Severe Thunderstorm Warning 99, NWS Charleston, SC

000 
WWUS52 KCHS 291821
SVSCHS

SEVERE WEATHER STATEMENT
NATIONAL WEATHER SERVICE CHARLESTON SC
221 PM EDT FRI MAY 29 2009

GAC031-165-291831-
/O.CAN.KCHS.SV.W.0099.000000T0000Z-090529T1845Z/
BULLOCH GA-JENKINS GA-
221 PM EDT FRI MAY 29 2009

...THE SEVERE THUNDERSTORM WARNING FOR SOUTHEASTERN JENKINS AND NORTH
CENTRAL BULLOCH COUNTIES HAS BEEN CANCELLED...

TO REPORT SEVERE WEATHER SUCH AS HAIL...DOWNED TREES...LIMBS...AND
POWER LINES...PLEASE CONTACT THE CHARLESTON NATIONAL WEATHER SERVICE
TOLL FREE AT 1-888-383-2024 OR EMAIL YOUR REPORTS TO
CHS.SKYWARN@NOAA.GOV.

LAT...LON 3260 8175 3269 8179 3279 8146 3258 8142
TIME...MOT...LOC 1821Z 275DEG 17KT 3263 8171

$$

GAC251-291845-
/O.CON.KCHS.SV.W.0099.000000T0000Z-090529T1845Z/
SCREVEN GA-
221 PM EDT FRI MAY 29 2009

...A SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT UNTIL 245 PM EDT
FOR SOUTHERN SCREVEN COUNTY...

AT 220 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR CONTINUED TO
INDICATE A SEVERE THUNDERSTORM CAPABLE OF PRODUCING PENNY SIZE
HAIL...AND DAMAGING WINDS IN EXCESS OF 60 MPH.  THIS STORM WAS
LOCATED NEAR GOLOID...OR ABOUT 9 MILES NORTHEAST OF MIDDLEGROUND...
MOVING EAST AT 20 MPH.

AT 200 PM EDT...LAW ENFORCEMENT REPORTED PEA SIZED HAIL IN ROCKY 
FORD.

SOME LOCATIONS IN OR NEAR THE PATH OF THIS STORM INCLUDE...ALTMAN...
CAPTOLO...HUNTERS AND NEWINGTON.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

EXCESSIVE LIGHTNING IS OCCURRING WITH THIS THUNDERSTORM. IF
OUTDOORS... AVOID OPEN SPACES AND REMAIN LOW...KEEPING YOUR DISTANCE
FROM TALL OBJECTS SUCH AS TREES AND UTILITY POLES. IF INDOORS...STAY
AWAY FROM WINDOWS AND PLUMBING. ELECTRICAL APPLIANCES SHOULD BE
UNPLUGGED UNTIL THE THUNDERSTORM IS NO LONGER A THREAT.

TO REPORT SEVERE WEATHER SUCH AS HAIL...DOWNED TREES...LIMBS...AND
POWER LINES...PLEASE CONTACT THE CHARLESTON NATIONAL WEATHER SERVICE
TOLL FREE AT 1-888-383-2024 OR EMAIL YOUR REPORTS TO
CHS.SKYWARN@NOAA.GOV.

&&

LAT...LON 3260 8175 3269 8179 3279 8146 3258 8142
TIME...MOT...LOC 1821Z 275DEG 17KT 3263 8171

$$


33

000 
WWUS52 KCHS 291841
SVSCHS

SEVERE WEATHER STATEMENT
NATIONAL WEATHER SERVICE CHARLESTON SC
241 PM EDT FRI MAY 29 2009

GAC251-291851-
/O.EXP.KCHS.SV.W.0099.000000T0000Z-090529T1845Z/
SCREVEN GA-
241 PM EDT FRI MAY 29 2009

...THE SEVERE THUNDERSTORM WARNING FOR SOUTHERN SCREVEN COUNTY WILL
EXPIRE AT 245 PM EDT...

AT 240 PM EDT...RADAR INDICATED THAT THE THUNDERSTORM WHICH PROMPTED
THE WARNING HAD WEAKENED...THUS THE SEVERE THUNDERSTORM WARNING HAS
BEEN ALLOWED TO EXPIRE.

