454
FXUS62 KCHS 202337
AFDCHS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
637 PM EST FRI NOV 20 2009
SYNOPSIS
HIGH PRESSURE WILL BUILD NORTH OF THE REGION THROUGH TONIGHT. A
DEVELOPING GULF LOW PRESSURE SYSTEM WILL MOVE UP THE SOUTHEAST
COAST SATURDAY NIGHT AND SUNDAY. HIGH PRESSURE WILL REBUILD
BEGINNING EARLY NEXT WEEK AND REMAIN THE DOMINANT WEATHER FEATURE
THROUGH MID-WEEK.
NEAR TERM /UNTIL 6 AM SATURDAY MORNING/
HIGH PRESSURE WILL CONTINUE TO RIDGE IN TO THE NORTH TONIGHT...
MAINTAINING A NORTHEAST ONSHORE FLOW OVERNIGHT. THE GRADIENT LOOKS
TO TIGHTEN OVERNIGHT WITH GEOSTROPHIC WINDS INCREASING TO 20-25 KT
BY 12Z SATURDAY. WE SHOULD SEE ANOTHER BATCH OF LOW STRATUS ADVECT
IN FROM THE NORTH OVERNIGHT WHICH WILL PROBABLY AFFECT SIMILAR
PORTIONS OF SOUTHERN SC AS THIS MORNING. FORTUNATELY...FOG DOES
NOT APPEAR TO BE AN ISSUE BECAUSE STRONGER LOW-LEVEL WINDS SHOULD
KEEP THE LOWEST FEW HUNDRED FEET MIXED FAIRLY WELL. LOWS WILL BE
IN THE MIDDLE 40S INLAND WHERE THE WINDS WILL BE LIGHTEST AND SKY
COVER WILL BE MOST LIMITED. ELSEWHERE UPPER 40S TO LOWER 50S
EXPECTED.
SHORT TERM /6 AM SATURDAY MORNING THROUGH 6 PM SATURDAY/
GUIDANCE HAS REALLY BACKED OFF ON BRINGING THE ISENTROPIC
PRECIPITATION INTO THE REGION ON SATURDAY. THE GFS IS NOW THE
OUTLIER SHOWING SOME LIGHT PRECIP BY AFTERNOON AS MOISTURE SPREADS
OUT AHEAD OF THE DEVELOPING GULF LOW. DUE TO THE AMOUNT OF DRY AIR
TO CONTEND WITH...THE CONSENSUS NAM/ECMWF/GEM/HPC SOLUTION OF
MAINLY DRY CONDITIONS THROUGH SATURDAY SEEMS REASONABLE. WE
RESTRICTED THE SLIGHT CHANCE POPS TO SOUTHEAST GA WHERE THE
SLIGHTLY DEEPER MOISTURE WILL EXIST. ALTHOUGH SOME POCKETS OF SUN
ARE LIKELY...IN GENERAL SKIES WILL BE MOSTLY CLOUDY DURING THE
DAY. HIGHS SHOULD REMAIN IN THE UPPER 60S.
LONG TERM /SATURDAY NIGHT THROUGH FRIDAY/
MEDIUM RANGE GUIDANCE IS STILL IN DISAGREEMENT MUCH OF THE PERIOD
LEADING TO LOWER THAN NORMAL CONFIDENCE.
GUIDANCE SOLUTIONS ARE IN GOOD AGREEMENT DEVELOPING AN AREA OF LOW
PRESSURE ALONG THE NORTHERN GULF COAST SATURDAY NIGHT...BUT THEN
DIFFER SOMEWHAT ON THE EVOLUTION/TRACK OF THE SYSTEM. LATEST
THINKING IS THAT THE INITIAL LOW WILL MOVE INLAND ALONG THE GULF
COAST AND DISSIPATE WHILE THEN TRANSFERRING IT/S ENERGY TO THE SE US
COAST SUN NIGHT. DESPITE THE DISAGREEMENT IN TIMING OF THE SYSTEM
THROUGH THE AREA...THE MODELS ARE IN GENERAL AGREEMENT SHOWING AN
INCREASE IN DEEP MOISTURE...PRESENCE OF SOME UPPER LEVEL
FORCING...AND DECENT ISENTROPIC ASCENT OVERSPREADING THE
AREA...MAINLY EARLY SUN THROUGH SUN NIGHT. HAVE LOWERED POPS A BIT
SAT NIGHT BASED ON THE LATEST SREF AND PREFERRED WRF GUIDANCE. STILL
LOOKS LIKE THE BEST CHANCES OF RAIN WILL COME SUN...WITH DECREASING
CHANCES SUN NIGHT. MON LOOKS RATHER DRY EXCEPT FOR FAR NORTHERN
PORTIONS OF THE FORECAST AREA.
