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000
FXUS62 KCHS 221529
AFDCHS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
1029 AM EST SUN NOV 22 2009
.SYNOPSIS...
AN AREA OF LOW PRES WILL TRACK ALONG THE GULF COAST STATES TODAY
THEN RE-DEVELOP OVER OUR ADJACENT ATLC WATERS TONIGHT. THE LOW
WILL THEN LIFT NE OFF THE CAROLINA COAST MON INTO TUE...AS HIGH
PRES REMAINS ENTRENCHED OVER COASTAL SOUTH CAROLINA AND GEORGIA. A
SERIES OF DRY COLD FRONTS WILL SHIFT THROUGH THE AREA FROM LATE
WEEK INTO THE UPCOMING WEEKEND AS HIGH PRES SLOWLY BUILDS IN FROM
THE W.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
THE UPPER LOW WAS SPINNING ITS WHEELS OVER SOUTHERN ALABAMA THIS
MORNING WHILE THE SURFACE LOW HAD PUSHED INTO THE EASTERN GULF OF
MEXICO. THE VORT MAX ASSOCIATED WITH THE UPPER LOW IS SLOWLY
PUSHING INTO CENTRAL GA TOWARD THE SC MIDLANDS. THE HEAVIEST AND
MOST WIDESPREAD PRECIPITATION HAS BEEN OCCURRING AHEAD OF THIS
FEATURE...MAINLY WEST OF OUR FORECAST AREA. MEANWHILE HIGH
PRESSURE REMAINS ENTRENCHED FROM THE MID-ATLANTIC REGION THROUGH
THE CAROLINAS INTO SOUTHERN GA. DESPITE THE INCREASE IN ISENTROPIC
ASCENT ABOVE THE HIGH PRESSURE WEDGE...A CONSIDERABLE DRY SLOT
OVER THE EASTERN HALF OF THE AREA HAS PREVENTED MUCH IN THE WAY OF
MEASURABLE RAINFALL. LATER THIS AFTERNOON WE SHOULD SEE THE
COASTAL TROUGH OFF THE SC COAST STRENGTHEN WHICH SHOULD IN TURN
IMPROVE RAIN CHANCES ACROSS THE NORTHEASTERN PORTIONS.
HOWEVER...UNTIL THAT OCCURS WE DO NOT EXPECT TO SEE MORE THAN
SCATTERED COVERAGE OF RAIN EAST OF I-95. WE PARED BACK POPS OVER
THE EASTERN HALF OF THE AREA FOR MUCH OF THE DAY ALTHOUGH AT LEAST
LIKELY POPS WILL PREVAIL EVERYWHERE EXCEPT COASTAL CHARLESTON
COUNTY.
THUNDERSTORM POTENTIAL STILL APPEARS VERY LOW BUT AN AREA OF
6-6.5C MID-LEVEL LAPSE RATES MOVING THROUGH THIS AFTERNOON WITH
THE STRONGEST DYNAMICS COULD SUPPORT AN ISOLATED TSTM IN SOUTHERN
AREAS. TEMP FORECAST STILL APPEARS ON TRACK WITH HIGHS REMAINING
IN THE 50S.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH 6 AM MONDAY/...
SURFACE LOW PRES ALONG S ALABAMA AND THE FLORIDA PANHANDLE WILL
WEAKEN BY THIS EVENING...THEN REDEVELOP OFF THE COAST OF THE
GEORGIA/FLORIDA BORDER...THEN TRACK NE ALONG THE W WALL OF THE
GULF STREAM E OF CHARLESTON BY LATE TONIGHT. THIS KEEPS A SOLID
WEDGE PATTERN GOING FOR OUR AREA. TEMPERATURES SHOULD BE COOL AND
FAIRLY STEADY. A PINCHED GRADIENT SUPPORTING BREEZY CONDITIONS
ALONG THE SOUTH CAROLINA COAST SHOULD RELAX LATE TONIGHT AS THE
EJECTING LOW BUCKLES THE WEDGE NW OVER EASTERN SOUTH CAROLINA.
