Special Weather Statement, NWS Charleston, SC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
414 PM EDT WED SEP 28 2011

.SYNOPSIS...
A TROUGH OF LOW PRESSURE WILL MOVE OFFSHORE LATE TONIGHT INTO EARLY
SATURDAY...WITH A STRONG COLD FRONT THEN EXPECTED TO MOVE THROUGH
FRIDAY AFTERNOON AND EVENING. HIGH PRESSURE WILL THEN PROVIDE A
COOLER AND DRIER AIR MASS THIS WEEKEND INTO NEXT WEEK.

&&

.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
CONVECTION HAS INITIATED AND MAINLY FAVORS AREAS CLOSER TO THE SC
MIDLANDS AND THE NE CORNER OF THE FORECAST AREA ACROSS EASTERN
CHARLESTON COUNTY. I HAVE ADJUSTED POPS ACCORDINGLY AND HAVE THE
HIGHEST POPS FURTHER INLAND ACROSS THE SC ZONES CLOSEST TO THE
ONGOING STORM ACTIVITY. THE BOUNDARY THAT HAS REMAINED DRAPED
ACROSS THE DEEP SOUTH...WESTERN CAROLINAS...AND NE INTO THE
CENTRAL PA HAS FINALLY STARTED TO PUSH EASTWARD THIS AFTERNOON.
DEWPOINTS ARE NOW IN THE 50S ACROSS N GA AND THE UPSTATE AND THIS
DRIER AIR WILL CONTINUE TO WORK ITS WAY INTO THE REGION THROUGH
THE OVERNIGHT. THE LARGE CLOSED UPPER LOW POSITIONED NW OF THE
FORECAST AREA HAS SHOWN SOME EASTWARD DRIFT THE LAST FEW HOURS AND
WILL CONTINUE TO MOVE EASTWARD THROUGH THURSDAY MORNING AS A SHARP
H5 TROF DIVES ACROSS THE N PLAINS AND UPPER MIDWEST. THIS WILL
HELP DRIVE THE SURFACE MOISTURE BOUNDARY/WEAK SURFACE TROF
OFFSHORE THROUGH THURSDAY MORNING. I THINK THE MAIN ACTION FROM A
POP STANDPOINT WILL BE THE SHOWERS AND STORMS THAT ARE GOING ON
NOW. AN AREA OF PRECIP AND THUNDERSTORMS CURRENTLY OVER THE GULF
COAST LOOKS LIKE IT WILL REMAIN SOUTH OF THE FORECAST AREA AS IT
MOVES EASTWARD ACROSS N FL THROUGH THURSDAY MORNING. WILL FEATURE
JUST SLIGHT CHANCE TO CHANCE POPS FOR THROUGH THE
EVENING...SHIFTING OFFSHORE THROUGH THURSDAY MORNING. ONE MORE
MILD NIGHT ON TAP WITH UPPER 60S TO NEAR 70 NEAR THE BEACHES...AND
AS LOW AS THE MID 60S FURTHER INLAND.

&&

.SHORT TERM /6 AM THURSDAY MORNING THROUGH SATURDAY/...
THE PERSISTENT UPPER LEVEL LOW OVER THE GREAT LAKES REGION WILL
QUICKLY OPEN UP INTO A TROUGH AND BECOME ABSORBED BY AN EVEN
STRONGER UPPER LEVEL LOW DROPPING SOUTHEAST OUT OF THE UPPER
MISSISSIPPI VALLEY ON THURSDAY. AT THE SURFACE...A WEAK TROUGH/DEW
POINT BOUNDARY WILL CONTINUE TO SHIFT OFF THE COAST IN THE
MORNING...WITH DRIER AIR OVERSPREADING THE AREA IN ITS WAKE. THE
BULK OF THE PRECIPITATION APPEARS TO BE OFF THE COAST THURSDAY
MORNING AND WITH THE DRIER AIR WORKING INTO THE AREA AS THE DAY
PROGRESSES PLAN TO MAINTAIN A DRY FORECAST. A GOOD AMOUNT OF
SUNSHINE DURING THE DAY COMBINED WITH A DOWNSLOPE WIND COMPONENT
ALOFT WILL MAINTAIN ABOVE NORMAL TEMPERATURES...WITH HIGHS FORECAST
TO BE IN THE UPPER 80S ACROSS THE AREA AWAY FROM THE IMMEDIATE
COAST. NEAR NORMAL LOW TEMPERATURES IN THE LOWER TO MID 60S ARE
EXPECTED THURSDAY NIGHT.

