814
FXUS62 KCHS 080541
AFDCHS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
1241 AM EST SUN NOV 8 2009
SYNOPSIS
HIGH PRESSURE WILL REMAIN THE DOMINANT WEATHER FEATURE THROUGH THE
WEEKEND. THE COMBINATION OF TROPICAL CYCLONE IDA...OR ITS REMNANTS...
LIFTING NORTHWARD THROUGH THE GULF OF MEXICO AND A COLD FRONT
APPROACHING FROM THE NORTHWEST WILL KEEP THINGS UNSETTLED DURING
THE EARLY TO MIDDLE PART OF NEXT WEEK. HIGH PRESSURE WILL THEN
BUILD BACK INTO THE REGION BY THURSDAY AND REMAIN THE DOMINANT
WEATHER FEATURE THROUGH THE FIRST PART OF THE UPCOMING WEEKEND.
NEAR TERM /UNTIL 6 AM THIS MORNING/
SURFACE HIGH PRES EXTENDS E-W OVER OUR FORECAST AREA THIS EVENING.
SKIES ARE CLEAR AND WINDS ARE CALM. CONDITIONS ARE QUITE FAVORABLE
FOR STRONG RADIATIONAL COOLING. PATCHY FROST SEEMS LIKELY OVER
LOCATIONS ADJACENT TO THE CSRA AND SE MIDLANDS REGIONS. THE
GREATEST FROST POTENTIAL WILL OCCUR ROUGHLY N OF A PERKINS-
HILLTONIA-CROCKETVILLE-SMOAKS LINE. WE BELIEVE THAT FROST SHOULD
BE RELATIVELY PATCHY...ALTHOUGH WE WOULD NOT BE TOO SURPRISED TO
SEE ISOLATED LOCATIONS SUCH AS ALLENDALE BRIEFLY REACH 35-36
DEGREES TOWARD DAWN...SUGGESTING A VERY LOCALIZED POTENTIAL FOR
SLIGHTLY GREAT FROST COVERAGE.
SHORT TERM /6 AM THIS MORNING THROUGH 6 AM MONDAY/
HIGH PRESSURE BOTH AT THE SURFACE AND ALOFT WILL HOLD OVER THE
REGION SUNDAY. TROPICAL CYCLONE IDA OVER THE WESTERN CARIBBEAN IS
FORECAST BY NHC TO MOVE THROUGH THE YUCATAN CHANNEL SUNDAY
AFTERNOON. THE GRADIENT BETWEEN THE HIGH TO THE NORTH AND IDA WILL
BEGIN TO TIGHTEN SUNDAY AFTERNOON BUT WINDS LOOK TO GO NO HIGHER
THAN 10-15 MPH. A WEAK AND DIFFUSE COASTAL TROUGH OFFSHORE WILL
BECOME ABSORBED THE THE SYNOPTIC EASTERLY FLOW DURING THIS TIME
AND WILL HAVE LITTLE IF ANY SIGNIFICANT IMPACT ON ANY SENSIBLE
WEATHER ELEMENTS AS IT DISSIPATES. SLIGHTLY HIGHER DEWPOINTS COULD
SUPPORT A BIT MORE IN THE WAY OF SHALLOW CUMULUS FROM LATE MORNING
THROUGH THE MID AFTERNOON HOURS...BUT STILL EXPECT SUNNY TO MOSTLY
SUNNY SKIES TO PREVAIL WITH A FEW HOURS OF PARTLY CLOUDY CONDITIONS
POSSIBLE ALONG THE I-95 CORRIDOR FROM SAVANNAH SOUTH. HIGHS WILL
REACH IN THE MID-UPPER 70S PER LOW-LEVEL THICKNESS PROGS EXCEPT
AT THE BEACHES WHERE CONSIDERABLY COOLER CONDITIONS WILL BE FOUND.
