Severe Thunderstorm Warning 145, NWS Charleston, SC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
750 PM EDT FRI JUN 12 2009

.SYNOPSIS...
ON THE PERIPHERY OF AN UPPER RIDGE CENTERED WEST OF THE REGION...
NORTHWEST FLOW ALOFT WILL GUIDE A SERIES OF UPPER LEVEL
DISTURBANCES THROUGH THE AREA INTO NEXT WEEK. MEANWHILE...A COLD
FRONT WILL ADVANCE THROUGH AREA MONDAY OR TUESDAY...AND THIS FRONT
WILL STALL SOUTH OF THE REGION AROUND MIDWEEK. BY LATE
WEEK...THE UPPER RIDGE WILL EXPAND EAST ACROSS THE REGION.

&&

.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
SFC ANALYSIS SHOWS A WEAK LEE SIDE TROUGH OVER THE INLAND
CAROLINAS WHILE ATLC HIGH PRES HOLDS FORT. ALOFT...DEEP RIDGING IN
THE CENTRAL GOMEX WILL CONTINUE TO SLOWLY RETROGRADE TO THE W...
KEEPING A GENERALLY ZONAL FLOW OVER GA AND THE CAROLINAS ALTHOUGH
SEVERAL SHORTWAVE DISTURBANCES ARE RIDING WITHIN THE FLOW. AS THE
RIDGE MOVES AWAY...THE INLAND SFC TROUGH WILL SHIFT TWD THE COAST
THROUGH THIS EVENING. AT THE SAME TIME...ONE PARTICULARLY POTENT
SHORTWAVE TROUGH CROSSING FROM AL INTO GA WILL PUSH TWD THE SC/GA
COAST. THIS SHORTWAVE LOOKS TO BE THE IMPETUS FOR CONVECTION TO
BECOME MORE ORGANIZED FROM NW TO SE OVER THE AREA BY EARLY THIS
EVENING. SOME ISOLD SHWRS/TSTMS HAVE BROKEN OUT OVER THE MIDLANDS
AND NE SC...BUT ACTIVITY HAS HELD OFF FROM STARTING OVER THE CHS
CWFA. THE SEABREEZE BEING PINNED TO THE COAST THUS FAR IS
CONTRIBUTING TO THIS VOID IN THE ACTION...BUT AS THE UPPER
SHORTWAVE APPROACHES AND THE INLAND TROUGH SHIFTS E AND INTERACTS
WITH THE DEEP INSTABILITY...COVERAGE SHOULD INCREASE AND BECOME
MORE ORGANIZED FROM THE NW. IN ADDITION...AS STORMS FORM AND THEN
DISSIPATE...OUTFLOW BOUNDARIES AND INTERACTIONS WITH THE
SEABREEZE SHOULD ALSO HELP SPARK STORMS. CONSIDERING THE CAP HAS
ERODED...CAPE IS NEARLY 4000 J/KG AND LOW LEVEL LAPSE RATES ARE
FAIRLY IMPRESSIVE...ANY STORM THAT FORMS HAS THE POTENTIAL TO
BECOME STRONG TO SEVERE. WILL MAINTAIN MENTION OF THIS POSSIBILITY
IN THE HAZARDOUS WX OUTLOOK.

MIN TEMPS WILL AGAIN REMAIN MILD...RANGING FROM THE UPR 60S/LWR
70S INLAND TO THE MID 70S NEAR THE COASTS.

&&

.SHORT TERM /6 AM SATURDAY MORNING THROUGH SATURDAY NIGHT/...
VERY SIMILAR SYNOPTIC SCENARIO EXPECTED ON SATURDAY WITH ZONAL
WSW-ESE FLOW ALOFT...WEAK LEE SIDE TROFFING INLAND AND HIGH PRES
OVER THE ATLC. WITH DEEP WLY FLOW AGAIN EXPECTED...THE SEABREEZE
SHOULD REMAIN PINNED NEAR THE COAST THROUGH MID-AFTN WHICH WILL
ALLOW FOR GOOD WARMING DURING THE DAY. MAX TEMPS WILL AGAIN REACH
THE LOW-MID 90S. WITH DEWPOINTS AGAIN IN THE LOW-MID 70S...HEAT
INDEX VALUES WILL REACH THE LOW 100S. INSTABILITY WILL AGAIN BE
SUBSTANTIAL...THUS ONCE THE AFTN CAP BREAKS AND CONVECTIVE TEMPS
IN THE UPR 80S ARE REACHED...ISOLD TO SCT CONVECTION CAN BE
EXPECTED. COVERAGE WILL REMAIN IN QUESTION DUE TO THE PINNED
SEABREEZE BUT BEST COVERAGE SHOULD OCCUR DURING THE LATE AFTN
HOURS SO WILL KEEP POPS NO HIGHER THAN 30 ATTM. ISOLD STRONG TO
SEVERE STORMS ARE AGAIN POSSIBLE WITH CAPES OVER 3500 J/KG...
SUFFICIENT LOW LVL LAPSE RATES AND MIDLVL JETTING ARND 30 KT.

