FXUS62 KGSP 260532
AFDGSP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
1232 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 TODAY/...
SUBTLE COLD FRONT ANALYZED ACRS THE WESTERN CWFA THIS EVENING WILL
WEAKEN FURTHER OVERNIGHT AS IT SAGS SE OF THE CWFA THURSDAY MORNING.
WEAK SOUTHERLY BLYR FLOW WILL VEER TO NORTHWEST ACCORDINGLY IN THE
WAKE OF THE FRONT. THE 00 UTC NAM CONTINUES TO MAXIMIZE BLYR RH
ROUGHLY ALONG AND EAST OF A KHKY-KGSP LINE INTO THE LATE NIGHT
HOURS...WHERE AREAS OF FOG AND PERHAPS SOME STRATUS REMAINS
PROBABLE. FOG PRODUCT IR SATELLITE IMAGERY DENOTES STRATOCU
FIELD DEVELOPING SE AND WILL SPREAD INTO THE WESTERN NC MTNS
DURING THE PRE-DAWN HOURS. AWAY FROM THE TENNESSEE BORDER
COUNTIES...AREAS OF VALLEY FOG ARE EXPECTED AS WELL. ESSENTIALLY
JUST TWEAKS EXPECTED TO MADE TO GOING SEASONABLE MIN TEMP FCST.
THANKSGIVING DAY...S/WV TO ADVECT ACRS THE CENTRAL-SOUTHERN
APPALACHIANS DURING THE AFTN HOURS. AN ASSOCIATED COLD FRONT ARRIVES
JUST AHEAD OF THE UPPER TROF...BRINGING WITH IT SOME LLVL MOISTURE.
H85 WINDS REMAIN RELATIVELY BACKED THRU THE AFTN (270-300 DEG)...AND
ONLY 15-20 KTS. SO THERE WILL BE LITTLE UPSLOPE FORCED SHOWERS. A
SLGT CHC POP FOR THE NRN MTNS STILL LOOKS GOOD. ANY SNOW MIXING IN
WITH THE RAIN IS NOT EXPECTED TO AMOUNT TO ANY SIGNIFICANT
ACCUMULATION THRU 6 PM. TEMPS WILL BE MAINLY IN THE 40S IN THE HIGH
ELEVATIONS...50S IN THE VALLEYS...AND LOWER 60S ACROSS THE PIEDMONT.
&&
.SHORT TERM /TONIGHT THROUGH SATURDAY/...
AS OF 130 PM WED...MAIN WEATHER IMPACT IN THE SHORT TERM WILL BE A
RATHER QUICK HITTING NW FLOW SNOW EVENT FOR THE NC MOUNTAINS THU
NIGHT INTO EARLY FRI. 12Z MODEL RUNS OFFER NO SURPRISES...AS A DEEP
UPPER LOW IS FORECAST TO MOVE THROUGH THE SOUTHERN GREAT LAKES THU
EVENING/NIGHT...WITH THE UPPER TROUGH AXIS MOVING ACROSS THE NC
MOUNTAINS IN THE 00-03Z FRI TIMEFRAME. BEST DPVA IS A LITTLE AHEAD OF
THE DEEPER MOISTURE AND BEST UPSLOPE...BUT NEVERTHELESS THERE SHOULD
BE SUFFICIENT SUPPORT TO GENERATE 1-2 INCHES OF SNOW ACROSS THE WEST
FACING SLOPES NEAR THE TENNESSEE LINE THU NIGHT INTO EARLY FRI. SNOW
LEVELS WILL QUICKLY DROP THU EVENING FROM AROUND 3500FT TO THE
VALLEY FLOORS BY MIDNIGHT. WITH GOOD COLD ADVECTION AND TIGHTENING
PRESSURE GRADIENT...EXPECT GUSTY NW WINDS WILL ALSO DEVELOP. GUSTS
TO 30-40 MPH ARE A GOOD BET IN THE MOUNTAINS ABOVE 3500FT AND 20-30
MPH BELOW. EXPECT THAT THE OVERNIGHT CREW WILL HOIST A WINTER