SHORT WAVE ENERGY ROTATING AROUND THE BASE OF A CLOSED UPPER LEVEL
LOW WILL PASS NORTH OF THE REGION ON FRIDAY...PUSHING A STRONG COLD
FRONT ACROSS THE AREA FRIDAY AFTERNOON AND OFFSHORE FRIDAY EVENING.
STRONGER FORCING IN ASSOCIATION WITH THE SHORT WAVE TO THE NORTH AND
SLIGHTLY BETTER MOISTURE COULD RESULT IN SOME SPRINKLES OR LIGHT
SHOWERS FRIDAY AFTERNOON ACROSS THE CHARLESTON TRI-COUNTY AREA...BUT
OVERALL THE LACK OF DEEP MOISTURE SHOULD MAKE IT A DRY FRONTAL
PASSAGE. SOME COMPRESSIONAL HEATING AHEAD OF THE FRONT SHOULD KEEP
HIGH TEMPERATURES WELL INTO THE MID AND UPPER 80S ACROSS THE AREA
FOR ONE LAST DAY.

VERY STRONG COLD AIR ADVECTION WILL DEVELOP IN WAKE OF THE COLD
FRONT FRIDAY NIGHT...ALLOWING TEMPERATURES TO FALL INTO THE LOWER
50S IN MOST AREAS AWAY FROM THE COAST WITHIN A COUPLED NORTHWEST
FLOW.

A CLOSED UPPER LEVEL LOW WILL LIFT NORTHEAST ALONG THE MID-ATLANTIC
COAST ON SATURDAY AS CANADIAN HIGH PRESSURE BUILDS INTO THE REGION
FROM THE NORTHWEST. HIGH TEMPERATURES WILL BE WELL BELOW NORMAL ON
SATURDAY GIVEN THE MAGNITUDE OF COLD AIR ADVECTION TAKING PLACE
ALOFT WITH LOW LEVEL THICKNESS VALUES ONLY SUPPORTING HIGHS AROUND
70 OR IN THE LOWER 70S. HOWEVER...GIVING SOME CONSIDERATION TO THE
DOWNSLOPE FLOW ALOFT IN CONJUNCTION WITH SUNNY SKIES...THE FORECAST
WILL INDICATE HIGHS GENERALLY IN THE MID 70S.

LAKE WINDS...A LAKE WIND ADVISORY WILL LIKELY BE NEEDED ON FRIDAY
NIGHT FOLLOWING THE PASSAGE OF A STRONG COLD FRONT. RELATIVELY WARM
LAKE WATER TEMPERATURES AND STRONG COLD AIR ADVECTION ALOFT WILL
RESULT IN VERY FAVORABLE MIXING PROFILES OVER THE LAKE...WHICH
SHOULD HELP MIX MUCH OF THE 25-30 KT LOW LEVEL WINDS DOWN TO THE
LAKE SURFACE.

&&

.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
ANOTHER STRONG SHORTWAVE TROUGH IS PROGGED TO DIG THROUGH THE BASE
OF THE LONGWAVE TROUGH SUNDAY. THIS SHORTWAVE COULD PRODUCE SOME
CLOUDS BUT THE AIRMASS SHOULD REMAIN TOO DRY TO SUPPORT MEASURABLE
PRECIPITATION.

