SNOW TO POSSIBLY MIX IN WITH THE RAIN OVER THE
RIDGE TOPS. HIGHS AGAIN NEAR NORMAL.

DEEP NWLY FLOW DEVELOPS AS THE UPPER LOW MOVES EAST. ANOTHER STRONG
SHORT WAVE MOVES ACROSS THE AREA IN THE FLOW. THIS COMBINED WITH
UPPER DIVERGENCE AHEAD OF AN APPROACHING UPPER JET...WILL LEAD TO
DECENT LIFT. THIS WILL BE ON TOP OF THE UPSLOPE NOW FLOW LIFT. LOW
LEVEL MOISTURE INCREASES AS WELL. HAVE KEPT THE INCREASE IN POP TO
LIKELY OVER THE NORMAL NW FLOW AREAS. COLD AIR COMES RUSHING IN AS
WELL. THIS SHOULD HELP CHANGE ALL THE PRECIP TO SNOW FOR ALL AREAS
AFTER MIDNIGHT. IF THESE TRENDS HOLD...THEN THIS PERIOD WOULD BE THE
BEGINNING OF ANY HIGH ELEVATION ADV PERIOD WHEN ACCUMULATIONS WOULD
BEGIN. WINDS WILL ALSO INCREASE OVER THE MTNS. STILL LOOKS LIKE
STRONGEST LOW LEVEL WINDS WILL BE ABOVE THE MIXED LAYER. HAVE GUSTS
JUST BELOW ADV LEVEL AFTER MIDNIGHT. LOWS BELOW NORMAL ALL AREAS.

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
AS OF 230 AM EST TUESDAY...THE ECMWF AND GFS REMAIN IN REASONABLE
AGREEMENT WITH THEIR UPPER PATTERNS FROM FRIDAY THROUGH SUNDAY. A
CLOSED LOW OVER THE NORTHEAST ON FRIDAY MOVES OFF THE NEW ENGLAND
COAST ON SATURDAY...WHILE AN UPPER RIDGE MOVES ACROSS THE MS RIVER
VALLEY. ON SUNDAY THIS RIDGE REACHES THE APPALACHIANS...AND A TROUGH
DIGS OVER THE SOUTHWEST. ON MONDAY THE GFS BECOMES FASTER THAN THE
ECMWF WITH THIS TROUGH. HPC USED A COMPROMISE SOLUTION OF THE GFS
AND ECMWF UNTIL LATE IN THE PACKAGE...WHEN THE CANADIAN MODEL WAS
BLENDED IN.

ON FRIDAY OUR AREA WILL BE IN STRONG NORTHWEST FLOW BEHIND A
DEPARTING COLD FRONT...WITH AN ONGOING UPSLOPE FLOW SNOW EVENT ALONG
THE TN BORDER. SNOW DIMINISHES FRIDAY NIGHT...ENDING BY SATURDAY
MORNING...AS MOISTURE DECREASES AND THE PRESSURE GRADIENT RELAXES. A
DRY SURFACE RIDGE MOVES ACROSS THE SOUTHEAST ON SUNDAY. ON MONDAY A
COLD FRONT APPROACHES FORM THE WEST...WITH AN OPEN GULF SPREADING
MOISTURE INTO THE SOUTHERN APPALACHIANS TO SUPPORT PRECIPITAITON.

TEMPERATURES WILL BE JUST ABOVE MID WINTER VALUES ON FRIDAY IN
STRONG COLD ADVECTION...DESPITE DOWNSLOPE FLOW IN THE LEE.
TEMPERATURES MODERATE TOWARD NORMAL OVER THE WEEKEND AS THE UPPER
RIDGE ARRIVES...BUT WARMING HALTS MONDAY AS CLOUD COVER SPREADS OVER
THE AREA.

&&

.AVIATION /11Z TUESDAY THROUGH SATURDAY/...
AT KCLT...AN MVFR CEILING IS EXPECTED TO LINGER INTO MIDDAY...WHILE
LIGHT NORTHEAST WINDS CONTINUE. WINDS VEER TO THE SOUTHEAST THIS
EVENING. SEVERAL HOURS BEFORE DAWN WEDNESDAY CALM WINDS AND  MVFR
FOG ARE EXPECTED IN MOIST LOWER LEVELS...BUT MODEL GUIDANCE AND TIME
HEIGHTS SUPPORT A VFR CEILING.

ELSEWHERE...MORNING RESTRICTIONS WILL LINGER INTO MIDDAY...THEN VFR
IS EXPECTED FOR THE AFTERNOON. LIGHT NORTH NORTHEAST WINDS VEER TO
THE SOUTHEAST TODAY EAST OF THE MOUNTAINS...WHILE KAVL SHIFTS FROM
NORTH TO SOUTHEAST. AROUND MIDNIGHT MVFR CEILING AND VISIBILITY ARE
EXPECTED AT KAVL AS COOL AIR POOLS IN THE VALLEY. JUST BEFORE DAWN
MVFR FOG IS EXPECTED OUTSIDE THE MOUNTAINS...BUT WITH A VFR CEILING
SUPPORTED BY TIME HEIGHTS AND GUIDANCE. KAVL WILL BE TAKEN DOWN TO
IFR VISIBILITY AND LIFR CEILING AROUND DAWN...A CATEGORY ABOVE
GUIDANCE.

OUTLOOK...PERIODS OF MVFR MAY LINGER WEDNESDAY MORNING...WITH IFR OR
LOWER RESTRICTIONS IN MOUNTAIN VALLEYS. A COLD FRONT WILL BRING
BREEZY NORTHWESTERLY WINDS ON FRIDAY AND A FEW RESTRICTIONS IN
SHOWERS IN THE MOUNTAINS.

&&

.GSP WATCHES/WARNINGS/ADVISORIES...
GA...NONE.
NC...NONE.
SC...NONE.

&&

$$
SYNOPSIS...JAT
NEAR TERM...BSH
SHORT TERM...RWH
LONG TERM...JAT
AVIATION...JAT