Damaging Wind in South Carolina, August 12, 2006

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
445 AM EDT SAT AUG 12 2006

.SHORT TERM /TODAY THROUGH MONDAY NIGHT/...OBSERVATIONS SITES AND
MSAS ANALYSIS FIELDS SHOW THE LOCATION OF THE SURFACE FRONT TO BE
APPROXIMATELY ALONG THE SAVANNAH RIVER THIS MORNING. WINDS FROM
TYBEE ISLAND AND NORTH ARE REPORTING NORTHEAST WINDS...WHILE SOUTH
OF THE BOUNDARY WINDS REMAIN WEST TO SOUTHWEST.

NAM INDICATES THE COLD FRONTAL BOUNDARY DROPPING SOUTH THROUGH THE
CWA TODAY AND BELOW THE FORECAST AREA BY THE EVENING HOURS. BEHIND
THE SOUTHWARD DESCENDING FRONT...SEVERAL VORT MAXES MOVE EAST
THROUGH THE SOUTH CAROLINA COUNTIES WHILE ROUNDING THE BASE OF THE
UPPER TROUGH. ABUNDANT LOW LEVEL MOISTURE AND ASSOCIATED FRONTAL
INSTABILITY WILL ALLOW FOR PROMINENT CLOUD COVER THROUGHOUT MOST OF
THE DAY. THIS WILL SUPPRESS DIURNAL HEATING AND INSTABILITY...YET
PROXIMITY OF UPPER TROUGH AND SHORTWAVE ENERGY WILL BE SUFFICIENT TO
KEEP SHOWERS AND THUNDERSTORMS LIKELY. WILL MAINTAIN HIGHEST POPS IN
THE SOUTH CAROLINA ZONES DURING THE DAY...WITH GEORGIA ZONES HAVING
HIGHER POPS DURING THE EVENING AND OVERNIGHT AS THE FRONT AND
ASSOCIATED ENERGY MOVE SOUTH.

QUITE A TEMPERATURE GRADIENT IS POSSIBLE ACROSS THE FORECAST AREA
TODAY. SOUTH CAROLINA ZONES LOCATED NORTH OF THE FRONT WILL ONLY MAX
OUT IN THE MID 80S THIS AFTERNOON...WHILE SOUTHEAST GEORGIA ZONES
COULD STILL RISE TO AROUND 90 DEGREES. LOWS TONIGHT AND INTO SUNDAY
MORNING WILL ALSO BE COOLER...RANGING FROM THE UPPER 60S FAR INLAND
COUNTIES THE MID 70S CLOSER TO THE COAST.

AXIS OF THE UPPER TROUGH MOVES OFFSHORE AND SURFACE HIGH PRESSURE TO
THE NORTHEAST CONTINUES TO RIDGE SOUTHWARD ON SUNDAY. MOST OF THE
ENERGY WILL HAVE DROPPED SOUTH OF THE CWA FOLLOWING THE FRONTAL
BOUNDARY. SHOWER AND THUNDERSTORM CHANCES WILL DECREASE
ACCORDINGLY...AS DRIER AIR ALSO BEGINS TO FILTER DOWN WITHIN A
NORTHEAST FLOW. WITH THE COOLER TEMPERATURES IN PLACE AGAIN ON
SUNDAY...THERE WILL NOT BE THE TYPICAL AFTERNOON SEABREEZE
INSTABILITY TO PROVIDE A FOCUS FOR CONVECTION. GFS MODEL SOUNDING IS
GIVING CAPES BELOW 1000 J/KG...SO CONFIDENCE IS LOW THAT THERE WILL
BE MUCH SHOWER AND THUNDERSTORM ACTIVITY AT ALL. AT THIS POINT WILL
TREND DOWNWARD WITH PROBABILITIES...AND DROP POPS TO SLIGHT CHANCE
ALL ZONES FOR SUNDAY AFTERNOON.

