FXUS62 KGSP 281526
AFDGSP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
1026 AM EST SAT NOV 28 2009
.SYNOPSIS...
HIGH PRESSURE WILL REMAIN OVER THE AREA THROUGH THE WEEKEND ALLOWING
TEMPERATURES TO REACH A FEW DEGREES ABOVE NORMAL. LATE SUNDAY... A
COLD FRONT WILL APPROACH THE CAROLINAS AND NORTHEAST GEORGIA. THIS
FRONT WILL CROSS THE AREA ON MONDAY REACHING THE COAST BY LATE IN
THE DAY. HIGH PRESSURE WILL ONCE AGAIN BUILD BACK IN BRIEFLY UNTIL A
STORM SYSTEM APPROACHES FROM THE SOUTH WEDNESDAY.
&&
.NEAR TERM /THROUGH TONIGHT/...
NOT MUCH CHANGE IS REQUIRED TO THE AFTERNOON FORECAST...AS A DRY
SURFACE RIDGE WILL MAINTAIN SUNNY SKIES...LIGHT WINDS...AND
SEASONABLY COOL TEMPS. THE ONLY CONCERN FOR THIS AFTERNOON WILL BE
FIRE WEATHER-RELATED...DUE TO POTENTIAL LOW RH. SEE FIRE WX SECTION
BELOW FOR DETAILS.
TONIGHT...DRY HIGH PRESSURE WILL REMAIN OVER THE REGION. MILD LLVL
THICKNESSES MAY YIELD AN INVERSE LAPSE RATE. THE MIN FORECAST WILL
INDICATE MID 30S IN THE VALLEYS AND U30S ON THE RIDGES...WITH NEAR
40 DEGREES EAST OF THE MTNS. OTHERWISE...EXPECTING SKY COVER TO
TRANSITION FROM CLEAR THIS EVENING TO PARTLY CLOUDY WITH CIRRUS
DURING THE PRE DAWN HOURS.
&&
.SHORT TERM /SUNDAY THROUGH TUESDAY/...
AS OF 215 AM SATURDAY...NOT MUCH IN THE NEW MODEL GUIDANCE TO
SUGGEST SIGNIFICANT CHANGES TO THE FORECAST ARRIVAL OF THE NEXT
WEATHER SYSTEM ON MONDAY. BEFORE WE GET THERE...SUNDAY STILL LOOKS
WARM WITH SW FLOW ALOFT AHEAD OF THE APPROACHING NRN STREAM WAVE.
KEPT TEMPS CLOSE TO A BLEND OF GUIDANCE. A CONSENSUS OF THE
OPERATIONAL MODELS SUGGESTS THAT PRECIP CHANCES SHOULD DEVELOP FROM
THE WEST SUNDAY NIGHT...BUT NOT UNTIL AFTER MIDNIGHT. THINK THAT
LEADING EDGE OF SHOWER ACTIVITY WILL REMAIN OVER OR W OF MOUNTAINS
BY SUNRISE ON MONDAY. THE FORCING MOVES RAPIDLY EAST THOUGH...SO
SOME ADJUSTMENT HAS BEEN MADE TO BRING THE SHOWERS ACROSS THE
PIEDMONT A BIT EARLIER THAN BEFORE. IN GENERAL...THE GUIDANCE POP
LOOKS GOOD...WITH LIKELY OVER MOST OF THE AREA WITH FROPA LATE IN
THE DAY. HIGH TEMPS ARE GOING TO DEPEND ON THE PROGRESS OF THE
FRONT. FOR NOW...THE MAV AND MET SEEM LIKE THEY BRING COLDER AIR IN
TOO FAST BEHIND THE FRONT...SO KEPT THE FORECAST CLOSER TO THE
MOSGUIDE VALUES. BUOYANCY IS EXPECTED TO BE MINIMAL...SO HAVE KEPT
THUNDER OUT OF THE FORECAST.
THE MODELS CONTINUE TO SUGGEST A QUICK EAST DEPARTURE OF THE FRONT
AND ITS MOISTURE. HAVE KEPT A CHANCE OF PRECIP FOR THE MONDAY
EVENING HOURS ONLY FOR CONTINUITY WITH THE PREVIOUS FORECAST AND
NEIGHBORS. HOWEVER...DRY AIR PUSHES IN QUICKLY LATE MONDAY NIGHT SO
HAVE KILLED OFF THE MENTIONABLE POP FOR EARLY TUESDAY MORNING.
TUESDAY SHOULD BRING A BRIEF BREAK AS WE FALL UNDER SURFACE HIGH
PRESSURE DURING THE DAY. CLOUDS WILL INCREASE AHEAD OF THE NEXT
SYSTEM LATE IN THE DAY.
&&
.LONG TERM /TUESDAY NIGHT THROUGH FRIDAY/...
