771
FXUS62 KGSP 260829
AFDGSP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
329 AM EST THU NOV 26 2009
SYNOPSIS
A COLD FRONT WILL ARRIVE TODAY. HIGH PRESSURE WILL BE IN CONTROL
DURING THE WEEKEND AND INTO EARLY NEXT WEEK. ANOTHER COLD FRONT
WILL ARRIVE ON MONDAY.
NEAR TERM /THROUGH TONIGHT/
DENSE FOG HAS DEVELOP ACROSS MUCH OF WESTERN NC EAST OF THE
MOUNTAINS...AND INTO THE NORTHERN SC UPSTATE. THE DENSE FOG ADVISORY
WILL BE EXPANDED INTO THE SOUTHERN NC FOOTHILLS AND THE KGSP AREA.
A STRONG SHORTWAVE TROUGH WILL CROSS THE SOUTHERN APPALACHIANS
TODAY. MIXING THIS MORNING WILL ERODE THE FOG...WITH FEW CLOUDS
REMAINING UNTIL A COLD FRONT APPROACHES THE MOUNTAINS LATE IN THE
DAY. SMALL CHANCE POPS WILL BE CARRIED IN THE NORTHERN NC MOUNTAINS
THIS AFTERNOON...WITH SNOW STARTING ON THE HIGHEST PEAKS LATE THIS
AFTERNOON. THE MODELS SHOW SOME LOW LEVEL MOISTURE MOVING ACROSS THE
INTERSTATE 77 CORRIDOR THAT MAY SUPPORT SOME ISOLATED SHOWERS WITH
THE FRONTAL PASSAGE.
BY THIS EVENING BOTH THE NAM AND GFS SHOW 35 TO 40 KNOTS OF MOIST
UPSLOPE FLOW AGAINST THE TN BORDER. LIKELY POPS WILL BE CARRIED
ALONG THE TN BORDER THIS EVENING...WITH CATEGORICAL TONIGHT. SNOW
LEVELS WILL FALL TO THE VALLEY FLOORS BY LATE EVENING. THE LIMITING
FACTORS FOR SNOWFALL WILL BE THE RATHER SHALLOW DEPTH OF THE LOW
LEVEL MOISTURE...AND THE BRIEF DURATION OF THE EVENT...AS THE SYSTEM
RAPIDLY MOVES EAST AND HEIGHTS BEGIN TO RISE. SNOW ADVISORY CRITERIA
IS EXPECTED ALONG THE TN BORDER FROM AVERY CO TO MADISON CO...AND
ABOVE 3500 FEET FROM THE NORTHERN BLUE RIDGE TO BUNCOMBE CO TO THE
SMOKIES. WINDS WILL BE AT OR NEAR ADVISORY CRITERIA OVER THE NC
MOUNTAINS AND RABUN CO GA...ALTHOUGH THE SMOKIES ARE A WEAK CASE AT
THIS TIME. WITH SEVERAL MOUNTAIN PASSES BLOCKED BY PREVIOUS
LANDSLIDES...AND HOLIDAY TRAVEL THROUGH THE MOUNTAINS IN
JEOPARDY...WILL ADVISE FOR IMPACT AS WELL AS CRITERIA.
TEMPERATURES WILL BE NEAR NORMAL AHEAD OF THE FRONT TODAY...FALLING
TO FIVE DEGREES OR SO BELOW NORMAL TONIGHT.
SHORT TERM /FRIDAY THROUGH SUNDAY/
AS OF 325 AM THU...DEEP STRONG NW FLOW REMAINS OVER THE AREA FRI
MORNING. WITH CONTINUED LOW LEVEL MOISTURE AND CAA DURING THE
MORNING...HAVE LIKELY POP WITH ADDITIONAL LIGHT ACCUM THRU MID
MORNING. MOISTURE AND CAA BEGIN TO TAPER OFF DURING THE LATE
MORNING...SO TAPER POPS BACK TO GOOD CHC THEN SLIGHT CHC FOR THE
AFTERNOON. THIS ADDITIONAL ACCUM STILL IN ADV CRITERIA...MEANS ADV
WILL RUN UNTIL NOON. WINDS AND GUSTS WILL REMAIN OVER ADV CRITERIA
THROUGH NOON...THEN BEGIN TO TAPER OFF DURING THE AFTERNOON. THE ADV
WILL CONTINUE THRU 6 PM. DRY AND BREEZY CONDITIONS EXPECTED OUTSIDE
OF THE MTNS. HIGHS BELOW NORMAL.
WINDS TAPER OFF DURING THE EVENING...HOWEVER IT IS POSSIBLE THAT
ADV LEVEL GUSTS COULD CONTINUE THRU THE EVENING OVER THE HIGHER
ELEVATIONS. OTHERWISE...DRY FCST WITH CLEARING SKIES. LOWS WELL
BELOW NORMAL. RIDGING SFC AND ALOFT BUILD INTO THE AREA SATURDAY.
THICKNESSES RISE IN RESPONSE. HOWEVER...HAVE TRENDED TOWARD THE
COOLER GUIDANCE AS TENDS TO WARM TOO QUICKLY IN THESE SITUATIONS.
THIS STILL GIVES US HIGHS NEAR NORMAL.
