000
FXUS62 KCHS 031957
AFDCHS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
257 PM EST WED DEC 3 2008
.SYNOPSIS...
HIGH PRESSURE WILL CONTINUE INTO THURSDAY. A COLD FRONT WILL MOVE
THROUGH THE AREA LATE THU NIGHT...THEN STALL SOUTHEAST OF OUR
COAST FRIDAY AND SATURDAY AS WEAK WAVES OF LOW PRESSURE TRAVERSE
ALONG IT. A REINFORCING COLD FRONT WILL CROSS THE AREA SATURDAY
NIGHT...FOLLOWED BY HIGH PRESSURE SUNDAY AND MONDAY. A STORM
SYSTEM COULD AFFECT THE AREA NEXT TUESDAY AND WEDNESDAY.
&&
.NEAR TERM /THROUGH TONIGHT/...
SURFACE HIGH PRESSURE WILL SHIFT OFFSHORE TONIGHT WHILE A WEAK
COASTAL TROUGH OF LOW PRESSURE DEVELOPS E OF FL AND NOSES N INTO
THE GA/SC WATERS. ATLANTIC MOISTURE RETURN IS NOT EXPECTED TO BE
STRONG AND SKIES SHOULD BE CLEAR IN THE EVENING WITH TEMPERATURES
FALLING QUICKLY AFTER DUSK. THE POTENTIAL FOR HIGH CLOUDS AND EVEN
SOME LOWER CLOUDS COMING IN OFF COASTAL WATERS MAKES THE
TEMPERATURE FORECAST QUITE CHALLENGING. THE DIFFERENCE B/W THE
STATISTICAL GUIDANCE IS LARGE...BUT WE CONTINUED ON THE COLDER
SIDE OF THE GUIDANCE GIVEN STRONG RADIATIONAL EFFECTS EARLY ON.
HAVE LOWS REACHING DOWN TO AROUND 30 DEGREES WELL INLAND WITH
LOWER TO MID 40S NEAR THE COAST WHERE A LIGHT ONSHORE FLOW IS
EXPECTED.
&&
.SHORT TERM /THURSDAY THROUGH THURSDAY NIGHT/...
THURSDAY...SINCE THE DEEPER MOISTURE LOOKS TO REMAIN W OF OUR
FORECAST AREA THU...HAVE MAINTAINED A DRY FORECAST. HIGHER THICKNESS
VALUES AND S/SW FLOW SUGGEST WE CAN ATTAIN MID 60S MANY AREAS.
THURSDAY NIGHT...DEEPER MOISTURE MOVES INTO THE AREA THU NIGHT
AHEAD OF A WEAKENING SHORTWAVE TROUGH AND WITHOUT MUCH IN THE WAY
OF FORCING FOR PRECIP WE KEPT A SLIGHT CHANCE OF SHOWERS CONFINED
TO OUR INLAND ZONES AFTER MIDNIGHT. LOWS WILL BE WARMER WITH THE
CLOUDS AND WE COULD SEE SOME AREAS OF LATE NIGHT STRATUS AND
PATCHY FOG AS LIGHT SURFACE WINDS SHIFT NLY BEHIND A BACKDOOR
FRONTAL PASSAGE.
&&
.LONG TERM /FRIDAY THROUGH WEDNESDAY/...
WEAKENING SHORTWAVE ENERGY LIFTING OUT OF THE LOWER MS VALLEY WILL
PUSH A COLD FRONT INTO THE AREA ON FRIDAY AND OFF THE COAST BY EARLY
SATURDAY. VEERING FLOW ALOFT WILL NOT BE CONDUCIVE TO SIGNIFICANT
MOISTURE ADVECTION WITH THE FRONT...WHICH EXPLAINS WHY THE ECMWF AND
GFS CONTINUE TO SHOW LESS AND LESS QPF ACCOMPANYING THE FRONT.