TO REPORT SEVERE WEATHER SUCH AS HAIL...DOWNED TREES...LIMBS...AND
POWER LINES...PLEASE CONTACT THE CHARLESTON NATIONAL WEATHER SERVICE
TOLL FREE AT 1-888-383-2024 OR EMAIL YOUR REPORTS TO
CHS.SKYWARN@NOAA.GOV.

A SEVERE THUNDERSTORM WATCH REMAINS IN EFFECT UNTIL 1000 PM EDT 
FRIDAY EVENING FOR SOUTHEAST GEORGIA AND SOUTHEAST SOUTH CAROLINA.

LAT...LON 3260 8175 3269 8179 3279 8146 3258 8142
TIME...MOT...LOC 1841Z 275DEG 17KT 3262 8160

$$

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
153 PM EDT FRI MAY 29 2009

.SYNOPSIS...
A COLD FRONT WILL APPROACH FROM THE NW LATE TODAY THEN MOVE THROUGH
THE AREA TONIGHT. ATLC HIGH PRES WILL THEN REBUILD OVER THE SOUTHEAST
UNITED STATES OVER THE WEEKEND AND REMAIN THE DOMINANT WEATHER FEATURE
THROUGH THE UPCOMING WEEK.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
A FAIRLY MOIST AIRMASS CONTINUES ACROSS THE AREA EAST OF A COLD
FRONT DRAPED FROM THE SC UPSTATE ACROSS CENTRAL GA INTO THE FL
PANHANDLE. THIS FEATURE WILL DRIFT EAST THROUGH EARLY THIS EVENING
BEING DRIVEN BY A STRONG SHORTWAVE NOW OVER THE SOUTHERN
APPALACHIANS. A PATCH OF STRATUS IN SOUTHEAST GA HAS TEMPORARILY
STALLED WARMING...HOWEVER IT SHOULD DISSIPATE FAIRLY QUICKLY
DURING THE NEXT TWO HOURS AND WILL HAVE CREATED SOME DIFFERENTIAL
HEATING BOUNDARIES. MUCH OF THE GUIDANCE CONTINUES TO HOLD OFF ON
SIGNIFICANT CONVECTIVE DEVELOPMENT ALONG THE SEABREEZE EARLY THIS
AFTERNOON. BY MID TO LATE AFTERNOON...WITH THE COLD FRONT SHIFTING
INTO WESTERN ZONES AROUND PEAK HEATING...SCATTERED THUNDERSTORMS
SHOULD DEVELOP.

THE NSSL WRF IS AN OUTLIER WITH AN ORGANIZED CLUSTER OF STORMS
MOVING INTO THE AREA FROM THE WEST LATE THIS AFTERNOON THROUGH THE
EARLY EVENING. DESPITE IT BEING AN OUTLIER...IT OFTEN PERFORMS
VERY WELL IN THESE SETUPS INVOLVING MESOSCALE CONVECTIVE
PROCESSES. THE CONVECTIVE CHECKLIST FROM THE 12Z RAOB FROM CHS
INDICATES AN AIRMASS FAIRLY WELL PRIMED FOR STRONG TO SEVERE
CONVECTION. INSTABILITY PARAMETERS SHOW THE POTENTIAL FOR STRONG
UPDRAFTS WHILE SHEAR VALUES ARE MARGINAL. A GOOD AMOUNT OF LOW-
LEVEL DRY AIR SHOWS THE POTENTIAL FOR DAMAGING WIND TO BE THE MAIN
THREAT. OVERALL...CURRENT THINKING IS SIMILAR TO THAT OF THE
PREVIOUS SHIFT IN THAT THE SEABREEZE WILL STRUGGLE TO LIGHT UP DUE
TO A CONSIDERABLE CAP...BUT AN ACTIVE LATE AFTERNOON AND EVENING
WILL OCCUR ONCE THE CAP BREAKS AND BOUNDARIES INTERACT. NO CHANGES
TO MOST FORECAST GRIDS BUT DID ADD MENTION OF SEVERE THUNDERSTORMS
TO THE WEATHER FORECAST.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 AM SATURDAY/...
RECENT MODEL TRENDS SHOW SIGNALS OF STRONG TO SEVERE NEAR-COASTAL
CONVECTION LINGERING INTO THE EARLY EVENING HOURS AS THE 60-70 KT
UPPER JET SEGMENTS MAKE A RUN AT PHASING OVER THE EASTERN HALF OF
OUR FORECAST AREA. THE WRF AND GEM MODELS INDICATE SOME VERY
INTERESTING MODEL UNDULATIONS OF CONVECTIVE FIELDS ALONG THE
GEORGIA COAST WHICH COULD INDICATE A TIP THAT ORGANIZED STORMS MAY
TRY TO FIRE AND SURGE OFF THE COAST PROMOTING MARINE HAZARDS. AS A
TREND...WE INCREASED EVENING POPS TO CHANCE RANGE FROM DARIEN TO
SAVANNAH TO CHARLESTON BUT STILL MANY TIMING FACTORS HAVE TO COME
TOGETHER FOR AN EARLY EVENING EVENT.