SURFACE PRESSURE DROPS MONDAY AFTERNOON AS THE CENTER OF THE HIGH
MOVES OFFSHORE. LOW LEVEL FLOW WILL VEER FROM NORTHEAST TO SOUTHEAST
DURING THE AFTERNOON...SO EXPECT HIGH TEMPERATURES TO REBOUND INTO
THE UPPER 80S. WITH HIGH PRESSURE ALOFT REBUILDING OVER THE
SOUTHEAST ON MONDAY AND DRY AIR STILL IN PLACE...EXPECT SHOWER AND
THUNDERSTORM DEVELOPMENT TO BE HINDERED ENOUGH TO LEAVE OUT POPS FOR
MONDAY.
&&

.LONG TERM /TUESDAY THROUGH FRIDAY/...NO CHANGES WERE MADE TO THE
EXTENDED FORECAST THIS MORNING.
&&

.MARINE...FRONTAL BOUNDARY IS FOUND ACROSS THE FAR NRN GA WATERS
THIS MORNING...WITH WINDS HAVING RECENTLY SHIFTED TO NE AT TYBEE
ISLAND. FRONT WILL BE SLOW IN PROGRESSING S THRU THE DAY...BUT WITH
DEVELOPING WEDGE AND OVER RUNNING RAINS EXPECTED...WILL SEE THE
FRONT SHIFTING S TODAY...AND CONTINUING S OF THE WATERS TONIGHT.
PINCHED GRADIENT WILL FORM FROM LATE TODAY THRU LATE SUN...AND WITH
FAVORABLE NE FETCH HAVE GONE AHEAD AND ADDED SCA HEADLINES FOR CHS
HARBOR...THE NRN SC WATERS AND THE OUTER GA WATERS.

NE SURGE WILL ALLOW FOR WINDS TO APPROACH 15 OR 20 KT THIS AFTN ON
THE SC WATERS...AND UP TO 15 OR 20 KT LATE TONIGHT OVER THE GA
WATERS. THESE WINDS WILL THEN CONTINUE THRU MUCH OF SUN...BEFORE
DROPPING OFF LATE AND MORE SO SUN NIGHT AND MON AS WEDGE BREAKS
DOWN.

SEAS WILL BUILD WITH THE NE FLOW...CLIMBING UP TO AS HIGH AS 4 TO 6
FT FROM LATE TODAY AND TONIGHT THRU LATE SUN AND SUN NIGHT.

BETTER MARINE CONDITIONS TO SET UP DURING THE EARLY TO MIDDLE PART
OF NEXT WEEK AS ATLC HIGH PRES EXTENDS W ACROSS THE REGION.
&&

.AVIATION...VERY DIFFICULT FCST FOR THE TERMINALS THIS MORNING...AND
CERTAINLY COULD SEE SOME AMENDMENTS THRU THE DAY.

HAVE MAINTAINED MVFR CIGS AT CHS THRU THE FCST PERIOD WITH COOL
ONSHORE FLOW BEHIND THE COOL FRONT...AIDED BY SOME ISENTROPIC
LIFTING AND INVERSION IN THE BOUNDARY LAYER. LOOKS LIKE SEVERAL
HOURS OF RAIN OR SHRA AT CHS...WITH ONLY A SLIGHT RISK OF ELEVATED
CONVECTION THIS AFTN.

AT SAV...HAVE GONE WITH AT LEAST MVFR CONDITIONS THRU 13Z...THEN VFR
CIGS THRU SUNSET. HOWEVER...POTENTIAL EXISTS FOR LOWER CONDITIONS
DURING THIS TIME...WITH ALREADY IFR CIGS SHOWING UP AT TBR AND JYL.
WILL AMEND AS NEEDED.

