FXUS62 KGSP 030236
AFDGSP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
936 PM EST WED DEC 2 2009
.SYNOPSIS...
A LOW PRESSURE SYSTEM WILL MOVE FROM THE OHIO VALLEY TONIGHT TO NEW
ENGLAND ON THURSDAY AS HIGH PRESSURE WITH DRIER AIR MOVES INTO OUR
REGION. A STRONG UPPER LEVEL SYSTEM AFFECTS THE SOUTHEAST ON
SATURDAY. BEHIND THIS SYSTEM...HIGH PRESSURE WILL RETURN TO THE
FORECAST AREA AND REMAIN IN PLACE THROUGH EARLY NEXT WEEK.
&&
.NEAR TERM /THROUGH THURSDAY/...
DEEPER MOISTURE AND HEAVIER RAIN HAS MOVED E OF AREA THIS EVE. A
NARROW BAND OF SHWRS ASSOC WITH THE SFC FRONT WILL MOVE ACROSS THE
CWA FROM THE W BUT SIGNIFICANT RAINFALL IS NOT EXPECTED WITH THIS
FEATURE. SINCE MOST AREAS WITH ELEVATED WATER LEVELS CONTINUE TO
DECREASE AND ADDITIONAL FLASH FLOODING IS NOT EXPECTED...WILL CANCEL
FLASH FLOOD WATCH WITH THIS UPDATE. 40-50KT OF WIND STILL SHOWS UP
AT 5K FT ON 88D WIND PROFILE AND 850MB MODEL OUTPUT SO WILL LEAVE
WIND ADVSRY UP FOR MAINLY HIGHER MTN ELEVS OVERNIGHT. TWEAKED
TEMP/DP FCST WITH LATEST GUIDANCE AND TRENDS. UPDATED PRODUCTS ARE
GENERATING NOW.
PREVIOUS DISCUSSION...WIDESPREAD MODERATE TO HEAVY RAIN WILL
CONTINUE THRU THE REST OF THE AFTERNOON. THE END IS IN SIGHT HOWEVER
AS THE BACK EDGE OF THE PRECIP IS MOVING INTO CENTRAL GA ATTM. THAT
SAID...WITH THE ONGOING FLOODING AND SEVERAL HOURS OF HEAVY RAIN TO
GO...WILL KEEP FFA AS IS SINCE ADDITIONAL FLOODING IS LIKELY. TRIPLE
POINT LOW IS MOVING ALONG A BOUNDARY THAT HAS FORMED NEAR THE SRN
CWFA BORDER. SPC HAS PLACED A TORNADO WATCH THERE...SO WE WILL HAVE
TO WATCH THIS AREA CLOSELY FOR POTENTIAL SEVERE STORMS THIS
AFTERNOON AND THE SOUTHEASTERN CWFA BORDER THIS EVENING. THE STRONG
LOW LEVEL WINDS WILL CONTINUE ACROSS THE AREA OVERNIGHT.
HOWEVER...THEY WILL CHANGE TO A SOUTHWESTERLY DIRECTION AND SHOULD
HAVE LESS IMPACT ON THE SC/GA MTNS AFTER MIDNIGHT. WILL EXTEND THE
WIND ADV OVER THE NC MTNS ALL NIGHT...BUT KEEP THE SC/GA MTNS ENDING
AT MIDNIGHT. PRECIP ENDS FROM SOUTHWEST TO NORTHEAST THIS EVENING AS
COLD FRONT MOVES THRU THE AREA. CLEARING WILL OCCUR OUTSIDE OF THE
MTNS AFTER MIDNIGHT AS WELL. COPIOUS LOW LEVEL MOISTURE REMAINS OVER
THE MTNS OVERNIGHT. ALTHOUGH THE FLOW WILL NOT BE NWLY THERE WILL BE
SOME WEAK COLD ADVECTION AND SYNOPTIC SCALE LIFT AS A SHORT WAVE AND
UPPER JET MOVE THRU. THEREFORE...WILL HAVE SCT TO ISOLATED SHOWERS
AFTER MIDNIGHT. ALTHOUGH THERE IS SOME CAA OVERNIGHT...TEMPS AND
PARTIAL THICKNESSES DO NOT SUPPORT ANY P-TYPE OTHER THAN RAIN.