THE FRONT WILL BE SAGGING THROUGH THE REGION LATE WITH CLOUDS
THINNING OUT AFTER MIDNIGHT. SURFACE WINDS WILL GRADUALLY BE
VEERING TO A LIGHT NNW COMPONENT LATE OVER THE NORTHERN HALF OF THE
FORECAST AREA. IF MANY AREAS SEE RNFL AT SOME POINT TODAY...SOME
FOG IS POSSIBLE IN THE FRONTAL ZONE OVERNIGHT. CONFIDENCE IS NOT
THERE YET TO INCLUDE IN OUR FORECAST.

&&

.LONG TERM /SATURDAY THROUGH THURSDAY/...
GUIDANCE IS IN GOOD AGREEMENT WITH A PROGRESSIVE COLD FRONTAL
PASSAGE FRIDAY NIGHT...AND ATLANTIC HIGH PRESSURE THEN REBUILDING
OVER THE FORECAST AREA OVER THE WEEKEND. HIGH PRESSURE IS THEN
EXPECTED TO REMAIN THE DOMINANT WEATHER FEATURE THROUGH MUCH OF THE
UPCOMING WORK WEEK.

DEEP MOISTURE IS EXPECTED TO SHIFT OFFSHORE LATE FRIDAY NIGHT...AND
THIS SHOULD LIMIT THE POTENTIAL FOR ANY SHOWER/THUNDERSTORM ACTIVITY
SATURDAY...SO WILL KEEP THE FORECAST RAIN FREE. WITH LACK OF DEEP
MOISTURE RETURN...WEST-SOUTHWESTERLY DOWNSLOPE FLOW...AND LACK OF
ANY SIGNIFICANT FORCING MECHANISM ASIDE FROM THE SEA BREEZE...EXPECT
RAIN FREE CONDITIONS TO CONTINUE SATURDAY NIGHT THROUGH SUNDAY NIGHT.

MODEL SOLUTIONS SUGGEST THAT A WEAKENING COLD FRONT WILL SLIDE
SOUTHWARD INTO THE FORECAST AREA LATE SUNDAY NIGHT AND
MONDAY...BRINGING WITH IT SLIGHTLY DEEPER MOISTURE AND ANOTHER
FOCUSING MECHANISM IN ADDITION TO THE AFTERNOON SEA BREEZE. AT THIS
POINT AM NOT ANTICIPATING MUCH IN THE WAY OF SHOWER/THUNDERSTORM
COVERAGE...BUT SHOULD SEE ENOUGH TO JUSTIFY SLIGHT CHANCE POPS
ACROSS PRIMARILY NORTHWEST ZONES MONDAY AFTERNOON.

THE WEAKENING FRONTAL BOUNDARY WILL DISSIPATE MONDAY NIGHT...WITH
ATLANTIC HIGH PRESSURE THEN REBUILDING OVER THE REGION TUESDAY
THROUGH WEDNESDAY. NOT TOO EXCITED ABOUT SHOWER/THUNDERSTORM CHANCES
EACH AFTERNOON...BUT CAN/T RULE OUT AN ISOLATED SHOWER/THUNDERSTORM
ACROSS FAR WESTERN ZONES IN CLOSER PROXIMITY TO A DEVELOPING LEE
SIDE TROUGH. THEREFORE...WILL CARRY SLIGHT CHANCE POPS HERE WITH
RAIN FREE CONDITIONS FOR COASTAL ZONES.

