FXUS62 KGSP 052334
AFDGSP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
634 PM EST SAT DEC 5 2009
.SYNOPSIS...
HIGH PRESSURE WILL BUILD IN ACROSS THE FORECAST AREA THROUGH SUNDAY
MORNING...AND SLIDE OFF THE EAST COAST ON MONDAY. A FAST MOVING COLD
FRONT WILL CROSS THE APPALACHIANS MONDAY NIGHT WITH ANOTHER AREA OF
HIGH PRESSURE MOVING IN BEHIND IT. A STRONG LOW WILL DEVELOP OVER
THE PLAINS LATE TUESDAY AND MOVE NORTHEAST TO THE GREAT LAKES AS AN
ASSOCIATED COLD FRONT APPROACHES THE CAROLINAS AND GEORGIA FROM THE
WEST.
&&
.NEAR TERM /THROUGH SUNDAY/...
OTHER THAN A FEW FLURRIES...SNOW HAS ENDED OVER THE NC N MTNS SO THE
WINTER STORM WARNING WAS CANCELLED. COLD TEMPS AND MCLR SKIES
OVERNIGHT WILL LEAD TO AREAS OF BLACK ICE WHERE SNOW FELL AND
PARTIALLY MELTED ON NC MTN ROADS AND WALKWAYS. THIS IS HIGHLIGHTED
IN THE HWO AND IN AN SPS.
PREVIOUS DISCUSSION...SFC LOW PRES WAS CENTERED OFF THE N CAROLINA
OUTER BANKS AT 18Z THIS AFTERNOON. WATER VAPOR IMAGERY SHOWS THE
SHARP UPPER SHORTWAVE MOVING NE OVER THE NRN NC MOUNTAINS THIS AFTN.
THE PRECIPITATION SHIELD ASSOCIATED WITH THIS FEATURE HAS LARGELY
MOVED NORTHEAST OF THE FORECAST AREA. THE ONLY RESIDUAL RADAR
RETURNS APPEAR TO BE ASSOCIATED WITH LIGHT BUT MOIST NORTHWEST
UPSLOPE FLOW NEAR THE TN LINE. HAVE THUS CANCELLED ALL WINTER
WEATHER WARNINGS AND ADVISORIES EXCEPT FOR MADISON THROUGH
AVERY...WHERE LIGHT UPSLOPE FLOW MAY PERSIST FOR A COUPLE MORE HOURS.
OTHERWISE....FLAT RIDGING ALOFT WILL DEVELOP TONIGHT THROUGH SUNDAY.
SURFACE HIGH PRESSURE WILL BUILD OVER THE FCST AREA THROUGH THE
PERIOD. LIGHT WINDS AND CLEARING SKIES LATE TONIGHT COULD ALLOW SOME
MOUNTAIN VALLEY FOG TO DEVELOP...ESPECIALLY IN LOCATIONS THAT
RECEIVED APPRECIABLE SNOWFALL TODAY. ALSO...SUBFREEZING TEMPERATURES
OVERNIGHT WILL ALLOW ANY WET OR SNOW COVERED ROADWAYS TO FREEZE UP.
ONCE ALL THE SNOW WARNINGS ARE OFF THE BOARD...A WINTER WEATHER
ADVISORY FOR BLACK ICE COULD BE NEEDED IN AFFECTED MOUNTAIN AREAS.
CHILLY THICKNESSES UNDER HIGH PRESSURE WILL KEEP SUNDAY MAX TEMPS
WELL BELOW NORMAL. INCREASING HIGH CLOUDS WILL ENCROACH DURING THE
AFTN HOURS.
&&
.SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY/...
AS OF 130 PM SATURDAY...THE SHORT TERM WILL BE UNDER
QUASI-ZONAL/FAST UPPER FLOW...WITH A NRN STREAM SHORTWAVE AND
ASSOCIATED SFC WAVE TRACKING FROM THE MIDWEST TO NEW ENGLAND BY
TUESDAY MORNING. A WEAK TRANSIENT HIGH WILL CROSS THE APPALACHIANS
TUESDAY...WHILE A DEEP SRN STREAM SYSTEM DEEPENS OVER THE FOUR
CORNERS REGION.
SUNDAY NGT THRU MONDAY NGT...THE 12Z GFS IS A TAD QUICKER AND MORE
AMPLIFIED WITH THE NRN STREAM WAVE...AND SEEMS TOO MOIST ACRS THE
CWFA MONDAY AFTN. THE 09Z SREF/00Z ECMWF/12Z GEM ALL ARE MORE IN
LINE WITH THE 12Z NAM ON A WEAKENING FRONTAL BAND OF PRECIP REACHING
THE WRN SLOPES OF THE APPALACHIANS LATE AFTN INTO MONDAY EVE. FCST
SNDGS ALL SHOW SIGNIFICANT WARM NOSE WITH THIS PRECIP...AND I HAVE
OPTED TO KEEP IT ALL RAIN TILL I END POP AROUND MIDNIGHT MONDAY NGT.