SCATTERED SHOWERS WILL BE POSSIBLE JUST ABOUT ANYWHERE...ALTHOUGH
WESTERN AREAS STAND THE BEST CHANCE OF A RAIN SHOWER BEFORE THE
FRONT DRIES UP. WILL RANGE POPS 20S TO 30S FROM EAST TO WEST WITH A
TAPER FROM THE WEST FRI NIGHT. DRY...COOL HIGH PRESSURE WILL BUILD
IN BEHIND THE FRONT SAT THROUGH TUE WITH BELOW-NORMAL TEMPS. RAIN
CHANCES WILL INCREASE AGAIN TUE AND WED AS THE SFC HIGH SHIFTS
EAST...A COASTAL TROUGH DEVELOPS...THEN AN UPPER VORT POTENTIALLY
TRIGGERS THE DEVELOPMENT OF A LOW PRESSURE SYSTEM IN THE SOUTHEAST.
&&
.AVIATION /20Z WEDNESDAY THROUGH MONDAY/...
MAINLY VFR CONDITIONS ARE EXPECTED THROUGH 18Z/04 AT BOTH KSAV
AND KCHS. MODELS SHOW SOME SOME WEAK LOW-LEVEL ATLC MOISTURE
RETURN TONIGHT AND THERE MAY BE SCT-BKN 3-4K FT CIGS BETWEEN
08-12Z/04 AT KCHS. COULD ALSO SEE SOME PATCHY FOG WITH 5-6 SM VSBY
AT KSAV AROUND DAYBREAK BUT WITH LOW CONFIDENCE WILL LEAVE MENTION
OUT OF 18Z/03 TAFS.
EXTENDED AVIATION OUTLOOK...OCNL MVFR/IFR CIGS/VSBYS PSBL FRI
MORNING INTO SAT MORNING...OTHERWISE VFR CONDITIONS WILL PREVAIL.
&&
.MARINE...
TONIGHT...HIGH PRES WILL SLIDE E OVER THE WATERS WHILE A TROUGH OF
LOW PRES DEVELOPS S OF THE AREA AND NOSES N INTO THE GA/SC WATERS.
OVERALL...NO SIGNIFICANT IMPACTS ON THE MARINE AREA ARE EXPECTED.
THU THROUGH THU NIGHT...HIGH PRES OFFSHORE WILL REMAIN IN CONTROL
WHILE THE LOW PRES TROUGH BREAKS DOWN EARLY THU. A WEAK COLD FRONT
WILL SINK THROUGH THE AREA LATE THU NIGHT BUT THE LACK OF ANY
SIGNIFICANT PRES GRADIENT DURING THIS TIME WILL KEEP WIND SPEEDS
AOB 15 KT.
FRIDAY THROUGH MONDAY...WINDS WILL SURGE BRIEFLY FRI NIGHT AND SAT
WITH A NORTHERLY WIND SETTING UP IN COLD ADVECTION BEHIND THE
COLD FRONT. SEAS MAY BRIEFLY BUILD AS HIGH AS 5 FT ON SAT OVER
OFFSHORE WATERS ALTHOUGH NEARSHORE LEGS WILL BE LIMITED BY A SHORT
FETCH. THE NEXT CHANCE FOR SMALL CRAFT ADVISORY CONDITIONS WILL BE
LATE SATURDAY NIGHT AND SUNDAY WITH STRONG COLD ADVECTION BEHIND A
REINFORCING COLD FRONT. BEST CHANCE WILL BE THE OFFSHORE GA
WATERS...AS USUAL...WHERE WARMER WATERS WILL FAVOR BETTER LOW-
LEVEL MIXING AND LONGER FETCH WILL ALLOW SEAS TO BUILD HIGHER.
WINDS AND SEAS WILL LIKELY REMAIN ELEVATED INTO THE MIDDLE OF NEXT
WEEK IN ASSOCIATION WITH A DEVELOPING COASTAL TROUGH TUESDAY AND
POTENTIAL STORM SYSTEM WEDNESDAY.
&&
.CHS WATCHES/WARNINGS/ADVISORIES...
GA...NONE.
SC...NONE.
MARINE...NONE.
&&
$$
RJB/JRL
