FXUS62 KGSP 291917
AFDGSP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
217 PM EST SUN NOV 29 2009
.SYNOPSIS...
HIGH PRESSURE WILL WEAKEN AND MOVE OFF THE EAST COAST BY MONDAY
MORNING AS A COLD FRONT APPROACHES FROM THE WEST. THIS FRONT WILL
CROSS THE AREA ON MONDAY WITH A BRIEF PERIOD OF HIGH PRESSURE
RETURNING TO THE REGION ON TUESDAY. THE NEXT SYSTEM IS THEN EXPECTED
TO AFFECT NORTHEAST GEORGIA AND THE WESTERN CAROLINAS FROM THE SOUTH
STARTING ON WEDNESDAY.
&&
.NEAR TERM /THROUGH MONDAY/...
SW WINDS AND INCREASING CLOUDS IN ADVANCE OF VIGOROUS FRONTAL SYSTEM
SHOULD RESULT IN A RELATIVELY WARM NIGHT TONIGHT...WITH MINS
EXPECTED TO AVERAGE AROUND 10 DEGREES ABOVE NORMAL. A BAND OF
SHOWERS WILL ACCOMPANY THE FRONT INTO THE REGION...LIKELY REACHING
THE SOUTHWEST NC MTNS BY AROUND DAYBREAK. LIKELY POPS WILL BE
CARRIED IN THOSE AREAS WELL AFTER MIDNIGHT.
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 /MONDAY NIGHT 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 /19Z SUNDAY THROUGH FRIDAY/...
AT KCLT AND ELSEWHERE...SCT-BKN MID/HIGH LEVEL CLOUDS WILL CONTINUE
TO AFFECT THE AREA THROUGH THE EVENING HOURS. SW WINDS OF AROUND 10
KT CAN BE EXPECTED THIS AFTERNOON...BEFORE A SLIGHT DECREASE THIS
EVENING. OTHERWISE...FRONTAL BOUNDARY WILL APPROACH THE AREA FROM
THE TENN VALLEY OVERNIGHT. THIS WILL BRING SHOWERS TO AREAS AROUND
KAVL BY AROUND DAYBREAK...WHICH WILL THEN PROGRESS EAST INTO THE
FOOTHILLS AND PIEDMONT DURING THE MORNING HOURS. MVFR VISBY/CIGS
COULD ACCOMPANY PRECIP...BUT BEING THAT THIS WOULD OCCUR DURING THE
OUTLOOK PERIOD...WILL NOT INCLUDE ANY RESTRICTIONS ATTM.
OUTLOOK...THE FRONT WILL PUSH EAST OF THE AREA MONDAY AFTERNOON.
GUSTY WEST-NORTHWEST WINDS WILL DEVELOP BEHIND THE FRONT AND LINGER
INTO MONDAY NIGHT. DRY HIGH PRESSURE WILL BUILD OVER THE REGION ON
TUESDAY. TUESDAY NIGHT THROUGH WEDNESDAY NIGHT...A SIGNIFICANT AREA
OF LOW PRESSURE WILL LIFT FROM THE NRN GULF OF MEXICO ACROSS THE
WESTERN CAROLINAS. WIDESPREAD RA AND CEILING/VIS RESTRICTIONS WILL
ACCOMPANY THE PASSAGE OF THE LOW. CONDITIONS SHOULD BEGIN TO IMPROVE
EARLY THURSDAY...WITH DRY WEATHER EXPECTED FRIDAY.
&&
.GSP WATCHES/WARNINGS/ADVISORIES...
GA...NONE.
NC...NONE.
SC...NONE.
&&
$$
SYNOPSIS...JPT
NEAR TERM...JDL
SHORT TERM...SBK
LONG TERM...CSH
AVIATION...JDL
