FXUS62 KGSP 300618
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
118 AM EST MON NOV 30 2009

.SYNOPSIS...
A COLD FRONT WILL APPROACH THE CAROLINAS FROM THE WEST ON MONDAY. 
AFTER THIS FRONT MOVES OVER THE AREA...A BRIEF PERIOD OF HIGH 
PRESSURE WILL RETURN TO THE REGION ON TUESDAY. A SURFACE LOW IS THEN 
EXPECTED TO MOVE OVER THE REGION FROM THE GULF OF MEXICO LATE 
TUESDAY INTO WEDNESDAY FOLLOWED BY HIGH PRESSURE BUILDING BACK IN 
LATE IN THE WEEK.

&&

.NEAR TERM /THROUGH TODAY/...
AN AREA OF LIGHT RAIN AND EVEN A FEW HEAVIER SHOWERS HAS JUST 
STARTED TO MOVE INTO THE SOUTHWEST MTNS OF NC AND WILL SOON ENTER NE 
GA. THE RUC HAS H5 NVA OVER THIS AREA...AND THE NEITHER THE NAM OR 
THE GFS HAS MUCH ASCENT IN THIS AREA. HOWEVER...THE FAIRLY NARROW 
BAND OF PCPN IS FILLING IN FARTHER TO THE WEST WHERE THE LLVL WARM 
ADVECTION IS A LITTLE STRONGER. I/M TAKING THIS AS A SIGN THAT THE 
PCPN WILL CONTINUE FOR A WHILE IN THESE AREAS. I/VE UPPED POPS A 
FAIR AMOUNT THROUGH MIDNIGHT AHEAD OF THE BAND OF RAIN. I DIDN/T 
TAKE HIGHER POPS MUCH FARTHER EAST THAN THE WRN FOOTHILLS. 
HOWEVER...AT IT/S PRESENT RATE OF MOVEMENT...ANOTHER UPDATE MAY BE 
NEEDED LATER THIS EVENING. 

POPS RAMP UP TO HIGH LIKELY TO CATEGORICAL ACROSS ALL OF THE 
MOUNTAINS AND ADJACENT FOOTHILLS MONDAY MORNING. ALTHOUGH PRECIP 
WILL COME AND GO QUICKLY...DEEP FORCING IN THE FORM OF UPPER LEVEL 
DIVERGENCE IN THE RRQ OF 120+ KT UPPER JET STREAK AND STRONGLY 
ADVECTIVE MID-LEVEL SW TROUGH SHOULD RESULT IN GOOD PRECIP RATES 
ACROSS THE WESTERN MOUNTAINS OF NC...WHERE QPF IS EXPECTED TO RANGE 
FROM .5-.75 INCH. LOW LEVEL FORCING QUICKLY WANES...IN RESPONSE TO 
VEERING PRE-FRONTAL FLOW...AS THE FRONT PASSES EAST OF THE BLUE 
RIDGE. HOWEVER...UPPER FORCING REMAINS QUITE IMPRESSIVE...SO LIKELY 
POPS WILL BE CARRIED INTO THE PIEDMONT DURING THE AFTERNOON. MUCH 
COOLER AIR WILL ADVECT QUICKLY INTO THE REGION MONDAY AFTERNOON... 
WITH TEMPS EXPECTED TO SLOWLY FALL DURING THE AFTERNOON ACROSS THE 
MTNS. THERE WILL ALSO BE A QUICK SHOT OF VIGOROUS NW/UPSLOPE FLOW 
DURING THE AFTERNOON. HOWEVER...CONSENSUS MODEL SOLUTIONS KEEP THE 
SNOW LEVEL ABOVE THE HIGHEST PEAKS PRIOR TO 00Z.