GUIDANCE IS IN FAIRLY GOOD AGREEMENT BREAKING DOWN THE ATLANTIC
RIDGE THURSDAY AS A COLD FRONT BEGINS TO APPROACH THE REGION FROM
THE WEST. THE SOUTHERLY FLOW IN ADVANCE OF THE COLD FRONT WILL ALLOW
DEEP MOISTURE TO BEGIN INCREASING OVER THE AREA FROM BOTH THE
ATLANTIC AND GULF OF MEXICO...SO WILL CARRY CHANCE POPS MOST AREAS.

TEMPERATURES ARE EXPECTED TO RUN SLIGHTLY ABOVE CLIMATOLOGY
THROUGHOUT THE EXTENDED PERIODS.

&&

.AVIATION /18Z FRIDAY THROUGH WEDNESDAY/...
HAVE MAINTAINED VFR CONDITIONS FOR KCHS AND KSAV THROUGH THE 18Z TAF
PERIOD. INCLUDED A CB GROUP FOR KCHS PRIOR TO 21Z AS RADAR SHOWS
DEVELOPMENT ALONG THE SEABREEZE. YET CONFIDENCE REMAINS LOW THAT KCHS
WILL BE AFFECTED...THUS WILL KEEP SHRA OUT OF TAFS FOR NOW. ADDITIONAL
ACTIVITY IS EXPECTED AS A COLD FRONT APPROACHES THE AREA FROM THE
WEST LATER THIS AFTERNOON INTO THE EVENING FOR BOTH TERMINALS. KEPT
CB GROUPS WHILE INCLUDING VCSH AS INSTABILITY LOOKS FAIRLY
IMPRESSIVE FOR THUNDERSTORM DEVELOPMENT AFTER 21Z. MODELS REMAIN
INCONSISTENT IN TIMING OF CONVECTION THUS WILL CONTINUE TO MONITOR
RADAR TRENDS AND AMEND TAFS IF NEEDED...ESPECIALLY FOR KSAV AS
INTERACTIONS BETWEEN THE GULF COAST SEA BREEZE AND A PINNED ATLC SEA
BREEZE AID THUNDERSTORM DEVELOPMENT. GUIDANCE ALSO REMAINS
INCONSISTENT REGARDING FOG FORMATION EARLY SATURDAY MORNING. YET
WITH SKIES CLEARING...RELATIVELY LIGHT WINDS AND LINGERING LOW LEVEL
MOISTURE...CANNOT RULE OUT SOME MVFR VISIBILITIES/CEILINGS AFTER 08Z.
WILL REEVALUATE FOG POTENTIAL FOR THE NEXT TAF PERIOD.

EXTENDED AVIATION OUTLOOK...VFR CONDITIONS EXPECTED SAT THROUGH
TUE.

&&

.MARINE...
LOW LEVEL TROF WILL RESIDE INLAND TODAY AND A SYNOPTIC SW FLOW
WILL RESIDE OVER THE WATERS THROUGH THIS EVENING. NEAR SHORE...
THERE MAY BE A BIT A W COMPONENT THIS MORNING AND A SOUTHERLY
DIRECTION POST SEA BREEZE. SPEEDS WILL COME DOWN FROM 10-15 KT
EARLY TO NEAR 10 KT BEFORE A LATE DAY INCREASE BACK INTO THE
10-15 KT RANGE. SEAS MAINLY 2-3 FT. TONIGHT...A COLD FRONT WILL BE
MAKING SOME LATE NIGHT HEADWAY INTO THE WATERS AND OTHER THAN THE
LIGHT LATE NIGHT WIND SHIFT...WINDS AND SEAS ON THE LIGHT SIDE. AS
MENTIONED IN THE SHORT TERM DISCUSSION... MARINE INTERESTS SHOULD
KEEP AN EYE OUT FOR A POTENTIAL OF SOME STRONG EVENING TSTMS.

