Special Weather Statement, NWS Charleston, SC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
332 PM EDT SAT AUG 11 2012

.SYNOPSIS...
A WEAK COLD FRONT WILL MOVE OFF THE COAST SUNDAY...THEN STALL
OFFSHORE SUNDAY NIGHT INTO MONDAY BEFORE DISSIPATING. ANOTHER
WEAK FRONT WILL MOVE IN DURING THE MIDDLE OF THE WEEK WITH A
MUCH STRONGER COLD FRONT IMPACTING THE AREA NEXT WEEKEND.

&&

.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
NUMEROUS TO WIDESPREAD SHOWERS/TSTMS CONTINUE TO MARCH EAST ACROSS
SOUTHEAST SOUTH CAROLINA AND SOUTHEAST GEORGIA THIS AFTERNOON. THE
RISK FOR SEVERE WEATHER IS GENERALLY DIMINISHING NOW THAT THE
ATMOSPHERE HAS GENERALLY BEEN OVERTURNED. THE ONLY EXCEPTION IS
IN A NARROW CORRIDOR ALONG THE COAST FROM TYBEE ISLAND UP THROUGH
THE CHARLESTON METRO AREA WHERE INSTABILITY PERSISTS AHEAD OF THE
INITIAL LINE OF TSTMS. SHORT TERM MODELS ARE PRETTY CONSISTENT IN
SHOWING A DRAMATIC DECREASE IN THE COVERAGE OF SHOWERS/TSTMS BY
LATE AFTERNOON AS INSTABILITY WANES IN THE WAKE OF WIDESPREAD
CONVECTION. THE LATE AFTERNOON PACKAGE WILL FOLLOW SUITE WITH
CATEGORICAL POPS DROPPING TO CHANCE POPS PRIOR TO SUNRISE WITH
SLIGHT CHANCE POPS PREVAILING BY MID-LATE EVENING. EXPECT DRY
AND CLEARING CONDITIONS TO DOMINATE FROM MIDNIGHT THROUGH SUNRISE
SUNDAY. LOWS WILL RANGE FROM THE LOWER 70S INLAND TO THE UPPER 70S
AT THE BEACHES AND IN DOWNTOWN CHARLESTON.

&&

.SHORT TERM /6 AM SUNDAY MORNING THROUGH TUESDAY/...
AN UPPER TROUGH ALONG THE EAST COAST SUNDAY MORNING WILL QUICKLY
LIFT OUT TO THE NORTHEAST AND WILL BE REPLACED BY ANOTHER EAST COAST
UPPER TROUGH BY LATE TUESDAY. THE CHANGES IN THE UPPER LEVEL PATTERN
ARE HANDLED SIMILARLY BY THE MODELS WITH THE ONLY OUTLIER BEING THE
00Z ECMWF WHICH HAS A FLATTER UPPER TROUGH BY TUESDAY COMPARED TO
THE 12Z GFS AND 12Z NAM.

DEEP TROPICAL MOISTURE WITH PRECIPITABLE WATER VALUES FROM 1.5 TO 2
INCHES WILL BE IN PLACE ACROSS THE AREA 12Z SUNDAY MORNING AS A WEAK
COLD FRONT MOVES OFF THE COAST. BEST RAIN CHANCES EXPECTED DURING
THE MORNING HOURS ALONG THE COAST...WITH THE RAIN THREAT SHIFTING
OFF THE COAST BY NOON. MAINTAINED SLIGHT CHANCE FOR SHOWERS AND
THUNDERSTORMS SUNDAY MORNING ALONG THE COAST. BEHIND THE
FRONT...EXPECT CLOUDS TO LINGER...BUT DO EXPECT A DECENT AMOUNT OF
SUNSHINE ESPECIALLY DURING THE AFTERNOON HOURS. DUE TO THE
EXPECTATION THAT THE CLOUD COVER WILL LINGER A LITTLE LONGER THAN
PREVIOUSLY THOUGHT...LOWERED HIGH TEMPERATURES SUNDAY A DEGREE OR
TWO IN MOST AREAS AND THIS IS MORE IN LINE WITH THE GFS GUIDANCE.
THE NAM IS MORE AGGRESSIVE WITH REGARDS TO MAINTAINING SIGNIFICANT
CLOUD COVER AND KEEPS HIGHS MAINLY IN THE UPPER 80S. FOR NOW...AM
FORECASTING HIGHS FAIRLY CLOSE TO 90 IN MOST AREAS AWAY FROM THE
BEACHES. MAINTAINED A SLIGHT CHANCE FOR SHOWERS AND THUNDERSTORMS
MAINLY IN SOUTHEAST GEORGIA FOR A FEW HOURS IN THE AFTERNOON...BUT
CONFIDENCE IN THIS OCCURRING IS NOT THAT GREAT AND WILL BE HIGHLY
DEPENDENT ON GETTING A DECENT AMOUNT OF SUNSHINE.