OTHERWISE...HIGH PRESSURE WILL REMAIN ANCHORED OVER THE REGION WITH
A COOL DRY AIRMASS AT LEAST THROUGH EARLY NEXT WEEK. LATE IN THE
FORECAST PERIOD...AS THE HIGH SHIFTS EAST THE FLOW COULD TURN
ONSHORE...MODIFYING THE AIRMASS AND PROMOTING A SLIGHTLY GREATER
CHANCE FOR A FEW SHOWERS TO PUSH ONSHORE. HOWEVER...THROUGH
WEDNESDAY POPS REMAIN BELOW 15 PERCENT WITH NO EXPLICIT MENTION OF
PRECIPITATION THROUGH MIDWEEK.

&&

.AVIATION /20Z WEDNESDAY THROUGH MONDAY/...
THE FIRST 6-12 HOURS OF THE AVIATION FORECASTS DEPENDS HEAVILY ON
THUNDERSTORM DEVELOP ACROSS THE AREA. IT APPEARS STORMS WILL
REMAIN AWAY FROM KSAV AND ONE SHOWER HAS ALREADY QUICKLY PASSED
OVER KCHS. WILL CONTINUE JUST A CB MENTION AT BOTH SITES INTO THE
EVENING HOURS. OVERNIGHT...EXPECT ANY LINGERING SHOWERS AND
STORMS TO DISSIPATE THROUGH THE EARLY MORNING HOURS. MODEL AND
STATISTICAL GUIDANCE GIVES SOME DEGREE OF CIG AND VSBY
RESTRICTIONS THURSDAY MORNING...MAINLY AT KSAV. I HAVE OPTED TO
LEAVE OUT FOR NOW AS VSBYS COULD BE DEPENDENT ON AFTERNOON
THUNDERSTORM ACTIVITY AND RESULTING RAINFALL. ON THURSDAY...DRIER
AIR WILL BEGIN TO FILTER INTO THE REGION.

EXTENDED AVIATION OUTLOOK...VFR CONDITIONS WILL PREVAIL.

&&

.MARINE...
TONIGHT...THE WEAK SURFACE TROF THAT HAS BEEN NEARLY STATIONARY
JUST INLAND FOR THE PAST FEW DAYS WILL MOVE OFFSHORE AND OVER THE
LOCAL WATERS. THE PRESSURE GRADIENT DOES STRENGTHEN A BIT AND
WINDS WILL BE S TO SW AROUND 10 KTS WITHIN 20 NM...AND 10 TO 15
KTS IN THE OUTER WATERS. SEAS ARE CURRENTLY 2 TO 3 FEET IN THE
FORM OF A 9 TO 10 SECOND SWELL. THIS WILL CONTINUE...IF NOT
DECREASE SLIGHTLY...THROUGH THURSDAY MORNING. OVERALL CONDITIONS
WILL REMAIN BELOW SCA CRITERIA.

FRIDAY THROUGH MONDAY...A SOUTH/SOUTHWEST FLOW WILL PREVAIL FRIDAY
WITH SPEEDS GENERALLY 15 KT OR LESS AND SEAS OF 2-3 FT. A STRONG
COLD FRONT WILL PUSH OFFSHORE FRIDAY EVENING...SHIFTING WINDS
NORTHWEST AND EVENTUALLY NORTH. STRONG COLD AIR ADVECTION IN WAKE
OF THE FRONT WILL LIKELY SUPPORT SMALL CRAFT ADVISORY WINDS AND
POSSIBLY SEAS OVER MOST OF THE COASTAL WATERS AT TIMES THROUGH THE
WEEKEND. ALTHOUGH WINDS COULD DIMINISH A BIT EARLY NEXT WEEK...A
FAVORABLE FETCH WITHIN A NORTHEAST FLOW COULD KEEP SEAS ELEVATED.

RIP CURRENTS...A MODERATE RISK FOR RIP CURRENTS WILL BE MAINTAINED
FOR ALL BEACHES FOR THE REMAINDER OF TODAY DUE TO ONGOING TIDAL AND
LUNAR INFLUENCES...COMBINED WITH A PERSISTENT 3 FT SWELL AROUND 9
SECONDS.