MODEL SOLUTIONS CONTINUE TO DIFFER THROUGH MUCH OF THE UPCOMING WORK
WEEK BUT HAVE GENERALLY FOLLOWED THE DRIER GFS WHICH KEEPS A
SOUTHERN STREAM SYSTEM OFF THE SE US COAST LATE IN THE WEEK.
AVIATION /00Z SATURDAY THROUGH WEDNESDAY/
KCHS...THE MAIN CONCERN IS THE POTENTIAL FOR FOG AND/OR STRATUS.
SATELLITE SHOWS A LARGE BATCH OF STRATUS OVER EASTERN NORTH
CAROLINA MOVING SOUTH. MODELS SHOW THE LEADING LEDGE OF THE
STRATUS DECK MOVING INTO THE KCHS TERMINAL AFTER 07Z WITH
PREVAILING MVFR CEILINGS. GUIDANCE STILL SUGGESTS THERE IS A
POTENTIAL FOR OCCASIONAL CEILINGS AS LOW AS 600-800 FT SO HAVE
INCLUDED A TEMPO GROUP FROM 09-12Z FOR IFR CEILINGS. FOG
PARAMETERS ARE NOT AS FAVORABLE AS THIS MORNING...BUT STILL THINK
THERE WILL ENOUGH PATCHY GROUND FOG AROUND TO REDUCE VISIBILITIES
TO 5SM DESPITE THE 15-20 KT 1000MB GEOSTROPHIC FLOW. LOW CLOUDS
WILL GRADUALLY BURN OFF AFTER 15Z SATURDAY WITH VFR CONDITIONS
RETURNING.
KSAV...CURRENT MODEL TRENDS SUGGEST LOW CLOUDS WILL REMAIN NORTH
OF THE KSAV TERMINAL TONIGHT...BUT IT WILL BE CLOSE. WILL KEEP
CEILINGS OUT OF THE TAF...BUT AVIATION INTERESTS SHOULD BE AWARE
THAT THE STRATUS COULD MAKE A RUN FOR THE TERMINAL LATE TONIGHT.
COULD SEE A LITTLE SHALLOW GROUND FOG DEVELOP AFTER 09Z DESPITE
15-20 KT 1000MB GEOSTROPHIC FLOW WITH VISIBILITIES DROPPING TO
HIGH END MVFR THRESHOLDS. VFR CONDITIONS WILL RETURN AFTER 14Z.
EXTENDED AVIATION OUTLOOK...MVFR OR LOWER CEILINGS AND VSBYS
POSSIBLE SAT THROUGH MON. VFR THEREAFTER.
MARINE
HIGH PRESSURE WILL CONTINUE TO STRENGTHEN NORTH OF THE REGION
OVERNIGHT INTO SATURDAY WITH THE PRESSURE GRADIENT TIGHTENING
ACROSS THE COASTAL WATERS. ALTHOUGH NORTHEAST WINDS ARE EXPECTED
TO REMAIN BELOW 20 KNOTS...SEAS SHOULD BUILD TO 4 TO 6 FT OVER THE
OFFSHORE GA WATERS DURING THE DAY SATURDAY. HAVE HOISTED A SMALL
CRAFT ADVISORY BEGINNING AT 6 AM SATURDAY FOR THESE WATERS.
SATURDAY NIGHT THROUGH WEDNESDAY...AN AREA OF LOW PRESSURE ALONG THE
GULF COAST REGION WILL TRANSFER ITS ENERGY TO A DEVELOPING LOW
PRESSURE SYSTEM OFF THE SE US COAST SUN NIGHT/MON. HIGH PRESSURE
WILL THEN BUILD BACK INTO THE AREA FROM THE WEST THROUGH THE MIDDLE
OF NEXT WEEK.
SMALL CRAFT ADVISORY CONDS ARE POSSIBLE ACROSS PORTIONS OF THE
WATERS SATURDAY NIGHT INTO EARLY SUNDAY WITH IMPROVING CONDITIONS
THEN EXPECTED THROUGH WEDNESDAY AS HIGH PRESSURE TAKES CONTROL.
CHS WATCHES/WARNINGS/ADVISORIES
GA...NONE.
SC...NONE.
MARINE...SMALL CRAFT ADVISORY FROM 6 AM SATURDAY TO 10 AM EST SUNDAY
FOR AMZ374.
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page