&&

.SHORT TERM /TONIGHT THROUGH WEDNESDAY NIGHT/...
AS OF 215 PM SUNDAY...THE MODELS AGREE WELL WITH THE TIMING AND 
STRENGTH OF THE MP HIGH BUILDING INTO THE REGION RATHER QUICKLY 
AFTER 06Z TUE. BEFORE THAT...THE NC MTNS HAVE BEEN LEFT WITH 
LINGERING ISOLATED SHOWERS A MIXED P/TYPE AS H85 TEMPS LOWER TO 
ABOUT -3 C. TUE SHOULD BE A VERY NICE DAY WITH THE POST FRONTAL 
AIRMASS MODIFYING EFFICIENTLY IN GOOD SUBSIDENCE AND PLENTY OF 
INSOLATION. EXPECT TEMPS RIGHT AROUND OR PERHAPS A FEW DEGREES ABOVE 
NORMAL. 

THE PATTERN REMAINS PROGRESSIVE AS A SOUTHERN STREAM LOW LIFTS NORTH 
OUT OF THE GOM WED. THE 12Z GFS IS ABOUT 12 HRS FASTER WITH THIS 
SCENARIO THAN ALL THE OTHER OP GUIDANCE...EVEN THE FASTER SREF. 
THEREFORE...CHANCE POPS HAVE BEEN DELAYED ABOUT 6 HRS...YET A QUICK 
RAMP UP TO CATEGORICAL POPS IS NOW ADVERTISED ACROSS ALL ZONES 
THROUGH THE DAY WED. THERE ARE SUBTLE PLACEMENT DIFFERENCES WRT TO 
THE SFC LOW LOCATION AND EVOLUTION...BUT NOT ENOUGH TO BELIEVE THE 
BEST LIFT AND MOISTURE FLUX WILL AVOID THE AREA. PWATS ARE EXPECTED 
TO BE AROUND 250 PERCENT OF NORMAL AND THE SOUNDINGS INDICATE 
SATURATION THROUGH A VERY DEEP LAYER. THUS...QPF AMOUNTS COULD 
CREATE A FLASH FLOOD THREAT GIVEN THE HIGH AMOUNTS PRECIP IN A 
RELATIVELY SHORT AMOUNT OF TIME. RIGHT NOW...THE STORM TOTAL PRECIP 
IS HOVERING AROUND 1.5 INCHES IN MOST PLACES WITH NEARLY 2 INCHES IN 
THE SOUTHERN MOST ZONES. THIS IS ABOUT A HALF AN INCH LOWER THAN HPC 
GUIDANCE AND WITH A POSSIBLY SLOWER MOVING SYSTEM...HIGHER QPF 
AMOUNTS ARE CERTAINLY POSSIBLE. THIS WILL BE A SYSTEM TO WATCH AND 
KEEP TRACK OF THE LATEST DEVELOPMENTS. 

A LITTLE SLOWER EXIT OF THE SYSTEM IS EXPECTED BASED ON THE 
LATEST MODEL DISAGREEMENTS...SO HIGH END POPS WERE MAINTAINED ACROSS 
THE NORTHERN ZONES THROUGH WED NIGHT. H85 TEMPS DROP TO AROUND -6 C 
AND LLVL TKNS DROP TO AROUND 129 DM DURING THE THE LATTER HALF OF 
WED NIGHT ACROSS THE W/RN NC MTNS...SO A MIX OF -SN/RA HAS 
MAINTAINED DURING THIS TIME. 

EXPECT MAX TEMPS ABOUT 10 DEGREES BELOW NORMAL WED WITH LITTLE IN 
THE WAY OF SUNSHINE...AND PRECIP DRAGGING WILL ALSO HELP MAINTAIN 
COOLER TEMPS AT THE SFC. WITH THE DRY SLOT NOT MOVING IN UNTIL LATE 
MORNING...MINS SHOULD ONLY DROP OFF ABOUT 10 DEGREES FROM WED/S 
HIGHS...OR REMAIN ABOUT 5 DEGREES ABOVE NORMAL.