ATLANTIC HIGH PRESSURE WILL REBUILD OVER THE SOUTHEAST UNITED STATES
SATURDAY THROUGH TUESDAY...RESULTING IN TRANQUIL CONDITIONS OVER THE
SOUTH CAROLINA AND GEORGIA COASTAL WATERS. WINDS ARE EXPECTED TO
REMAIN AT OR BELOW 15 KNOTS...WITH SEAS AT OR BELOW 3 FEET SATURDAY
THROUGH TUESDAY.

&&

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

&&

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE CHARLESTON SC
415 AM EDT FRI MAY 29 2009

AMZ330-350-352-354-374-GAZ087-088-099>101-114>119-137>141-SCZ040-
042>045-047>051-300900-
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-
415 AM EDT FRI MAY 29 2009

...SLIGHT RISK OF SEVERE THUNDERSTORMS 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 WEATHER...A COLD FRONT WILL APPROACH THE REGION FROM THE
NORTHWEST LATE TODAY INTO THIS EVENING. IN ADVANCE OF THE FRONT...
SCATTERED THUNDERSTORMS ARE EXPECTED TO DEVELOP THIS AFTERNOON INTO
THIS EVENING AND MOVE TOWARD THE COAST. HIGH TEMPERATURES NEAR 90
DEGREES COMBINED WITH A MOIST AND UNSTABLE AIR MASS WILL SET THE
STAGE FOR THE POTENTIAL OF A FEW SEVERE THUNDERSTORMS. THE MAIN
HAZARDS WILL BE LARGE HAIL AND DAMAGING WIND GUSTS. THE EXPECTED
TIME FRAME FOR SEVERE WEATHER WILL BE FROM AROUND 2 PM TO MIDNIGHT
TONIGHT.

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

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION MAY BE NEEDED THIS AFTERNOON AND EVENING.

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE CHARLESTON SC
125 PM EDT FRI MAY 29 2009

GAZ087-088-100-291800-
BULLOCH-JENKINS-SCREVEN-
125 PM EDT FRI MAY 29 2009

...STRONG THUNDERSTORMS WILL IMPACT SOUTHWESTERN SCREVEN...SOUTHERN
JENKINS AND NORTHWESTERN BULLOCH COUNTIES THROUGH 200 PM EDT...

AT 124 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
STRONG THUNDERSTORM CAPABLE OF PRODUCING 1/2 INCH HAIL...AND GUSTY
WINDS OF 35 TO 45 MPH.  THIS STORM WAS LOCATED NEAR FOUR POINTS...OR
ABOUT 12 MILES SOUTHWEST OF MILLEN...MOVING EAST AT 15 MPH.

AREAS IN AND AROUND BUTTS...DOVER...ROCKY FORD...SCARBORO AND
WOODCLIFF WILL BE IMPACTED THROUGH 200 PM EDT.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

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.

&&

33

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE CHARLESTON SC
146 PM EDT FRI MAY 29 2009

GAZ087-088-100-291815-
BULLOCH-JENKINS-SCREVEN-
146 PM EDT FRI MAY 29 2009

...STRONG THUNDERSTORMS WILL IMPACT WEST CENTRAL SCREVEN...SOUTHERN
JENKINS AND NORTHWESTERN BULLOCH COUNTIES THROUGH 215 PM EDT...

AT 145 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
STRONG THUNDERSTORM CAPABLE OF PRODUCING 1/2 INCH HAIL...AND STRONG
WINDS OF 45 TO 55 MPH. THIS STORM WAS LOCATED NEAR FOUR POINTS...OR
ABOUT 10 MILES SOUTH OF MILLEN...MOVING EAST AT 15 MPH.

AREAS IN AND AROUND BUTTS...DOVER...FOUR POINTS...ROCKY
FORD...SCARBORO AND WOODCLIFF WILL BE IMPACTED THROUGH 215 PM EDT.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

HAVE AN ACTION PLAN READY IN THE EVENT THIS STORM STRENGTHENS OR A
WARNING IS ISSUED. CONTINUE TO MONITOR NOAA WEATHER RADIO ALL HAZARDS
FOR THE LATEST WEATHER INFORMATION.

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.

&&

33