NO OVERLY STRONG MIDLVL SHORTWAVE DISTURBANCES ARE EVIDENT ON THE
NAM...GFS OR ECMWF MODELS FOR TMRW SO ANY ONGOING CONVECTION IN
THE EVENING HOURS SHOULD DIMINISH WITH THE LOSS OF DAYTIME
HEATING. WINDS WILL AGAIN SETTLE DOWN AND IT IS POSSIBLE PATCHY
FOG MAY DEVELOP BUT BECAUSE OF LOW CONFIDENCE IN THE COVERAGE...
HAVE HELD OFF FOG MENTION ATTM. MIN TEMPS...JUST LIKE THE PREVIOUS
FEW NIGHTS...WILL AGAIN RUN IN THE UPR 60S/LOW 70S AWAY FROM THE
COAST AND MID 70S NEAR THE SHORES.

&&

.LONG TERM /SUNDAY THROUGH FRIDAY/...
SUNDAY...EXPECT ANOTHER HOT AND HUMID DAY...WITH HIGHS IN THE MID
TO UPPER 90S COMMON AWAY FROM THE COAST. 12Z GUIDANCE SUGGESTS
THAT MID LEVEL CAPPING MAY PREVENT OR GREATLY LIMIT DIURNAL
THUNDERSTORM COVERAGE. FOR THIS FORECAST...SLIGHT CHANCE POPS WILL
SUFFICE DURING THE AFTERNOON.

SUNDAY NIGHT...12Z GUIDANCE SUGGESTS THAT AN MCS MAY PUSH INTO THE
REGION OVERNIGHT. WHILE CONFIDENCE IN THIS SCENARIO REMAINS LOW...
LOW CHANCE POPS ARE JUSTIFIED ESPECIALLY FOR NORTHERN/WESTERN
COUNTIES.

12Z GUIDANCE SUGGESTS THAT A SYNOPTIC COLD FRONT MAY STALL OVER OR
JUST NORTH OF THE FORECAST AREA FOR A TIME MONDAY. THEN...A
SURFACE  WAVE... STRENGTHENING HIGH PRESSURE TO THE NORTH AND
CONTINUED NW FLOW ALOFT SHOULD COMBINE TO PUSH THIS BOUNDARY SOUTH
AS A COLD FRONT BY TUESDAY. THIS BOUNDARY IS THEN PROGGED TO STALL
AND DISSIPATE SOUTH OF THE REGION DURING THE WED-THU TIME FRAME.
FORECAST UNCERTAINTY REMAINS QUITE HIGH THROUGH THE FIRST HALF OF
THE WEEK...ESPECIALLY GIVEN THE ONGOING POTENTIAL FOR MESOSCALE
CONVECTIVE SYSTEMS IN NW FLOW ALOFT TO IMPACT THE REGION. GIVE
GUIDANCE TRENDS...LOWERED TEMPERATURES SOMEWHAT MON THROUGH
WED...ESPECIALLY ACROSS NORTHERN COUNTIES...AND RAISED POPS TO
ACCOUNT FOR THE POTENTIAL FOR AN UNSETTLED REGIME DURING THAT
PERIOD.

BY LATE IN THE FORECAST PERIOD...MEDIUM RANGE GUIDANCE VARIES FROM
A BUILDING UPPER RIDGE AND A RETURN TO HOT/HUMID CONDITIONS AS
DEPICTED BY THE 0Z EUROPEAN...TO THE APPROACH OF A SHORTWAVE/
ASSOCIATED COLD FRONT FROM THE NW AS DEPICTED BY THE 12Z GFS. THIS
FORECAST WILL FAVOR THE EUROPEAN SCENARIO...WHICH MAINTAINS BETTER
FORECAST CONTINUITY.