LONG TERM /MONDAY THROUGH SATURDAY/
MEDIUM RANGE GUIDANCE IS IN DECENT AGREEMENT THROUGHOUT THE EXTENDED
PERIODS THIS AFTERNOON...WITH SOME DIFFERENCES NOTED WITH RESPECT TO
THE EVOLUTION OF TROPICAL CYCLONE IDA OR THE REMNANTS OF THE SYSTEM
DURING THE EARLY TO MID WEEK TIME FRAME.
AN UPPER TROUGH MOVING THROUGH THE SOUTHERN PLAINS INTO THE LOWER
MISSISSIPPI VALLEY IN COMBINATION WITH DEEP LAYER RIDGING OVER THE
WESTERN ATLANTIC...WILL LIFT TROPICAL CYCLONE IDA OR THE REMNANTS OF
THE SYSTEM NORTHWARD THROUGH THE GULF OF MEXICO SUNDAY NIGHT THROUGH
TUESDAY. INITIALLY THE DRY AIRMASS IN PLACE...LACK OF ANY DEEP
MOISTURE AND ANY SIGNIFICANT FORCING FOR ASCENT...SHOULD PRECLUDE
MUCH IN THE WAY OF RAINFALL POTENTIAL. CAN/T RULE OUT A STRAY SHOWER
ROLLING IN OFF THE ATLANTIC MONDAY AFTERNOON...BUT FOR NOW WILL
CONTINUE WITH A RAIN FREE FORECAST SUNDAY NIGHT THROUGH MONDAY. DEEP
TROPICAL MOISTURE WILL STEADILY INCREASE ACROSS THE FORECAST AREA
TUESDAY...AND WITH BOTH ISENTROPIC ASCENT AND DYNAMIC FORCING
SWINGING INTO THE REGION...WILL CARRY LIKELY POPS ALL AREA.
A STRONG UPPER LEVEL TROUGH WILL THEN SHIFT EASTWARD THROUGH THE
EASTERN GREAT LAKES AND NEW ENGLAND STATES TUESDAY NIGHT...ALLOWING
A SURFACE COLD FRONT TO PUSH SOUTHEASTWARD THROUGH THE FORECAST
AREA. STRONG HIGH PRESSURE WILL BUILD NORTH OF THE REGION WEDNESDAY
THROUGH THURSDAY...BEFORE SHIFTING INTO THE WESTERN ATLANTIC FOR THE
TAIL END OF THE WORK WEEK AND INTO THE FIRST PART OF THE UPCOMING
WEEKEND. WILL CARRY LIKELY POPS TUESDAY NIGHT AS DEEP MOISTURE AND
FORCING WILL REMAIN IN PLACE ACROSS THE FORECAST AREA AS THE COLD
FRONT PUSHES SOUTHWARD THROUGH THE AREA. STILL SOME TIMING
DISCONTINUITIES IN THE MODELS WITH RESPECT TO HOW QUICKLY THE COLD
FRONT PUSHES THROUGH THE AREA...SO WILL KEEP CHANCE POPS GOING
THROUGH THE DAY WEDNESDAY. HIGH PRESSURE WILL BECOME MORE DOMINANT
WEDNESDAY NIGHT THROUGH SATURDAY...SO WILL MAINTAIN THE RAIN FREE
FORECAST. DEPENDING ON HOW THE POSITIONING OF THE RIDGE AXIS NORTH
OF THE REGION THURSDAY THROUGH SATURDAY...THERE IS A POTENTIAL FOR
SOME SHOWERS TO PUSH ONSHORE OFF THE ATLANTIC...BUT PROBABILITIES
APPEAR TOO LOW TO MENTION IN THE FORECAST AT THIS TIME.
AVIATION /06Z SUNDAY THROUGH THURSDAY/
VFR CONDITIONS WILL PREVAIL AT KCHS AND KSAV THROUGH 06Z MONDAY.
CLEAR SKIES AND CALM WINDS WILL PERSIST INTO MID-MORNING...
