FXUS62 KCHS 270454
AFDCHS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
1154 PM EST THU NOV 26 2009
.SYNOPSIS...
A DRY COLD FRONT WILL MOVE THROUGH THE AREA TONIGHT WITH HIGH
PRESSURE THEN BUILDING INTO THE REGION AND REMAINING IN CONTROL
THROUGH MONDAY. A COLD FRONT WILL DROP THROUGH THE AREA MONDAY
NIGHT AND TUESDAY...THEN A SERIES OF GULF LOW PRESSURE SYSTEMS
WILL AFFECT THE SOUTHEAST UNITED STATES WEDNESDAY AND THURSDAY.
&&
.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
A SHARP UPPER TROUGH WILL PUSH THROUGH THE REGION THIS EVENING...
HELPING STRONG COLD AIR ADVECTION TO COMMENCE. AREA OBS HAVE
ALREADY DROPPED TO AROUND 50 AND WILL CONTINUE A STEADILY DOWNFALL
THROUGH THE REMAINDER OF THE OVERNIGHT HOURS. ALTHOUGH BOUNDARY
LAYER WINDS LOOK TOO STRONG TO ALLOW THE ATMOSPHERE TO DECOUPLE...
A RATHER CHILLY NIGHT IS ON TAP WITH LOWS RANGING FROM THE MID 30S
WELL INLAND TO THE LOWER 40S AT THE COAST. WITH WINDS NOT DROPPING
NEAR CALM NOR WITH ANY APPRECIABLE MOISTURE NEAR THE SFC...FROST
DEVELOPMENT IS HIGHLY UNLIKELY SO WILL NOT HAVE ITS MENTION IN THE
FORECAST.
LAKE WINDS...A CLASSIC LAKE WIND EVENT IS DEVELOPING ACROSS LAKE
MOULTRIE TONIGHT AS MODEST COLD AIR ADVECTION INTERACTS WITH THE
RELATIVELY WARMER OPEN LAKE WATERS. MODIFIED FORECAST SOUNDINGS
YIELD AS MUCH AS 25-30 KT WITHIN THE MIXED LAYER...WHICH SHOULD
YIELD SURFACE WINDS OF 20-25 KT. THIS IS BEING CONFIRMED WITH
RECENT PINEVILLE OBS SHOWING 20-25 KT WINDS. WILL CONTINUE THE
LAKE WIND ADVISORY INTO FRIDAY MORNING. EXPECT WAVES OF 1-2 FT
WITH THE HIGHEST WAVES OCCURRING OVER THE CENTRAL AND EASTERN
PORTIONS OF THE LAKE.
&&
.SHORT TERM /6 AM FRIDAY MORNING THROUGH FRIDAY NIGHT/...
HIGH PRESSURE WILL SLIDE EAST TOWARD THE AREA THIS PERIOD
PROVIDING UNSEASONABLY COOL TEMPERATURES. ALTHOUGH COLD ADVECTION
WILL BECOME MORE NEUTRAL ON FRIDAY AND PLENTY OF SUNSHINE IS
EXPECTED...THINK HIGHS WILL STRUGGLE TO REACH 60 DEGREES MOST
LOCALES. UNDER CLEAR SKIES...TEMPERATURES WILL DROP QUICKLY IN THE
EVENING...BUT THERE IS SOME UNCERTAINTY AS TO HOW LOW THEY WILL GO
DUE TO THE MODELS SHOWING AROUND 10 KT OF WIND IN THE BOUNDARY
LAYER. WILL STILL INDICATE SOME FREEZING TEMPERATURES WELL INLAND
FROM AROUND RIDGEVILLE TO ALLENDALE TO STATESBORO TO MILLEN BUT
AFTER COORDINATION WITH SURROUNDING OFFICES...WILL HOLD OFF ON A
FREEZE WATCH FOR NOW. WILL MAINTAIN THE MENTION OF WIDESPREAD
FROST AWAY FROM THE COAST BUT DUE TO THE UNCERTAINTY IN THE WINDS
AND AFTER COORDINATION WITH NEARBY OFFICES...WILL WAIT ANOTHER
FORECAST CYCLE.
&&
.LONG TERM /SATURDAY THROUGH THURSDAY/...
A RELATIVELY ZONAL FLOW WILL PERSIST SATURDAY INTO MONDAY WITH A
LARGE BUBBLE OF HIGH PRESSURE AT THE SURFACE. AS THE LOW-LEVEL FLOW
BACKS THROUGH THE PERIOD...A QUICK WARM-UP WILL OCCUR WITH MOSTLY
CLEAR SKIES. WE COULD HAVE SOME FROST CONCERNS ACROSS INLAND
LOCATIONS SUNDAY MORNING WHERE WE ARE STILL FORECASTING SOME MID 30S
FOR LOWS WITH LIGHT WINDS. HIGHS WILL BE IN THE MIDDLE 60S SATURDAY
WITH 70S FORECAST SUNDAY AND MONDAY.