LOCATIONS SUCH AS CHARLESTON...ST. GEORGE AND MONCKS CORNER MAY
SEE THEIR MOST SIGNIFICANT RAINS BETWEEN DUSK AND MIDNIGHT AS THE
DYNAMICS TRAVERSE THE AREA. ISOLATED ELEVATED THUNDER POSSIBLE E
OF I-95 IN SOUTH CAROLINA DURING THE EVENING. LATER TONIGHT...MID
LEVEL DRYING STRIPS UPPER MOISTURE AND LEAVES SOUNDING PROFILES
SUPPORTIVE OF LIGHTER RAINS AND DRIZZLE AFTER MIDNIGHT...ESPECIALLY
OVER SE GEORGIA WHERE PRECIP MAY JUST BE DRIZZLE LATE. NEAR COASTAL
BREEZES SHOULD ALSO SUBSIDE LATE AS THE PRES GRADIENT WEAKENS.
&&
.LONG TERM /MONDAY THROUGH SATURDAY/...
GUIDANCE IS IN GOOD AGREEMENT TRACKING SURFACE LOW PRESSURE
NORTHEASTWARD OFF THE CAROLINA COAST MONDAY THROUGH TUESDAY...WITH
NORTHERLY FLOW STRENGTHENING THE HIGH PRESSURE WEDGE ACROSS THE
FORECAST AREA. DEEP MOISTURE WILL HAVE SHIFTED OUT OF THE REGION BY
DAYBREAK MONDAY...BUT MODEL RELATIVE HUMIDITY TIME/HEIGHT CROSS
SECTIONS CONTINUE TO INDICATE A NEARLY SATURATED BOUNDARY LAYER
ACROSS THE ENTIRE FORECAST AREA THROUGH TUESDAY. GIVEN THE VERY
LIGHT WIND FIELDS OUT OF A NORTH-NORTHEAST THROUGH NORTH-NORTHWEST
DIRECTION AND THE LOW SUN ANGLE...EXPECT THE LOW LEVEL INVERSION TO
HOLD STRONG ACROSS THE AREA...RESULTING IN CLOUDY/MOSTLY CLOUDY
CONDITIONS ALONG WITH SOME LIGHT RAIN AND/OR AREAS OF DRIZZLE
IMPACTING THE REGION THROUGH TUESDAY.
MODEL SOLUTIONS ARE FOR THE MOST PART IN AGREEMENT FOR THE MID-LATE
WEEK TIME FRAME. THE EXCEPTION TO THIS IS THE ECMWF WHICH CONTINUES
TO ADVERTISE DEVELOPMENT OF A WAVE OF LOW PRESSURE TRACKING
NORTHEASTWARD OFF THE GEORGIA AND CAROLINA COAST WEDNESDAY NIGHT AND
THANKSGIVING DAY. GIVEN THE STRONG MODEL CONSENSUS OF THE
GFS/CANADIAN/UKMET SOLUTIONS...AS WELL AS THE ECMWF TRENDING TOWARD
THE SOLUTION OF THE OTHER OPERATIONAL MODELS...WILL KEEP THE
FORECAST RAIN FREE WEDNESDAY THROUGH THANKSGIVING DAY.
HIGH PRESSURE IS THEN EXPECTED TO BUILD BACK INTO THE AREA THURSDAY
NIGHT AND REMAIN THE DOMINANT WEATHER FEATURE THROUGH
SATURDAY...WITH RAIN FREE CONDITIONS ANTICIPATED ACROSS THE REGION.
&&
.AVIATION /15Z SUNDAY THROUGH THURSDAY/...