WEATHER WILL BE MUCH CALMER WEDNESDAY WITH DEEP SWLY FLOW IN THE
WAKE OF THE UPPER LOW THAT CAUSED THE WEATHER TUESDAY. THERE WILL BE
SOME LINGERING MOISTURE OVER THE MTNS AND BREEZY TO WINDY NWLY FLOW
IN THE GRADIENT BETWEEN THE DEPARTING SFC LOW AND HIGH PRESSURE OVER
THE MID WEST. THIS WILL KEEP SCT TO ISOLATED SHOWERS OVER THE NC
MTNS DURING THE MORNING THEN DIMINISHING DURING THE AFTERNOON. TEMPS
AND PARTIAL THICKNESSES FINALLY FALL ENUF TO ALLOW A LITTLE SNOW OR
SLEET TO MIX IN OVER THE HIGHEST ELEVATIONS OF THE SMOKIES. NO
ACCUMULATIONS ARE EXPECTED. OUTSIDE OF THE MTNS CLEARING SKIES AND
DIMINISHING WINDS ARE EXPECTED. HIGHS ABOVE NORMAL OUTSIDE OF THE
MTNS AND BELOW NORMAL OVER THE MTNS.
&&
.SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY NIGHT/...
AS OF 230 PM EST WEDNESDAY...AN UPPER TROUGH WILL EXTEND FROM HUDSON
BAY TO TX THURSDAY NIGHT...WITH SOUTHWEST FLOW ALOFT FROM THE GULF
TO NEW ENGLAND. A STRONG SHORTWAVE WILL ROUND THE BASE OF THE TROUGH
ON FRIDAY...THEN WILL MOVE FROM THE GULF TO THE APPALACHIANS ON
SATURDAY.
HIGH PRESSURE WILL BUILD EAST ACROSS THE SOUTHERN APPALACHIANS ON
THURSDAY NIGHT AND FRIDAY. THE MODELS SHOW MODEST LOW LEVEL MOISTURE
LINGERING ALONG THE TN BORDER BEHIND A DEPARTING FRONT...WHILE UPPER
LEVEL MOISTURE INCREASES. A SURFACE LOW WILL MOVE ALONG THIS FRONT
IN THE GULF FRIDAY NIGHT WHILE ANOTHER WAVE DEVELOPS OFF THE
CAROLINA COAST. LOW LEVEL MOISTURE WILL INCREASE FROM THE EAST
FRIDAY NIGHT AND SATURDAY...WITH A WEAK LOW LEVEL UPSLOPE FLOW INTO
THE BLUE RIDGE ESCARPMENT. THE GFS SHOWS WEAK ISENTROPIC UPGLIDE
FRIDAY EVENING ..WITH DOWNGLIDE AND DECREASING MOISTURE BY SATURDAY
AFTERNOON. PARTIAL THICKNESS AND SURFACE TEMPERATURES ARE HIGH
ENOUGH THAT AREAS EAST OF THE MOUNTAINS WILL SEE LIQUID
PRECIPITATION FRIDAY NIGHT AND SATURDAY. PARTIAL THICKNESS FALLS
BELOW CRITICAL THRESHOLDS IN THE MOUNTAINS...STAYING THERE THROUGH
SATURDAY...AND WHERE SNOW WILL BE CARRIED ABOVE 2000 FEET...WITH A
MIX FROM 1500 TO 2000 FEET...BEFORE DRYING OCCURS SATURDAY EVENING.
TEMPERATURES WILL BE A BIT BELOW NORMAL ON FRIDAY...THEN WILL
EXHIBIT A LOW DIURNAL RANGE SATURDAY WITH CLOUDS AND PRECIPITATION.