&&

.TIDES/COASTAL FLOODING...
ASTRONOMICAL HIGH TIDES WILL CONTINUE THROUGHOUT THE WEEK...AND
AIDED BY OCCASIONAL INCREASES IN ONSHORE WINDS AND A LITTLE HIGHER
THAN NORMAL SURF...SHALLOW COASTAL FLOODING IS POSSIBLE...ESPECIALLY
ALONG THE SOUTH CAROLINA COAST.

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...NONE.
SC...NONE.
MARINE...NONE.

&&

BSH/JAQ

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SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE CHARLESTON SC
327 PM EDT WED SEP 28 2011

SCZ045-050-282015-
CHARLESTON-INLAND BERKELEY-
327 PM EDT WED SEP 28 2011

...STRONG THUNDERSTORMS WILL IMPACT PORTIONS OF CHARLESTON AND
BERKELEY COUNTIES THROUGH 415 PM EDT...

AT 323 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
STRONG THUNDERSTORM...NEAR DUNES WEST...MOVING EAST AT 20 MPH.

SOME LOCATIONS THAT WILL BE AFFECTED INCLUDE...
AWENDAW...BULL ISLAND...CAPE ISLAND...CAPE ROMAIN...CAPERS INLET...
GARRIS LANDING...HAMPTON PLANTATION STATE PARK...LIGHTHOUSE ISLAND...
MCCLELLANVILLE...MOUNT PLEASANT REGIONAL AIRPORT...PRICE INLET AND
SANTEE COASTAL RESERVE...

PREPARE NOW FOR THE FOLLOWING HAZARDS...
GUSTY WINDS OF 40 TO 50 MPH...
DIME SIZE HAIL...

PRECAUTIONARY/PREPAREDNESS ACTIONS...

BE ALERT FOR RAPIDLY CHANGING WEATHER CONDITIONS AS STORMS APPROACH.
BE READY TO TAKE IMMEDIATE ACTION IN CASE A SEVERE THUNDERSTORM
WARNING IS ISSUED FOR YOUR LOCATION.

&&

LAT...LON 3314 7926 3308 7933 3300 7936 3299 7950
      3303 7952 3301 7955 3299 7954 3301 7955
      3301 7957 3294 7961 3294 7957 3297 7955
      3290 7957 3281 7977 3297 7985 3306 7985
      3325 7948 3316 7935
TIME...MOT...LOC 1928Z 262DEG 17KT 3297 7975

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE CHARLESTON SC
402 PM EDT WED SEP 28 2011

GAZ088-SCZ040-282030-
ALLENDALE-SCREVEN-
402 PM EDT WED SEP 28 2011

...GUSTY WINDS WITH SHOWERS AND THUNDERSTORMS WILL IMPACT PORTIONS
OF SCREVEN AND ALLENDALE COUNTIES THROUGH 430 PM EDT...

AT 359 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED
SHOWERS AND THUNDERSTORMS...ALONG A LINE EXTENDING FROM 6 MILES
NORTH OF MILLETT TO MILLETT...MOVING EAST AT 25 MPH.

SOME LOCATIONS THAT WILL BE AFFECTED INCLUDE...
ALLENDALE...APPLETON...MARTIN...MILLETT AND SEIGLING...

PREPARE NOW FOR THE FOLLOWING HAZARDS...
GUSTY WINDS OF 40 TO 50 MPH...

PRECAUTIONARY/PREPAREDNESS ACTIONS...

ALTHOUGH LITTLE OR NO LIGHTNING IS OCCURRING...THIS STORM IS CAPABLE
OF PRODUCING GUSTY WINDS WHICH MAY BLOW OVER TENTS...OUTDOOR
FURNITURE...AND HANGING OBJECTS. IF TIME PERMITS SECURE VULNERABLE
OBJECTS AND GO INSIDE A STURDY SHELTER.

BE ALERT FOR RAPIDLY CHANGING WEATHER CONDITIONS AS STORMS APPROACH.
BE READY TO TAKE IMMEDIATE ACTION IN CASE A SEVERE THUNDERSTORM
WARNING IS ISSUED FOR YOUR LOCATION.

