National Weather Service Raw Text Product

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NOUS42 KGSP 090658
PNSGSP
NCZ033>037-048>059-062>072-082-SCZ001>014-019-100000-

PUBLIC INFORMATION STATEMENT
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
200 AM EST FRI MAR 9 2012

...PUBLIC INFORMATION STATEMENT...

THIS IS SEVERE WEATHER AWARENESS WEEK IN THE CAROLINAS. FAMILIES AND 
INDIVIDUALS...AS WELL AS EMPLOYERS AND OTHER ORGANIZATIONS...ARE 
URGED TO USE THE INFORMATION PROVIDED THIS WEEK TO DEVISE THEIR OWN 
SEVERE WEATHER SAFETY PLANS. IF YOU ALREADY HAVE A PLAN IN PLACE... 
YOU ARE ENCOURAGED TO USE THIS OPPORTUNITY TO REVIEW YOUR PROCEDURES 
AND PERFORM DRILLS AND EXERCISES. 2011 WAS AN UNUSUALLY ACTIVE YEAR 
FOR SEVERE WEATHER ACROSS THE WESTERN CAROLINAS...WITH MULTIPLE 
STRONG TORNADOES REPORTED...AND NUMEROUS STRONG DOWNBURST EVENTS. 
THERE ARE NO GUARANTEES THAT 2012 WILL BE LESS ACTIVE...OR WILL NOT 
BE EVEN MORE ACTIVE THAN 2011. THE TIME TO PREPARE FOR VIOLENT 
WEATHER IS RIGHT NOW.

TODAY...OUR FOCUS IS ON FLASH FLOODING. FLOODING IS THE LEADING 
CAUSE OF WEATHER RELATED FATALITIES IN THE COUNTRY. THERE ARE 2 
BASIC TYPES OF FLOODING...FLASH FLOODING AND GENERAL FLOODING. THE 
MAIN DIFFERENCE IN THE TWO IS THE TIME IN WHICH IT TAKES FLOODING TO 
DEVELOP IN RESPONSE TO EXCESSIVE RAINFALL. GENERAL FLOODING USUALLY 
DEVELOPS AFTER AN EXTENDED PERIOD OF WIDESPREAD MODERATE TO HEAVY 
RAIN. RIVERS AND STREAMS RISE GRADUALLY...TAKING HOURS...OR IN THE 
CASE OF LARGE RIVERS...EVEN A DAY OR MORE TO REACH FLOOD STAGE.  

FLASH FLOODS DEVELOP RAPIDLY...HENCE THE NAME. THEY ARE USUALLY THE 
RESULT OF AN EXCESSIVE AMOUNT OF RAIN FALLING IN A VERY SHORT PERIOD 
OF TIME. THIS IS USUALLY CAUSED BY SLOW-MOVING OR NEARLY STATIONARY 
THUNDERSTORMS PRODUCING VERY HEAVY RAINFALL IN A LOCALIZED AREA... 
OR FROM A SERIES THUNDERSTORMS MOVING ONE AFTER THE OTHER OVER THE 
SAME LOCATION. FLASH FLOODING CAN DEVELOP IN A MATTER OF MINUTES. 
THEREFORE...IT IS THE MORE DANGEROUS TYPE OF FLOODING.   

FLASH FLOODING IS ESPECIALLY DANGEROUS IN AND IMMEDIATELY DOWNSTREAM 
OF MOUNTAINOUS AREAS. WHEN RELATIVELY SMALL STREAMS ARE SURROUNDED 
BY STEEP TERRAIN...EXCESSIVE RAIN FALLING ON THE SLOPES IS CHANNELED 
INTO THE NARROW STREAM BELOW...WHICH CANNOT HANDLE THE ADDITIONAL 
WATER. THIS SOMETIMES RESULTS IN A WALL OF WATER THAT RUSHES RAPIDLY 
DOWNSTREAM...DESTROYING ANYTHING IN ITS PATH. IN ADDITION TO 
FLOODING...A COMBINATION OF EXCESSIVE RAINFALL AND OTHER NATURAL 
EVENTS CAN LEAD TO MUDSLIDES AND LANDSLIDES IN MOUNTAINOUS AREAS. 
THESE PHENOMENA ARE CAPABLE OF CAUSING DEVASTATING DAMAGE.  