ANY LEFTOVER PRECIPITATION WILL DIMINISH QUICKLY SUNDAY
EVENING...FOLLOWED BY MAINLY CLEAR SKIES. WITH A LITTLE DRIER AIR
BEING ADVECTED IN OVERNIGHT...EXPECT A RELATIVELY COOL NIGHT
COMPARED TO MUCH OF THE SUMMER WITH LOWS MAINLY IN THE UPPER 60S TO
LOWERS 70S...WITH MID 70S NEAR THE COAST.

DOWNSLOPE WINDS MONDAY MORNING BEHIND THE WEAK COLD FRONT WILL
ALLOW TEMPERATURES TO WARM QUICKLY AND WITH GOOD MIXING AND
PRECIPITABLE WATER VALUES DOWN TO JUST OVER ONE INCH...EXPECT
DEWPOINTS TO MIX OUT SOME DURING THE DAY. LOWERED DEWPOINTS MONDAY
SOME...BUT DID NOT GO QUITE AS LOW AS WAS DEPICTED BY THE GFS
GUIDANCE WHICH SHOWS LOWER TO MID 60S IN MOST INLAND LOCATIONS
DURING THE AFTERNOON. MODELS SHOW A STABLE AIRMASS ACROSS THE AREA
EVEN DURING PEAK HEATING TIME SO MAINTAINED A RAIN FREE FORECAST.
EXPECT HIGHS ON MONDAY MAINLY TO BE IN THE LOWER TO PERHAPS MID 90S
AWAY FROM THE COAST WITH UPPER 80S TO NEAR 90 AT THE BEACHES.

TUESDAY THE FORECAST BECOMES A BIT MORE UNCERTAIN GIVEN THE
DIFFERENCES BETWEEN THE GFS AND ECMWF. THE 12Z GFS BRINGS DEEP
MOISTURE WITH PRECIPITABLE WATER VALUES OVER 2 INCHES BACK INTO THE
AREA AND SOME UPPER LEVEL SUPPORT FOR LIFT WHICH WOULD LEAD TO LOWER
HIGH TEMPERATURES AND COMBINED WITH AN INLAND SURFACE TROUGH WOULD
LEAD TO A CHANCE FOR SHOWERS AND THUNDERSTORMS. THE 00Z ECMWF HAS
MUCH LESS MOISTURE ACROSS THE AREA AND NO LEE SIDE SURFACE TROUGH.
THE MOST LIKELY SCENARIO IS THAT WE WILL SEE SOME CONVECTION
INITIATE MAINLY IN THE AFTERNOON WITH PERHAPS SOME UPSTREAM STORMS
MIGRATING TOWARD THE COAST LATE AFTERNOON INTO THE EVENING....WITH
THE BEST THREAT FOR RAIN ACROSS SOUTHEAST GEORGIA AWAY FROM THE
COAST. IN THIS AREA HAVE UPPED POPS JUST SLIGHTLY INTO THE CHANCE
CATEGORY. ELSEWHERE...WILL CONTINUE WITH A SLIGHT CHANCE FOR SHOWERS
AND THUNDERSTORMS.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
THE EXTENDED PERIOD IS QUITE UNCERTAIN GIVEN LARGE DIFFERENCES
BETWEEN THE SYNOPTIC SCALE MODELS. RELATIVELY QUIET CONDITIONS
EXPECTED WEDNESDAY AND THURSDAY UNDER SHORTWAVE RIDGING. HOWEVER
LATE WEEK INTO THE WEEKEND A HIGHLY AMPLIFIED UPPER TROUGH WILL
SHIFT TOWARD THE EASTERN UNITED STATES AND POTENTIALLY BRING A COLD
FRONT TO THE AREA WITH AN INCREASE IN RAIN CHANCES. TEMPS LOOK TO
CONTINUE NEAR OR SLIGHTLY ABOVE NORMAL FOR MID-AUGUST.

&&

.AVIATION /20Z SATURDAY THROUGH THURSDAY/...
SHOWERS/TSTMS ARE STEADILY EXPANDING WEST OF KSAV/KCHS EARLY THIS
AFTERNOON. THIS ACTIVITY WILL MOVE EAST AND LIKELY IMPACT BOTH
TERMINALS BY MID-LATE AFTERNOON. THE WINDOW FOR GREATEST IMPACTS
WILL BE FROM 19-21Z FOR KSAV AND 20-23Z FOR KCHS. WILL SHOW A
TEMPO GROUP OF HIGH-END IFR/LOW-END MVFR TO COVER FOR THESE TIME
FRAMES. ACTIVITY COULD LINGER AROUND KCHS A BIT LONGER SO MAY NEED
TO CONSIDERING LENGTHENING A MENTION OF TSRA. AMENDMENTS WILL
LIKELY BE NEEDED THROUGHOUT THE AFTERNOON AS TRENDS/IMPACTS BECOME
MORE APPARENT. VFR EXPECTED TO DOMINATE DURING THE OVERNIGHT
HOURS WITH A LOW RISK FOR SHALLOW GROUND FOG DEVELOPING AT EITHER
TERMINAL PRIOR TO SUNRISE IF CLOUDS THIN ENOUGH.

EXTENDED AVIATION OUTLOOK...ISOLATED CONVECTION POSSIBLE TUESDAY
AND WEDNESDAY.