&&

.AVIATION /00Z SATURDAY THROUGH WEDNESDAY/...
LARGE OUTFLOW BOUNDARY AHEAD OF CONVECTIVE BAND HEADING SE FROM
THE MIDLANDS INTO THE COASTAL PLAINS WILL CONTINUE PUSHING TWD THE
COAST THROUGH 03Z. MEANWHILE...THE SEABREEZE HAS PUSHED THROUGH
BOTH TERMINALS AND IS GRADUALLY SLIDING INLAND. BOTH BOUNDARIES
WILL INTERACT BUT THERE IS SOME UNCERTAINTY AS TO WHETHER MORE
CONVECTION WILL DEVELOP ALONG IT OR IF THEY WILL CROSS EACH OTHER
WITH NO EFFECTS. IF NOTHING ELSE...THE CONVECTIVE OUTFLOW PUSHING
TWD THE COAST WILL MAKE FOR A BRIEF BOUT OF GUSTY NW WINDS AT BOTH
TERMINALS. IN ADDITION...THE TSTMS MOVING SE TWD THE COAST LOOKS
TO IMPACT KCHS SO HAVE INCLUDED 2 TEMPO HOURS OF +TSRA WITH IFR
VSBY. NO PRECIP IS EXPECTED AT KSAV DURING THE EVENING HOURS SO
HAVE LEFT IT DRY...BUT DID INDICATE THE OUTFLOW WOULD PUSH S
ACROSS THE SAVANNAH RIVER AND PUSH THROUGH THE TERMINAL.

ANY LINGERING PRECIP AFTER 03Z SHOULD DISSIPATE AND/OR MOVE AWAY
FROM THE TERMINALS SHOULD HAVE LEFT A DRY FORECAST GOING THROUGH
THE REST OF THE OVERNIGHT HOURS. THERE IS SOME CONCERN THAT SOME
REMNANTS FROM A POTENT MCS MOVING E THROUGH TN AND NRN PORTIONS OF
THE GULF COAST STATES MAY CONTINUE PROGRESSING TWD THE CAROLINA
COAST DURING THE EARLY MORNING HOURS. CONFIDENCE IS LOW IN THIS
IDEA SO HAVE RUN WITH THE DRY FCST. THE ONLY OTHER CONCERN
OVERNIGHT WILL BE PRE-DAWN MVFR FOG SO HAVE INCLUDED TEMPO GROUPS
JUST BEFORE 13/12Z.

MOSTLY CLEAR SKIES TO START THE DAY TMRW WILL AGAIN GIVE WAY TO A
DECENT CUMULUS CLOUD FIELD BY MIDDAY. ISOLD TO SCATTERED
SHWRS/TSTMS ARE AGAIN POSSIBLE LATE TMRW AFTN...BUT LOW CONFIDENCE
ON TIMING AND COVERAGE PRECLUDES MENTION ATTM. HAVE INCLUDED CB
FOR THE LATE AFTN HOURS.

EXTENDED AVIATION OUTLOOK...ASIDE FROM MAINLY AFTERNOON AND
EVENING SCATTERED SHOWERS AND THUNDERSTORMS WHICH MAY BRIEFLY DROP
VSBYS TO IFR LEVELS...VFR CONDITIONS WILL GENERALLY PREVAIL.
PATCHY FOG MAY REDUCE VSBY TO MVFR DURING EARLY MORNING HOURS.

&&

.MARINE...
ATLC HIGH PRES WILL REMAIN THE DOMINANT FEATURE THROUGH THE FIRST
HALF OF THE WEEKEND...MAINTAINING A PREVAILING SW FLOW OVER THE
WATERS WITH SPEEDS AOB 15 KT AND SEAS AOB 4 FT. SEABREEZE
CIRCULATIONS THROUGH THE REST OF THIS AFTN AND AGAIN ON SAT AFTN
MAY SHIFT WINDS NEAR THE COAST TO A MORE SLY DIRECTION...THEN
WINDS WILL VEER BACK TO SW OR WSW AT NIGHT.