WITH AN EASTERLY FLOW DEVELOPING LATE THIS MORNING AND THIS
AFTERNOON WITH SPEEDS LESS THAN 10 KT. THE ONSHORE FLOW COULD
RESULT IN A FEW STRATOCUMULUS DEVELOPING DURING THE AFTERNOON NEAR
KSAV...OTHERWISE SOME INCREASING HIGH CLOUDINESS IS EXPECTED FROM
THE SOUTH TODAY INTO TONIGHT.
EXTENDED AVIATION OUTLOOK....VFR CONDITIONS WILL PREVAIL THROUGH
MON. POTENTIAL FOR MVFR OR IFR CONDITIONS MON NIGHT THROUGH WED.
LLWS ALSO POSSIBLE WED MORNING. VFR CONDITIONS EXPECTED WED NIGHT
INTO THU.
MARINE
NORTHEAST WINDS WILL INCREASE TO 10-15 TONIGHT ACROSS MUCH OF OUR
MARINE AREA AS THE GRADIENT TIGHTENS BETWEEN HIGH PRES INLAND AND
A WEAK COASTAL TROUGH DEVELOPING OFFSHORE. SEAS 2 TO 3 FT NEAR
SHORE...BUILDING TO 3-4 FT OFFSHORE.
NORTHEAST WINDS WILL CONTINUE INTO SUNDAY BUT COULD LOCALLY VEER
EASTERLY NEAR THE COAST AS A RESULTANT SEA BREEZE CIRCULATION
DEVELOPS. SPEEDS OF 10-15 KT WILL PERSIST WITH SEAS WILL BUILD TO
2-4 FT NEARSHORE WATERS AND 4-5 FT OFFSHORE WATERS.
SUNDAY NIGHT THROUGH THURSDAY...HIGH PRESSURE OVER THE WESTERN
ATLANTIC IN COMBINATION WITH TROPICAL CYCLONE IDA OR THE REMNANTS
OF THE SYSTEM TRACKING NORTHWARD THROUGH THE GULF OF MEXICO...WILL
RESULT IN AN INCREASING GRADIENT ACROSS THE COASTAL WATERS SUNDAY
NIGHT THROUGH TUESDAY. A STRONG COLD FRONT WILL MOVE THROUGH THE
REGION TUESDAY NIGHT...WITH A POTENTIALLY SIGNIFICANT SURGE IN THE
WINDS BEHIND THE SYSTEM THROUGH THURSDAY AS A STRONG RIDGE OF HIGH
PRESSURE BUILDS NORTH OF THE REGION. SMALL CRAFT CONDITIONS FOR
WINDS/SEAS OR A COMBINATION OF THE TWO MAY DEVELOP AS EARLY AS
SUNDAY NIGHT ACROSS THE OUTER GEORGIA WATERS...WITH SMALL CRAFT
CONDITIONS EXPECTED TO MOVE INTO THE NEARSHORE WATERS MONDAY OR
MONDAY NIGHT. SMALL CRAFT CONDITIONS ARE THEN EXPECTED TO CONTINUE
FOR ALL WATERS WITH THE EXCEPTION OF CHARLESTON HARBOR THROUGH
THURSDAY. HEADLINE THRESHOLDS MAY NOT BE REACHED IN CHARLESTON
HARBOR THROUGH TUESDAY...BUT SMALL CRAFT CONDITIONS APPEAR FAIRLY
LIKELY TUESDAY NIGHT THROUGH WEDNESDAY NIGHT AS THE STRONG WIND
SURGE DEVELOPS BEHIND THE COLD FRONTAL PASSAGE. IN FACT DEPENDING
ON THE POSITIONING AND STRENGTH OF HIGH PRESSURE TO THE NORTH AND
THE TROPICAL OR SUBTROPICAL SYSTEM TO THE SOUTH...GALE CONDITIONS
MAY BE REACHED ACROSS PORTIONS OF THE WATERS IN THE TUESDAY NIGHT
THROUGH WEDNESDAY NIGHT TIME FRAME.
CHS WATCHES/WARNINGS/ADVISORIES
GA...NONE.
SC...NONE.
MARINE...NONE.
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