WITH SUCH DRY LOW LEVELS DEPICTED IN THE SNDGS...I DID NOT INCR POP
AND ACTUALLY CUT ALL POP EAST OF THE MTNS. TEMPS WILL BE BELOW
NORMAL SUNDAY NIGHT...REBOUNDING TO THE 40S MTNS AND LOWER 50S
ELSEWHERE MONDAY AFTN...DESPITE PLENTY OF MID LVL CLOUDINESS. TEMPS
WILL NOT DROP AS MUCH MONDAY NGT...AS CLOUDS LINGER AND WAA BEGINS
BEFORE DAYBREAK TUESDAY (MAINLY IN THE 30S).
TUESDAY...AS LOW PRES SYS BEGINS TO PROPAGATE INTO THE SRN PLAINS
STATES...ISENTROPIC LIFT INCREASES ACRS THE AREA. THE MAIN QUESTION
IS HOW QUICKLY WILL THE COLUMN MOISTEN...AS ALL GUIDANCE HAS DELAYED
THE TIMING. I TRENDED WITH THE LATEST GUIDANCE ON BRINGING IN
HIGH-END CHC POP (ALL LIQUID GIVEN FCST THICKNESSES) OVR THE SRN
THIRD OF CWFA FOR THE AFTN. TEMPS LOOK TO BE ABOUT THE SAME AS
MONDAY/S.
&&
.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
AS OF 200 PM SATURDAY...LITTLE HAS CHANGED IN REGARD TO FORECAST
THINKING DURING THE MEDIUM RANGE...AS GLOBAL MODELS REMAIN IN GOOD
AGREEMENT IN FORECASTING THE CONTINUATION OF AN ACTIVE/PROGRESSIVE
PATTERN THROUGH AT LEAST THE END OF NEXT WEEK. TIMING OF INDIVIDUAL
PRECIPITATION SYSTEMS ALSO REMAINS QUITE CONSISTENT BETWEEN THE
ECMWF AND THE GFS...ALTHOUGH MINOR DIFFERENCES IN DETAILS DO
PERSIST. THE GFS CONTINUES TO DEPICT THE MID-WEEK FRONTAL SYSTEM
EVOLVING INTO A MILLER-B SCENARIO...ALTHOUGH THE CONTINENTAL LOW
REMAINS QUITE STRONG...AND EVEN DEEPENS AFTER COASTAL CYCLOGENESIS
IS WELL UNDERWAY. MEANWHILE...THE ECMWF MAINTAINS A DOMINANT
CONTINENTAL LOW...WITH MUCH WEAKER COASTAL DEVELOPMENT. REGARDLESS
OF WHICH MODEL SOLUTION PANS OUT CLOSER TO REALITY...TUE NIGHT AND
EARLY WEDNESDAY APPEAR TO BE QUITE WET. POPS WILL BE INCREASED TO
CATEGORICAL ACROSS MUCH OF THE CWFA TUE NIGHT. WRAP-AROUND/NW
FLOW/UPSLOPE SNOW SHOWERS WILL BE POSSIBLE ACROSS THE WESTERN NC
MTNS WED NIGHT INTO EARLY THURSDAY.
AFTER BRIEF DRYING THURSDAY...THE ECMWF/GFS ARE IN GOOD AGREEMENT IN
BRINGING YET ANOTHER STORM SYSTEM TOWARD THE AREA LATE FRIDAY INTO
SATURDAY. CHANCE POPS WILL BE CARRIED DURING THIS TIME.
&&
.AVIATION /00Z SUNDAY THROUGH THURSDAY/...
KCLT AND ELSEWHERE...MCLR OVERNIGHT...EXCEPT TEMPO MVFR CIG AT KAVL
UNTIL 03Z...THEN CLEARING. AT TERMINALS WHERE MORE PRECIP FELL
EXPECT FOG...IFR KAVL 10-14Z...MVFR KHKY 10-12Z. NO RESTRICTIONS
ELSEWHERE. N WINDS WILL SLOWLY TAPER OFF KAVL...KGSP AND KGMU. LGT
WINDS ELSEWHERE...THEN NE BECMG SE AT LESS THAN 10KT ACROSS CWA DURG
DAY SUN.
OUTLOOK...DRY THRU SUN NIGHT. A WEAK COLD FRONT WILL CROSS THE AREA
MON. DRY HIGH PRESSURE EARLY TUE...THEN NEXT SYSTEM MOVES IN FROM
THE W FOR TUE NIGHT-WED.
&&
.GSP WATCHES/WARNINGS/ADVISORIES...
GA...NONE.
NC...NONE.
SC...NONE.
&&
$$
SYNOPSIS...BSH
NEAR TERM...HG/RB
SHORT TERM...ARK
LONG TERM...JDL
AVIATION...RB