A CHANNELED NORTHERN STREAM VORT MAX IS PROGGED TO TREK FROM THE
OHIO VALLEY INTO THE MID-ATLANTIC...DRAGGING A COLD FRONT INTO THE
CAROLINAS MONDAY NIGHT INTO TUESDAY. GUIDANCE HAS SLOWED THIS
FEATURE DOWN BY ABOUT 12 HRS FROM THE PREVIOUS RUNS...THUS WE HAD TO
REMOVE PRECIP CHANCES FROM MONDAY. THE UPPER PATTERN IS SUCH THAT
FURTHER DELAYS IN THE FRONTAL PASSAGE WOULD NOT BE SURPRISING.
TUESDAY THROUGH THURSDAY LOOK QUITE UNSETTLED AS A CLOSED UPPER LOW
LIFTS OUT OF WESTERN TX AND MOVES THROUGH THE SOUTHERN STATES. WITH
A FRONTAL BOUNDARY LIKELY ALONG THE SC/GA COAST ON TUESDAY AND A
SERIES OF SURFACE LOWS FORMING IN THE GULF OR OFF THE GA COAST AND
MOVING NORTHEAST WED AND THU...WE MAINTAINED CHANCE POPS AND CLOUDY
SKIES. TEMPS WILL RETURN TO NEAR NORMAL WITH HIGHS IN THE LOWER 60S
AND LOWS IN THE 40S.
&&
.AVIATION /06Z FRIDAY THROUGH TUESDAY/...
VFR CONDITIONS WILL PREVAIL AT KCHS AND KSAV THROUGH FRIDAY
EVENING. WINDS MAY GUST AS HIGH AS 20 KT AFTER SUNRISE.
EXTENDED AVIATION OUTLOOK...VFR CONDITIONS THROUGH MONDAY. MVFR OR
LOWER CEILINGS AND/OR VISIBILITIES POSSIBLE MONDAY NIGHT INTO
TUESDAY WITH A COLD FRONT.
&&
.MARINE...
HAVE UPGRADED THE SMALL CRAFT ADVISORY FOR THE GEORGIA OFFSHORE
LEG TO A GALE WARNING THROUGH 6 AM FRIDAY. WINDS HAVE BEEN GUSTING
OVER GALE FORCE AT 41004 OVER THE PAST SEVERAL HOURS WITH A PEAK
GUST OF 39 KNOTS MEASURED AT 04Z. 41008 IS ALSO NOW APPROACHING
GUSTS TO GALE FORCE. CURRENT DATA SUPPORTS UPGRADING TO GALES
FOR AMZ374 ATTM AND RAISING SEAS SLIGHTLY. COULD SEE WINDS GUST AS
HIGH AS 40 KT AT TIMES...MAINLY BEYOND 40 NM WHERE THE CORRIDOR OF
WARMEST SEA SURFACE TEMPERATURES ARE FOUND. THANKS OPC FOR THE
COLLABORATION. NO MAJOR CHANGES WERE MADE FOR THE NEARSHORE WATERS
INCLUDING THE CHARLESTON HARBOR WHERE SMALL CRAFT ADVISORIES
REMAIN IN EFFECT.
FRIDAY THROUGH FRIDAY NIGHT...THE PRESSURE GRADIENT AND COLD AIR
ADVECTION WILL WEAKEN FRIDAY ALLOWING WINDS TO WEAKEN
ACCORDINGLY. HOWEVER...THERE COULD BE ANOTHER SURGE FRIDAY NIGHT.
WILL MAINTAIN THE SMALL CRAFT ADVISORIES FOR THE NEARSHORE WATERS
AND CHS HARBOR THROUGH FRIDAY MORNING AND FOR THE WATERS BEYOND 20
NM THROUGH FRIDAY NIGHT.
SATURDAY THROUGH TUESDAY...QUIET MARINE CONDITIONS WILL PREVAIL
SATURDAY THROUGH MONDAY WITH SURFACE HIGH PRESSURE IN CONTROL.
MONDAY NIGHT OR TUESDAY AND BEYOND LOOK CONVOLUTED AS A FRONT
DROPS INTO THE WATERS AND COASTAL LOW PRESSURE DEVELOPS. MARINE
FLAGS WILL PROBABLY BE REQUIRED AT SOME POINT NEXT WEEK.
&&
.CHS WATCHES/WARNINGS/ADVISORIES...
GA...NONE.
SC...LAKE WIND ADVISORY UNTIL 11 AM EST FRIDAY FOR SCZ045.
MARINE...SMALL CRAFT ADVISORY UNTIL 11 AM EST FRIDAY FOR AMZ330-350-352-
354.
GALE WARNING UNTIL 6 AM EST FRIDAY FOR AMZ374.
&&
$$