DETERIORATING CONDITIONS ON TAP TODAY...INITIALLY AT KSAV WHERE IFR
CIGS AND OCNL IFR VSBYS IN MODERATE RAINS ARE EXPECTED BY LATE
MORNING. AT KCHS...A SOMEWHAT DRIER LOW LEVEL AIR MASS MAY TAKE
AT BIT LONGER TO SATURATE THIS AFTERNOON. WE CONTINUED THE
PREVIOUS TREND OF INTRODUCING MVFR CIGS/VSBYS BY EARLY AFTERNOON
THEN IFR CONDITIONS LIKELY BY MID TO LATE AFTERNOON. NE SURFACE
WINDS WILL BE ON THE INCREASE AT BOTH TERMINALS TODAY AS THE PRES
GRADIENT TIGHTENS.
THIS EVENING INTO THE OVERNIGHT...RAINS WILL EVENTUALLY TAPER TO
DRIZZLE WITH POTENTIAL FOR LIFR CONDITIONS AT BOTH AIRPORTS AFTER
06Z/23. AT KSAV...MODELS ARE HITTING LOWER CIGS AND POSSIBLY
VSBYS 1/2 TO 1 MILE IN FOG AND DRIZZLE OVERNIGHT. KCHS SHOULD LOCK
IN WITH CIGS AT OR BELOW 500 FT AFTER MIDNIGHT BUT WITH WINDS
STAYING UP LONGER...VSBYS ARE NOT EXPECTED TO GET AS LOW AS KSAV.
EXTENDED AVIATION OUTLOOK...IFR CONDITIONS ARE LIKELY MON INTO TUE.
VFR CONDITIONS MAY RETURN WED THROUGH THU.
&&
.MARINE...
WINDS AND SEAS CONTINUE TO INCREASE THIS MORNING AS THE SURFACE WEDGE
DIGS IN FROM THE N AND PRES FALLS INCREASE OVER THE NE GULF OF MEXICO
AND N FLORIDA. WE HAVE RAISED SMALL CRAFT ADVISORIES FOR ALL
WATERS INCLUDING THE CHARLESTON HARBOR TODAY. A PINCHED GRADIENT
WILL GRADUALLY TILT NW INTO COASTAL SOUTH CAROLINA LATE TODAY AND
THIS EVENING...WITH NE WINDS BUILDING TO 20 TO 25 KT...LOCALLY
GUSTIER CONDITIONS POSSIBLE. IN SE GEORGIA...WINDS REACHING NEAR
20 KT AT THE SAVANNAH RIVER ENTRANCE AND POSSIBLY A BIT FURTHER S
SUGGEST SEAS AT LEAST 4-6 FT TODAY.
A WAVE OF LOW PRESSURE WILL TRACK NORTHEAST OFF THE CAROLINA
COAST MONDAY THROUGH TUESDAY...AS SURFACE HIGH PRESSURE REMAINS
STATIONARY OVER SOUTH CAROLINA AND GEORGIA AS WELL AS THE
NEARSHORE COASTAL WATERS. A WEAK COLD FRONT WILL THEN SHIFT
THROUGH THE WATERS WEDNESDAY NIGHT...WITH HIGH PRESSURE THEN
BUILDING BACK INTO THE AREA FOR THURSDAY.
COULD SEE SOME LINGERING SMALL CRAFT CONDITIONS THROUGH MONDAY
MORNING DUE TO ELEVATED SEAS OVER THE NORTHERN SOUTH CAROLINA
NEARSHORE WATERS AND THE OFFSHORE GEORGIA WATERS.
THEREFORE...EXTENDED THE SMALL CRAFT ADVISORY FOR THESE MARINE ZONES
THROUGH LATE MONDAY MORNING. ELSEWHERE...WINDS AND SEAS ARE EXPECTED
TO REMAIN BELOW SMALL CRAFT THRESHOLDS THROUGH THURSDAY.
&&
.CHS WATCHES/WARNINGS/ADVISORIES...
GA...NONE.
SC...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL MIDNIGHT EST TONIGHT FOR AMZ330-352-
354.
SMALL CRAFT ADVISORY UNTIL 11 AM EST MONDAY FOR AMZ350-374.
&&
$$
JRL