ALSO LOOKING AT A BETTER CHANCE OF CONVECTION THAN AT CHS DUE TO
CLOSER PROXIMITY TO THE FRONT...AND HAVE INCLUDED VCTS TO ACCOUNT
FOR THIS CHANCE DURING THIS AFTN.
&&

.LAKE WINDS...UNLESS WE ACHIEVE MORE PINCHING OF THE PRES GRADIENT
OR STRONGER CAA THAN IS NOW EXPECTED ACROSS LAKE MOULTRIE...WE ARE
LOOKING AT JUST BELOW LAKE WIND ADVISORY CRITERIA FROM LATE TODAY
THRU LATE SUN. HAVE GONE WITH 15-20 KT DURING THIS TIME AND WILL
CONTINUE TO MONITOR.
&&

.RIP CURRENTS...LOCAL RIP CURRENT WORKSHEET COMES UP WITH A
BORDERLINE LOW TO MODERATE RISK TODAY FOR THE NRN BEACHES. AFTER
COORDINATION WITH ILM WILL KEEP MODERATE RISK GOING FOR CHARLESTON
AND COLLETON BEACHES...BUT LOW RISK ELSEWHERE.
&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...NONE.
SC...NONE.
MARINE...SCA AMZ330 FROM LATE THIS AFTN THRU LATE TONIGHT.
         SCA AMZ350 FROM LATE THIS AFTN THRU LATE SUN AFTN.
         SCA AMZ374 FROM LATE TONIGHT THRU LATE SUN NIGHT.

&&

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HAZARDOUS WEATHER OUTLOOK...UPDATED
NATIONAL WEATHER SERVICE CHARLESTON SC
705 AM EDT SAT AUG 12 2006

AMZ330-350-352-354-374-GAZ087-088-099>101-114>119-137>141-SCZ040-
042>045-047>051-131000-
CHARLESTON HARBOR-
WATERS FROM SOUTH SANTEE RIVER TO EDISTO BEACH SC OUT 20 NM-
WATERS FROM EDISTO BEACH SC TO SAVANNAH GA OUT 20 NM-
WATERS FROM SAVANNAH GA TO ALTAMAHA SOUND GA OUT
20 NM...INCLUDING GRAYS REEF NATIONAL MARINE SANCTUARY-
WATERS FROM SAVANNAH GA TO ALTAMAHA SOUND GA EXTENDING FROM 20 TO
60 NM-JENKINS-SCREVEN-CANDLER-BULLOCH-EFFINGHAM-TATTNALL-EVANS-
INLAND BRYAN-COASTAL BRYAN-INLAND CHATHAM-COASTAL CHATHAM-LONG-
INLAND LIBERTY-COASTAL LIBERTY-INLAND MCINTOSH-COASTAL MCINTOSH-
ALLENDALE-HAMPTON-INLAND COLLETON-DORCHESTER-BERKELEY-
INLAND JASPER-BEAUFORT-COASTAL COLLETON-CHARLESTON-COASTAL
JASPER-
705 AM EDT SAT AUG 12 2006

THIS HAZARDOUS WEATHER OUTLOOK IS FOR SOUTHEAST SOUTH CAROLINA...
SOUTHEAST GEORGIA AND THE ADJACENT COASTAL WATERS FROM THE SOUTH
SANTEE RIVER SOUTH CAROLINA TO ALTAMAHA SOUND GEORGIA.

.DAY ONE...TODAY AND TONIGHT.
.STRONG THUNDERSTORMS...A FEW STRONG THUNDERSTORMS MAY DEVELOP
ACROSS THE AREA TODAY. THESE STORMS ARE MOST LIKELY IN SOUTHEAST
GEORGIA TO THE SOUTH OF I-16. SOME OF THE STORMS COULD PRODUCE
FREQUENT CLOUD TO GROUND LIGHTNING...GUSTY WINDS AND LOCALLY HEAVY
RAINFALL. PLEASE REFER TO THE DAY ONE CONVECTIVE OUTLOOK FOR
ADDITIONAL INFORMATION.

.RIP CURRENTS...A STRONG ONSHORE FLOW...THE RECENT LUNAR PERIGEE AND
THE POSSIBILITY OF SMALL NORTHEAST SWELLS WILL CAUSE A MODERATE RISK
OF RIP CURRENTS ALONG THE CHARLESTON AND COLLETON COUNTY BEACHES
TODAY. PLEASE REFER TO THE SURF ZONE FORECAST FOR ADDITIONAL
INFORMATION.

.DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY.
NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.SPOTTER INFORMATION STATEMENT...
SKYWARN SPOTTER ACTIVATION WILL LIKELY NOT BE NECESSARY.

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