&&

.MARINE...
THERE WILL BE A RISK FOR STRONG TSTMS TO IMPACT THE WATERS LATE
THIS AFTERNOON AS TSTMS MOVE OFF THE COAST. SPECIAL MARINE
WARNINGS MAY BE NEEDED FOR SOME MARINE ZONES. OTHERWISE...THERE
ARE NO MAJOR CONCERNS WITH WINDS GENERALLY 15 KT OR LESS OUTSIDE
OF TSTM AND SEAS 4 FT OR LESS.

WINDS WILL REMAIN GENERALLY SOUTHWESTERLY SUNDAY THROUGH THURSDAY
WITH SEAS AT OR BELOW 4 FT. THE STRONGEST OFFSHORE WINDS WILL OCCUR
AT NIGHT DURING NOCTURNAL SURGES WHILE THE AFTERNOON SEABREEZE
ENHANCES THE WIND SPEED ALONG THE COAST.

&&

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

&&

SYNOPSIS...
NEAR TERM...
SHORT TERM...
LONG TERM...
AVIATION...
MARINE...

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE CHARLESTON SC
1029 AM EDT SAT AUG 11 2012

AMZ330-350-352-354-374-GAZ087-088-099>101-114>119-137>141-SCZ040-
042>045-047>052-120200-
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-INLAND BERKELEY-
INLAND JASPER-BEAUFORT-COASTAL COLLETON-CHARLESTON-COASTAL JASPER-
TIDAL BERKELEY-
1029 AM EDT SAT AUG 11 2012

...ISOLATED SEVERE THUNDERSTORMS POSSIBLE THIS AFTERNOON AND
EVENING...

THIS HAZARDOUS WEATHER OUTLOOK IS FOR ATLANTIC COASTAL
WATERS...SOUTHEAST GEORGIA AND SOUTHEAST SOUTH CAROLINA.

.DAY ONE...TODAY AND TONIGHT.
SEVERE THUNDERSTORMS...NUMEROUS SHOWERS AND THUNDERSTORMS ARE
EXPECTED TO DEVELOP ACROSS SOUTHEAST SOUTH CAROLINA AND SOUTHEAST
GEORGIA THIS AFTERNOON AS A COLD FRONT APPROACHES FROM THE
NORTHWEST. A FEW OF THESE THUNDERSTORMS COULD BECOME SEVERE WITH
DAMAGING WINDS IN EXCESS OF 60 MPH. IN ADDITION...ANY
THUNDERSTORMS THAT DEVELOP TODAY WILL BE CAPABLE OF PRODUCING
FREQUENT CLOUD TO GROUND LIGHTNING AS WELL AS LOCALLY HEAVY
RAINFALL WHICH COULD PRODUCE MINOR FLOODING OF LOW LYING AND POOR
DRAINAGE AREAS. THE RISK FOR ISOLATED SEVERE THUNDERSTORMS WILL
END BY MID EVENING.

PEOPLE ACROSS SOUTHEAST SOUTH CAROLINA AND SOUTHEAST GEORGIA
SHOULD REMAIN ALERT THROUGHOUT THE DAY AND BE PREPARED TO TAKE
ACTION SHOULD THREATENING WEATHER APPROACH OR IF A WARNING IS
ISSUED.

STAY TUNED TO NOAA WEATHER RADIO...TV OR YOUR LOCAL NEWS OUTLET
FOR LATEST HAZARDOUS WEATHER INFORMATION FROM THE NATIONAL WEATHER
SERVICE.

.DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY.

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION IS NOT EXPECTED AT THIS TIME.

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE CHARLESTON SC
354 PM EDT SAT AUG 11 2012

SCZ043-049-112030-
COASTAL COLLETON-INLAND COLLETON-
354 PM EDT SAT AUG 11 2012

...STRONG THUNDERSTORMS WILL IMPACT PORTIONS OF COLLETON COUNTY
THROUGH 430 PM EDT...

AT 350 PM EDT...NATIONAL WEATHER SERVICE METEOROLOGISTS DETECTED A
STRONG THUNDERSTORM...NEAR GREEN POND...MOVING EAST AT 20 MPH.

SOME LOCATIONS THAT WILL BE AFFECTED INCLUDE...
ASHEPOO...BENNETTS POINT AND GREEN POND...

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

PRECAUTIONARY/PREPAREDNESS ACTIONS...

FREQUENT LIGHTNING IS OCCURRING WITH THIS THUNDERSTORM. IF
OUTDOORS...STAY AWAY FROM ISOLATED TALL OBJECTS. IF INDOORS...STAY
AWAY FROM WINDOWS AND DOORS. AVOID USING PLUMBING AND ELECTRICAL
APPLIANCES UNLESS IT IS AN EMERGENCY.

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 3246 8040 3249 8043 3248 8046 3249 8049
      3259 8058 3259 8064 3266 8068 3267 8067
      3267 8072 3280 8061 3272 8042 3267 8042
      3265 8039 3262 8043 3261 8042 3262 8039
      3257 8039 3255 8042 3251 8036
TIME...MOT...LOC 1955Z 253DEG 18KT 3271 8056

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