AS OF 240 AM SATURDAY...THE GFS SEEMS TO BE MOVING THE LOW UP FROM
THE GULF A BIT TOO FAST ACCORDING TO GUIDANCE. TO START THE MEDIUM
RANGE AT 00Z WEDNESDAY...THE ECMWF HAS THE FRONT OF THE RAIN SHIELD
OVER SOUTHWEST ALABAMA WHILE THE GFS HAS IT OVER CENTRAL GEORGIA.
BY 12Z WED...THE GFS HAS THE PRECIP MOVING OVER MOST IF NOT ALL OF
THE FORECAST AREA WHILE THE ECMWF HAS IT ONLY OVER MUCH OF NE GA TO
NEAR GREENWOOD SC. THE ECMWF CERTAINLY HAS GREATER PRECIP AMOUNTS
CROSSING LATE WEDNESDAY AND EARLY WED NIGHT WITH CLOSE TO 2 INCHES
MAINLY OVER PIEDMONT. DO NOT WANT TO GO THAT HIGH YET. AFTER THE
SYSTEM MOVES OUT TO THE NORTHEAST...THE GFS IS MORE AGGRESSIVE IN
BRINGING THE COLD AIR IN ON BREEZY NORTHWEST WIND INTO THURSDAY
MORNING. THE ECMWF IS ALSO BREEZY AROUND THE SAME PERIOD BUT COLDER
THICKNESS VALUES HELD BACK OVER NORTHERN TN AND KY. SEEMS THE
PERIOD OF POST SYSTEM NORTHWEST FLOW SNOW OVER THE NC MOUNTAINS WILL
BE BRIEFER AND CUT THAT OFF EARLY FRIDAY. TEMPERATURES WILL BE
SLIGHTLY BELOW NORMAL MUCH OF THIS PERIOD.
&&
.AVIATION /16Z SATURDAY THROUGH WEDNESDAY/...
AT KCLT AND ELSEWHERE...DRY SFC HIGH PRESSURE WILL REMAIN
CENTERED OVER THE SOUTHEAST U.S. TODAY. A WEAK LEE TROF SHOULD
DEEPEN SLIGHTLY LATER THIS MORNING AND REMAIN INTO THE EVENING. THE
PRESSURE GRADIENT WILL RANGE FROM 2-4 MBS THROUGH THE
DAY...RESULTING IN WINDS 5 KTS OR LESS. WIND DIRECTIONS WILL LIKELY
FALL BETWEEN 240-210 DEGREES AFTER SUNRISE. TONIGHT...FEW TO SCT
CIRRUS WILL DRIFT OVER THE REGION...WINDS WILL DECREASE 1-2 KTS OR
BECOME CALM.
OUTLOOK...DRY HIGH PRESSURE WILL WEAKEN ON SUNDAY AS A COLD FRONT
APPROACHES FROM THE WEST. THE FRONT WILL REACH THE NC MTNS LATE
SUNDAY NIGHT AND MOVE EAST ACROSS THE FOOTHILLS AND PIEDMONT DURING
THE DAYTIME ON MONDAY. PERIODS OF RESTRICTIONS WILL LIKELY ACCOMPANY
THE PASSAGE OF THE FRONT. HIGH PRESSURE WILL RETURN TO THE REGION
MONDAY NIGHT AND WILL REMAIN THROUGH TUESDAY.
&&
.FIRE WEATHER...
THERE IS SOME CONCERN ABOUT THE POTENTIAL FOR RH TO DROP THROUGH THE
FLOOR THIS AFTERNOON...ESPECIALLY SINCE DEWPOINTS ARE ALREADY QUITE
LOW AS OF 15Z (TEENS MTNS/20S PIEDMONT). HOWEVER...THERE ARE SOME
HINTS THAT DEWPOINTS WILL NOT CRATER MUCH MORE THAN THEY ALREADY
HAVE...AND MAY INCREASE SLIGHTLY THIS AFTERNOON. OWING TO FAIRLY
WARM AIR ALOFT...MIXING WILL NOT BE VERY DEEP THIS AFTERNOON. EVEN
IF MIXING BECOMES DEEPER THAN ANTICIPATED...IT APPEARS THAT SLIGHTLY
MORE MOIST AIR IS POISED TO MOVE INTO THE REGION THIS AFTERNOON FROM
THE TENN VALLEY. WE WILL CONTINUE TO FORECAST MIN RH JUST SLIGHTLY
ABOVE THE CRITICAL 25 PERCENT THRESHOLD.
&&
.GSP WATCHES/WARNINGS/ADVISORIES...
GA...NONE.
NC...NONE.
SC...NONE.
&&
$$
SYNOPSIS...DEO
NEAR TERM...JDL/NED
SHORT TERM...PM
LONG TERM...DEO
AVIATION...NED
FIRE WEATHER...JDL