&&

.LONG TERM /THURSDAY THROUGH SUNDAY/...
AS OF 200 PM SUNDAY...THE CWFA IS STILL EXPECTED TO BE FIRMLY WITHIN 
ROBUST CIRCULATION OF DEEPENING AND DEPARTING SFC CYCLONE THURSDAY. 
LATEST HPC SOLUTION SUPPORTS 00 UTC ECMWF OF A SLOWER TRANSLATION
OF AFOREMENTIONED SYSTEM...AND WILL DELAY DRY SLOT ENCROACHMENT UNTIL
AFTERNOON. SCATTERED TO NUMEROUS WRAP-AROUND SHOWERS...WITH THE
PROBABILITY OF A TRANSITION TO SNOW SHOWERS IS ON TRACK FOR THE NC
MTNS AS THE DAY WEARS ON. ASSUMING TIGHT PRESSURE GRADIENT AND
DEVELOPING SUNSHINE WILL RESULT IN SOME DEGREE OF WIND ISSUES AS 
WELL. CONTINUED UPSLOPE SNOW SHOWERS REMAIN POSSIBLE THURSDAY NIGHT 
AS BLUSTERY AND INCREASINGLY CHILLY CONDITIONS DEVELOP REGIONWIDE.

EASTERN CONUS L/WV TO DEVELOP ON FRIDAY AS LLVL RIDGING BEGINS TO
NOSE EASTWARD. GENERALLY FAIR AND CONTINUED CHILLY CONDITIONS ARE
EXPECTED WITH MAX TEMPS 5-10 DEG F BELOW CLIMO. 

FOR NEXT WEEKEND...WITHIN SEASONALLY FAST UPPER FLOW...LLVL RIDGING 
IS PROGGED TO BUILD INTO AND THE ACRS THE REGION. WILL PLAN ON 
STICKING CLOSE TO THE HPC SOLUTION...FEATURING DRY AND CHILLY 
CONDITIONS.

&&

.AVIATION /06Z MONDAY THROUGH FRIDAY/...
AT KCLT AND ELSEWHERE...MID AND HIGH LEVEL CLOUDS AND SOUTHWESTERLY 
WINDS WILL CONTINUE THROUGH THE REST OF THE NIGHT. MODELS HAVE BEEN 
CONSISTENT WITH HANDLING A RAPIDLY APPROACHING COLD FRONT...WHICH 
SHOULD ARRIVE OVER THE MTNS AROUND SUNRISE AND MAKE STEADY PROGRESS 
EAST ACROSS THE WESTERN CAROLINAS. A BAND OF SHOWERS SHOULD 
ACCOMPANY THE FRONT WITH VISIBILITY EXPECTED TO BE MAINLY VFR...BUT 
THERE COULD VERY EASILY BE BRIEF PERIODS OF MVFR VISIBILITY IF 
HEAVIER SHOWERS SURVIVE THE TRIP OVER THE MTNS. CEILING SHOULD DROP 
INTO MVFR RANGE WITH THE SHOWER BAND BUT SOME IFR NOT OUT OF THE 
QUESTION. FOR NOW...WILL FORGO A TEMPO FOR THE LATE MORNING/EARLY 
AFTERNOON AND LEAVE THE PREVAILING CONDITION MVFR BECAUSE OF 
CEILING. THE FRONT SHOULD MAKE IT EAST OF KCLT BY 21Z AND DOWNSLOPE 
FLOW WILL DEVELOP BY LATE AFTN...CLEARING OUT THE LOW CLOUDS AS THE 
WINDS TURN OUT OF THE WEST NORTHWEST. AT KAVL THE WIND SHIFT WILL 
HAPPEN SEVERAL HOURS EARLIER WITH WINDS GUSTING OVER 20 KTS BY LATE 
IN THE DAY. VFR CONDITIONS PREVAIL BEHIND THE FRONT.

OUTLOOK...VFR CONDITIONS LATE MONDAY NIGHT AND TUESDAY. TUESDAY 
NIGHT THROUGH WEDNESDAY NIGHT...A STRONG AREA OF LOW PRESSURE WILL 
LIFT FROM THE NRN GULF OF MEXICO ACROSS THE WESTERN CAROLINAS. 
WIDESPREAD RAIN AND CEILING/VIS RESTRICTIONS WILL ACCOMPANY THE 
PASSAGE OF THE LOW. CONDITIONS SHOULD BEGIN TO IMPROVE EARLY 
THURSDAY...WITH VFR EXPECTED FRIDAY.

&&

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

&&

$$
SYNOPSIS...JPT
NEAR TERM...JDL/MCAVOY
SHORT TERM...SBK
LONG TERM...CSH
AVIATION...PM