&&
.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
AS OF 230 PM EST WEDNESDAY...THE GFS AND ECMWF ARE IN REASONABLE
AGREEMENT WITH THE LARGE SCALE PATTERN. A LOW AMPLITUDE UPPER TROUGH
WILL BE OVER THE WEST SUNDAY...WITH A FLAT RIDGE OVER THE EAST. BY
MONDAY ZONAL FLOW EXISTS ACROSS THE SOUTHERN TIER OF STATES. ON
TUESDAY THE WESTERN TROUGH AMPLIFIES...WITH SOUTHWEST FLOW OVER THE
SOUTHEAST. THE MODELS DIVERGE LATE TUESDAY AS THE ECMWF TROUGH
PROGRESSES INTO MS VALLEY. HPC NOTED VARIATIONS WITH SHORTWAVE
SYSTEMS...LEADING TO A PREFERRED BLEND OF ECMWF AND GFS AND THEIR
ENSEMBLE MEANS.
SUNDAY WILL FEATURE DRY HIGH PRESSURE OVER THE CENTRAL APPALACHIANS.
WHICH REACHES THE EASTERN COAST MONDAY...REMAINING THERE ON
TUESDAY. WHILE THE GFS WOULD SUGGEST SOME MOIST UPGLIDE AROUND THE
PERIPHERY OF THIS RIDGE...IT KEEPS OUR AREA DRY. BY WEDNESDAY A
SURFACE WAVE REACHES THE LOWER OH VALLEY...WITH A WARM FRONT MOVING
UP THE EAST COAST. MOIST GULF FLOW LIFTING OVER THIS BOUNDARY WILL
SUPPORT STRATIFORM RAIN TUESDAY NIGHT. AS THE WARM FRONT LIFTS NORTH
WEDNESDAY THE WARM SECTOR ARRIVES...SHOWERS AND PERHAPS ISOLATED
THUNDERSTORMS WILL PRECEDE A COLD FRONT APPROACHING FROM THE WEST.
TEMPERATURES NEAR MID WINTER CLIMATOLOGY PERSIST SUNDAY THROUGH
TUESDAY WITH COOL HIGH PRESSURE TO THE NORTH. CLOUD COVER WILL
MODERATE LOW TEMPERATURES TUESDAY NIGHT. MAXIMUM TEMPERATURES
WEDNESDAY PRESENT A CHALLENGE...AS THE TIMING OF WARM FRONTAL
PASSAGE WILL DICTATE HOW MUCH WARMING OCCURS BEFORE THE COLD FRONT
ARRIVES FROM THE WEST.
&&
.AVIATION /03Z THURSDAY THROUGH MONDAY/...
AT KCLT AND ELSEWHERE...VSBY WILL CONT TO IMPROVE AS SYSTEM MOVES E
WITH INCRSNG BREAKS IN IFR CIGS BECOMING VFR MID-LATE EVE.
HOWEVER...KEPT TEMPO IFR CIGS IN SHWRS THIS EVE. WINDS WILL BE
SQUIRRELY UNTIL FROPA AFTER MIDNIGHT...THEN S-SW OVERNIGHT. WINDS
WILL SWING NW AT KAVL AND NW FLOW OVER MTNS WILL BRING CIGS DOWN
AGAIN KAVL WITH GRADUAL IMROVEMENT THU. ELSEWHERE EXPECT W-SW WINDS
THU.
OUTLOOK...VFR EXPECTED THU NIGHT-FRI...BUT BRIEF MVFR POSSIBLE AT
KAVL AROUND SUNRISE. ANOTHER PERIOD OF MVFR CONDITIONS PCBL SAT AS
AN UPPER DISTURBANCE MOVES THROUGH...WHICH COULD RESULT IN SOME
LIGHT SNOW OVER THE MTNS. HI PRES BUILDS OVER AREA SUN-TUE.
&&
.GSP WATCHES/WARNINGS/ADVISORIES...
GA...WIND ADVISORY UNTIL MIDNIGHT EST TONIGHT FOR GAZ010-017.
NC...WIND ADVISORY UNTIL 6 AM EST THURSDAY FOR NCZ033-048>053-058-
059-062>065-501-503-505-507-509.
SC...WIND ADVISORY UNTIL MIDNIGHT EST TONIGHT FOR SCZ001>003.
&&
$$
SYNOPSIS...DEO
NEAR TERM...RB/RWH
SHORT TERM...JAT
LONG TERM...JAT
AVIATION...RB