URBAN AREAS ARE ALSO SUSCEPTIBLE TO SEVERE FLASH FLOODING. IN THESE 
SITUATIONS...DUE TO THE PRESENCE OF ASPHALT...CONCRETE...AND OTHER 
MAN-MADE MATERIALS THAT CANNOT ABSORB WATER...EXCESSIVE RAINFALL HAS 
NOWHERE TO GO...OVERFLOWING STORM SEWERS AND CULVERTS AND COVERING 
STREETS WITH SWIFTLY MOVING WATER. ONE OF THE MAIN DANGERS 
ASSOCIATED WITH URBAN FLOODING IS THAT OF CHILDREN PLAYING AROUND 
STORM SEWERS. IN THE PAST...CHILDREN HAVE DROWNED AFTER BEING SWEPT 
INTO THE SEWER BY RUSHING WATER. THE CITY OF CHARLOTTE IS ESPECIALLY 
SUSCEPTIBLE TO THIS TYPE OF FLOODING. THE CITY TYPICALLY EXPERIENCES 
SEVERAL FLASH FLOOD EVENTS EVERY YEAR. ONE SEVERE FLASH FLOOD 
OCCURRED ON AUGUST 5 OF LAST YEAR. NUMEROUS SMALL STREAMS OVERFLOWED 
AND SEVERE URBAN FLOODING DEVELOPED WHEN 4 TO 7 INCHES OF RAIN FELL 
OVER THE METRO AREA IN ONLY A 3 HOUR PERIOD. NUMEROUS SWIFT WATER 
RESCUES WERE PERFORMED AND 2 PEOPLE DROWNED IN FLOOD WATER...WHILE 
MILLIONS OF DOLLARS IN DAMAGE OCCURRED.    

MOST PEOPLE WHO DIE AS A RESULT OF FLOODING DO SO WHEN THEY DRIVE 
THEIR VEHICLES OVER FLOODED ROADS. WATER CAN BE DECEPTIVELY 
POWERFUL. TWO FEET OF FAST-MOVING WATER WILL CAUSE MOST VEHICLES TO 
FLOAT.  ONCE YOUR VEHICLE SUCCUMBS TO THE WATER...IT WILL LIKELY 
CARRY THE VEHICLE AND YOU INTO THE FLOODING STREAM...AT WHICH TIME 
YOU WILL EITHER HAVE TO BE RESCUED OR YOU WILL DROWN. NEVER DRIVE 
ACROSS ROADS COVERED WITH MOVING WATER. IT IS VERY EASY TO MISJUDGE 
THE DEPTH OF THE WATER AND TO OVERESTIMATE THE ABILITY OF YOUR 
VEHICLE TO DRIVE THROUGH IT.

PEOPLE WHO LIVE ALONG CREEKS AND STREAMS... ESPECIALLY THOSE PRONE 
TO FLOODING...SHOULD MAINTAIN VIGILANCE DURING TIMES OF HEAVY 
RAINFALL. IF A FLASH FLOOD WARNING IS ISSUED...OR FLOODING IS 
OBSERVED...SEEK HIGHER GROUND IMMEDIATELY. PEOPLE LIVING OR CAMPING 
ALONG STREAMS IN COMPLEX TERRAIN SHOULD REMEMBER THAT IT DOES NOT 
HAVE TO BE RAINING WHERE YOU ARE FOR SEVERE FLASH FLOODING TO 
DEVELOP. IF YOU HEAR PERSISTENT THUNDER UPSTREAM OF YOU...REMAIN 
ALERT FOR RAPIDLY RISING WATER. PEOPLE PLANNING TO CAMP ALONG 
MOUNTAIN STREAMS SHOULD BRING A NOAA WEATHER RADIO OR OTHER MEANS OF 
RECEIVING UP-TO-DATE WEATHER INFORMATION.   

FOR MORE INFORMATION ON WEATHER SAFETY...VISIT OUR WEBSITE AT 
WEATHER.GOV/GSP.

$$ 
LANE