WEATHER ADVISORY FOR THU NIGHT FOR THE COUNTIES ADJACENT TO THE TN
LINE TO ADDRESS THE SNOW AND WIND SITUATION. DEPTH OF MOISTURE QUICKLY
ERODES BY FRI AFTERNOON...SO EXPECT THAT SNOW SHOWERS WILL DIMINISH
TO FLURRIES BY EARLY FRI AFTERNOON IN THE UPSLOPE AREAS AND END
CERTAINLY BY LATE AFTERNOON. OUTSIDE OF THE MOUNTAINS...DOWNSLOPE
FLOW WILL PREVAIL WITH GENERALLY CLEAR CONDITIONS ALONG WITH COLDER
TEMPERATURES THU NIGHT. SOME GUSTY WINDS ON FRI WILL MAKE FOR A
CHILLY DAY. HIGH PRESSURE WILL BUILD OVER THE REGION FRI NIGHT AND
CREST OVER THE AREA ON SAT. EXPECT GENRALLY CLEAR CONDITIONS TO
PREVAIL THROUGH SAT NIGHT WITH SOME MODERATION IN TEMPERATURES FOR
SAT. USED A MOS BLEND FOR TEMPS THROUGH FRI NIGHT. HOWEVER...I
UNDERCUT GMOS/MEX BY ABOUT A CATEGORY ON SAT PER 1000-850 THICKNESS
SCHEME. USED HPC GUIDANCE FOR SAT NIGHT TEMPS.
&&
.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
AS OF 200 PM WEDNESDAY...THE 12 UTC GFS AND LAST NIGHT/S RUN OF THE
ECMWF BOTH DEVELOP A SPLIT FLOW PATTERN OVER THE CONUS EARLY NEXT
WEEK. HPC FAVORS THE EC SOLUTION WHICH IS WETTER OVER OUR AREA
THROUGH MUCH OF THE EXTENDED. THE EC HAS MORE PHASING BETWEEN THE
STREAMS AS IT SLOWLY MOVES THE POSITIVELY TILTED TROUGH INTO THE ERN
US. THIS RESULTS IN LARGE BAND OF PCPN THAT CROSSES THE REGION MON
AND MON NGHT. THE GFS HAS A MORE PROGRESSIVE NRN STREAM TROUGH AND
CONSIDERABLY 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. RIGHT NOW ALL THE PCPN LOOKS TO BE LIQUID
DURING THIS TIME PERIOD.
THE TRAILING SRN STREAM LOW WILL THEN EJECT QUICKLY TO THE NE IN
RESPONSE TO A BOAT-LOAD OF ENERGY FALLING INTO THE NRN TIER OF THE
US LATER TUE INTO WED. AS THIS SRN STREAM LOW LIFTS TO THE
NORTH...PCPN SHOULD REDEVELOP AHEAD OF IT. THE RETREATING NRN STREAM
TROUGH WILL BRING HIGH PRESSURE INTO THE REGION AHEAD OF THE
LOW...AND THIS LOOKS LIKE A GOOD COLD AIR DAMMING SETUP.
ATTM...WHILE THERE SHOULD BE A PLENTY OF PCPN...THE PREDOMINATE
P-TYPE STILL LOOKS TO BE LIQUID. IT/S POSSIBLE...HOWEVER...THAT A
STRONGER RIDGE MAY RESULT OF PARTIAL THICKNESSES LOW ENOUGH FOR SOME
TYPE OF MIX OVER PARTS OF THE NC FOOTHILLS AND MTNS. IT/S A LONG
WAYS OFF...BUT IT/S CERTAINLY SOMETHING TO KEEP AN EYE ON.
&&
.AVIATION /06Z 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...NONE.
NC...NONE.
SC...NONE.
&&
$$
SYNOPSIS...JAT
NEAR TERM...ARK/CSH
SHORT TERM...LG
LONG TERM...MCAVOY
AVIATION...JAT