&&

LAT...LON 3302 8159 3304 8157 3305 8157 3308 8162
      3310 8162 3316 8154 3311 8136 3312 8123
      3287 8133 3299 8163
TIME...MOT...LOC 2002Z 277DEG 20KT 3316 8150 3304 8158

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE CHARLESTON SC
412 PM EDT WED SEP 28 2011

SCZ045-050-282100-
CHARLESTON-INLAND BERKELEY-
412 PM EDT WED SEP 28 2011

...STRONG THUNDERSTORMS WILL IMPACT PORTIONS OF CHARLESTON AND
BERKELEY COUNTIES THROUGH 500 PM EDT...

AT 408 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED
STRONG THUNDERSTORMS...ALONG A LINE EXTENDING FROM TIBWIN TO GARRIS
LANDING...MOVING NORTHEAST AT 10 MPH.

SOME LOCATIONS THAT WILL BE AFFECTED INCLUDE...
AWENDAW...BULL ISLAND...CAPE ISLAND...CAPE ROMAIN...GARRIS LANDING...
HAMPTON PLANTATION STATE PARK...LIGHTHOUSE ISLAND...MCCLELLANVILLE
AND SANTEE COASTAL RESERVE...

PREPARE NOW FOR THE FOLLOWING HAZARDS...
GUSTY WINDS OF 40 TO 50 MPH...
DIME SIZE HAIL...
FREQUENT CLOUD TO GROUND LIGHTNING...

PRECAUTIONARY/PREPAREDNESS ACTIONS...

FREQUENT CLOUD-TO-GROUND LIGHTNING IS OCCURRING. POSTPONE OUTDOOR
ACTIVITIES PROMPTLY. SEEK SHELTER INSIDE AN ENCLOSED BUILDING.

BE ALERT FOR RAPIDLY CHANGING WEATHER CONDITIONS AS STORMS APPROACH.
BE READY TO TAKE IMMEDIATE ACTION IN CASE A SEVERE THUNDERSTORM
WARNING IS ISSUED FOR YOUR LOCATION.

&&

LAT...LON 3308 7933 3300 7936 3299 7950 3303 7953
      3299 7954 3298 7954 3300 7954 3301 7957
      3294 7961 3294 7957 3297 7955 3290 7957
      3286 7974 3317 7967 3326 7954 3324 7945
      3316 7935 3314 7926
TIME...MOT...LOC 2013Z 243DEG 10KT 3313 7951 3295 7965

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE CHARLESTON SC
414 PM EDT WED SEP 28 2011

SCZ040-282045-
ALLENDALE-
414 PM EDT WED SEP 28 2011

...STRONG THUNDERSTORMS WILL IMPACT PORTIONS OF ALLENDALE COUNTY
THROUGH 445 PM EDT...

AT 412 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
STRONG THUNDERSTORM...NEAR AVERILL...MOVING EAST AT 20 MPH.

SOME LOCATIONS THAT WILL BE AFFECTED INCLUDE...
ALLENDALE...APPLETON...BARTON...FAIRFAX...MARTIN...MILLETT...
SEIGLING...SYCAMORE AND ULMER...

PREPARE NOW FOR THE FOLLOWING HAZARDS...
GUSTY WINDS OF 40 TO 50 MPH...
PENNY SIZE HAIL...

PRECAUTIONARY/PREPAREDNESS ACTIONS...

BE ALERT FOR RAPIDLY CHANGING WEATHER CONDITIONS AS STORMS APPROACH.
BE READY TO TAKE IMMEDIATE ACTION IN CASE A SEVERE THUNDERSTORM
WARNING IS ISSUED FOR YOUR LOCATION.

&&

LAT...LON 3316 8154 3311 8136 3312 8119 3306 8112
      3305 8110 3303 8108 3296 8120 3293 8124
      3291 8133 3298 8150 3301 8149 3306 8158
      3312 8159
TIME...MOT...LOC 2015Z 266DEG 19KT 3311 8147