RIDGING REMAINS OVER THE AREA SAT NITE WITH NEARLY CLEAR SKIES.
HOWEVER...LEE TROF MAY KEEP WINDS ABOVE CALM. THEREFORE...NOT THE
BEST RADIATIONAL CONDITIONS. USED GUIDANCE BLEND WITH TEMPS NEAR TO A
LITTLE BELOW NORMAL. ZONAL FLOW DEVELOPS SUNDAY WITH SFC RIDGE AXIS
MOVING OFF THE COAST. EXPECT AN INCREASE IN HIGH LEVEL MOISTURE
DURING THE DAY...BUT STILL MOSTLY SUNNY. LIGHT SWLY FLOW AND
INCREASING THICKNESSES WILL PUSH TEMPS HIGHER AND ABOVE NORMAL.
LONG TERM /SUNDAY NIGHT THROUGH WEDNESDAY/
AS OF 230 AM THURSDAY...THE MEDIUM RANGE FCST PICKS UP AT 00Z ON
MONDAY WITH A SPLIT FLOW PATTERN OVER THE CONUS AND ANOTHER COLD
FRONT APPROACHING THE CWFA. THAT FRONTAL SYSTEM IS EXPECTED TO
QUICKLY TRAVERSE THE AREA AND MOVE OFFSHORE AS HIGH PRESSURE BRIEFLY
BUILDS OVER THE REGION ON TUES. THE MODELS THEN DEVELOP ANOTHER SFC
LOW OVER THE NORTHERN GULF OF MEXICO AND MOVE THE SYSTEM OVER THE
AREA. I CONTINUED TO LEAN TOWARDS THE HPC/ECMWF SOLUTION WHICH IS
WETTER THROUGH MOST OF THE MEDIUM RANGE. THE GFS HAS A MORE PROGRESSIVE
NRN STREAM TROUGH AND MORE SHORTWAVE RIDGING BETWEEN IT AND THE SRN
STREAM CUT OFF LOW. THIS RESULTS IN A DRIER PATTERN AND A FASTER
MOVING INITIAL AREA OF PCPN. I KEPT BEST POPS ON MON AND MON NIGHT
INTO EARLY TUES. AT PRESENT ALL THE PCPN SHOULD BE LIQUID EXCEPT FOR
THE POSSIBILITY FOR SOME FROZEN PRECIP AT THE VERY END OF THE PERIOD
WHEN TEMPS FALL BELOW FREEZING IN THE HIGHER ELEVATIONS OF THE NC
MOUNTAINS.
AVIATION /09Z THURSDAY THROUGH MONDAY/
AT KCLT...KCLT HAS FALLEN TO LIFR IN FOG...AND THOSE CONDITIONS
SHOULD PERSIST UNTIL HEATING AND MIXING AFTER SUNRISE. WINDS WILL
COME UP FROM THE NORTHEAST THIS MORNING BEHIND A WEAK FRONT...THAT
HAS JUST ENOUGH MOISTURE FOR SCATTERED LOW CLOUDS..AND PERHAPS SOME
SHOWERS TO THE NORTH OF THE AIRFIELD. BY EVENING NORTHWEST WINDS
BECOME QUITE GUSTY BEHIND A SECONDARY FRONT.
ELSEWHERE...LIFR CONDITIONS WILL PERSIST AT KHKY...WITH MVFR TO IFR
FOG DEVELOPING AT THE OTHER SITES BY DAWN. CONDITIONS IMPROVE
AFTER DAWN WITH HEATING AND MIXING...AS WINDS COME UP FROM THE WEST
NORTHWEST. A FEW LOW CLOUDS WILL ACCOMPANY A WEAK FRONT AT MIDDAY.
BY EVENING A STRINGER BUT DRIER SECONDARY FRONT WILL CAUSE NORTHWEST
WINDS TO INCREASE AND BECOME GUSTY.
OUTLOOK...BREEZY NORTHWEST WINDS WILL CONTINUE LATE THURSDAY NIGHT
AND FRIDAY. THERE COULD BE BRIEF PERIODS OF RESTRICTIONS IN SHOWERS
AT KAVL...MAINLY EARLY FRIDAY MORNING. OTHERWISE...VFR THROUGH
SUNDAY. RESTRICTIONS ASSOCIATED WITH PRECIPITATION COULD OCCUR ON
MONDAY.
GSP WATCHES/WARNINGS/ADVISORIES
GA...WIND ADVISORY FROM 6 PM THIS EVENING TO 6 PM EST FRIDAY FOR
GAZ010.
NC...DENSE FOG ADVISORY UNTIL 9 AM EST THIS MORNING FOR NCZ035>037-
056-057-068>072-082-502-504-506-508-510.
WINTER WEATHER ADVISORY FROM 6 PM THIS EVENING TO NOON EST
FRIDAY FOR NCZ033-048>053-058-059-501-503-505.
WIND ADVISORY FROM 6 PM THIS EVENING TO 6 PM EST FRIDAY FOR
NCZ033-048>053-058-059-062>065-501-503-505-507-509.
SC...DENSE FOG ADVISORY UNTIL 9 AM EST THIS MORNING FOR SCZ006>009-
012>014.
SYNOPSIS...JAT
NEAR TERM...JAT
SHORT TERM...RWH
LONG TERM...JPT
AVIATION...JAT
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