WINDS/SEAS WILL REMAIN WELL BELOW SMALL CRAFT ADVISORY THRESHOLDS
THROUGH THE LATTER HALF OF THE WEEKEND. THE SEA BREEZE
CIRCULATION WILL DOMINATE...AND MODEST NOCTURNAL SURGES OF S/SW
WINDS AS HIGH AS 15 KT WILL REMAIN COMMON. A COLD FRONT WILL PUSH
THROUGH THE WATERS EARLY NEXT WEEK...ALTHOUGH THE TIMING/STRENGTH
OF THIS FROPA REMAIN UNCERTAIN. IF SURFACE HIGH PRESSURE NE OF THE
REGION BECOMES SUFFICIENTLY STRONG...A PERIOD OF SCA CONDITIONS
COULD DEVELOP LATE IN THE FORECAST PERIOD TUE-WED.

&&

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

&&

JPC

HAZARDOUS WEATHER OUTLOOK...UPDATED
NATIONAL WEATHER SERVICE CHARLESTON SC
459 PM EDT FRI JUN 12 2009

AMZ330-350-352-354-GAZ087-088-099>101-114>119-137>141-SCZ040-042>045-
047>051-131030-
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-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-
459 PM EDT FRI JUN 12 2009

...SEVERE THUNDERSTORM WATCH 391 IN EFFECT UNTIL 11 PM EDT THIS
EVENING...

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

.DAY ONE...TONIGHT.

PLEASE LISTEN TO NOAA WEATHER RADIO OR GO TO WEATHER.GOV ON THE
INTERNET FOR MORE INFORMATION ABOUT THE FOLLOWING HAZARDS.

   SEVERE THUNDERSTORM WATCH.

.DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY.

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.SPOTTER INFORMATION STATEMENT...

WEATHER SPOTTERS ARE ENCOURAGED TO REPORT SIGNIFICANT WEATHER
CONDITIONS ACCORDING TO STANDARD OPERATING PROCEDURES.

AMZ374-131030-
WATERS FROM SAVANNAH GA TO ALTAMAHA SOUND GA EXTENDING FROM 20 TO
60 NM-
459 PM EDT FRI JUN 12 2009

THIS HAZARDOUS WEATHER OUTLOOK IS FOR ATLANTIC COASTAL WATERS.

.DAY ONE...TONIGHT.

SEVERE THUNDERSTORMS...SHOWERS AND THUNDERSTORMS WILL AGAIN
DEVELOP ACROSS THE AREA THROUGH EVENING. SOME OF THE STORMS COULD
BE SEVERE...PRODUCING DAMAGING WINDS AND LARGE HAIL.

.DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY.

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.SPOTTER INFORMATION STATEMENT...

WEATHER SPOTTERS ARE ENCOURAGED TO REPORT SIGNIFICANT WEATHER
CONDITIONS ACCORDING TO STANDARD OPERATING PROCEDURES.

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SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE CHARLESTON SC
955 PM EDT FRI JUN 12 2009

SCZ047-048-051-130230-
BEAUFORT-COASTAL JASPER-INLAND JASPER-
955 PM EDT FRI JUN 12 2009

...STRONG THUNDERSTORMS WILL IMPACT EAST CENTRAL JASPER AND CENTRAL
BEAUFORT COUNTIES THROUGH 1030 PM EDT...

AT 955 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
STRONG THUNDERSTORM CAPABLE OF PRODUCING PEA SIZE HAIL...AND GUSTY
WINDS OF 30 TO 40 MPH.  THIS STORM WAS LOCATED NEAR CHELSEA...OR
ABOUT 10 MILES SOUTHEAST OF RIDGELAND...MOVING EAST AT 20 MPH.

AREAS IN AND AROUND CALAWASSIE ISLAND...FOLLY FIELD...HILTON HEAD
AIRPORT...JASPER...LEMON ISLAND...PARRIS ISLAND...PORT ROYAL AND ROSE
HILL WILL BE IMPACTED THROUGH 1030 PM EDT.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

PLEASE CONTACT THE NATIONAL WEATHER SERVICE IN CHARLESTON TOLL FREE
AT 1-888-383-2024 IF YOU OBSERVE SEVERE WEATHER SUCH AS HAIL...DOWNED
TREES...LIMBS AND POWER LINES.

&&

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE CHARLESTON SC
1011 PM EDT FRI JUN 12 2009

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0856 PM     TSTM WND DMG     JOHNS ISLAND            32.72N 80.07W
06/12/2009                   CHARLESTON         SC   LAW ENFORCEMENT

            TREE DOWN ALONG RIVER ROAD.

&&

VB