...PENNSYLVANIA WEATHER EMERGENCY PREPAREDNESS WEEK...

THIS IS THE FOURTH OF A FIVE PART SERIES ON SEVERE WEATHER SAFETY 
WHICH WILL RUN EACH DAY DURING PENNSYLVANIA/S WEATHER EMERGENCY 
PREPAREDNESS WEEK. 

...RIVER FLOODING AND RIVER FLOOD SAFETY. 

PENNSYLVANIA HAS SCENIC RIVER SYSTEMS. HOWEVER...ON OCCASION...
THESE RIVERS CAN BECOME DESTRUCTIVE...AND EVEN DEADLY.  SIGNIFICANT 
RIVER FLOODS HAVE OCCURRED THROUGHOUT THE YEARS, MOST NOTABLY IN 
1936...1972...1996...1999...2004...2005...AND MOST RECENTLY...
2006 DUE TO THE TORRENTIAL RAINFALL FROM THE REMNANTS OF TROPICAL 
SYSTEMS.

WHAT CAUSES RIVER FLOODS?
GENERALLY...PROLONGED PERIODS OF HEAVY RAINFALL...SOMETIMES
COMBINED WITH EXTENSIVE SNOWMELT...OVER A LARGE AREAS WILL CAUSE 
THE RIVERS TO SWELL AND OCCASIONALLY FLOOD. THIS IS ESPECIALLY 
TRUE IN LATE WINTER AND SPRING WHEN THE SNOWPACK BEGINS TO MELT.
IF THE SNOW MELTS QUICKLY AND IS COMBINED WITH HEAVY RAINFALL...
MAJOR FLOODING COULD RESULT SUCH AS THE FLOODS THAT OCCURRED 
IN JANUARY 1996. MASSIVE FLOODING IN THE MID ATLANTIC REGION SELDOM 
RESULTS FROM SNOWMELT ALONE...GENERALLY RAIN IS NEEDED AS WELL.

RIVER FLOODING CAN RESULT IN WIDESPREAD PROPERTY DAMAGE AND MAY 
RESULT IN LOSS OF LIFE.  MORE THAN 50 PERCENT OF THE DEATHS 
ASSOCIATED WITH FLOODING ARE AUTOMOBILE RELATED.

RIVERS CAN FLOOD ANYTIME OF THE YEAR.  IN WINTER AND EARLY
SPRING...RAPID MELTING OF A DEEP SNOWPACK WITH HEAVY RAIN CAN BE THE
CULPRIT.  IN SUMMER...COMPLEXES OF SLOW MOVING THUNDERSTORMS CAN
CAUSE THE RIVERS TO FLOOD.  IN LATE SUMMER AND FALL...TROPICAL STORMS
AND HURRICANES ARE THE BIGGEST THREAT FOR RIVER FLOODING.

TIDAL FLOODING GENERALLY OCCURS WHEN AN ONSHORE FLOW COINCIDES WITH
HIGH ASTRONOMICAL TIDES ASSOCIATED WITH A NEW MOON OR FULL MOON. BACK
BAY AND OCEAN FRONT FLOODING IS MADE WORSE BY HEAVY RAIN AND WAVE
ACTION. IN ADDITION, BACK BAY FLOODING CAN BE MORE SEVERE THAN OCEAN
FRONT FLOODING IF A STORM MOVES SLOWLY UP THE COAST THROUGH SEVERAL
TIDE CYCLES. TIDAL FLOODING OCCURS NEAR THE NEW JERSEY COAST, BUT
ALSO IN SOUTHERN PORTIONS OF NEW JERSEY AND IN THE DELAWARE BAY AND
DELAWARE RIVER AS FAR NORTH AS TRENTON. 

WHAT DOES A FLOOD WATCH MEAN?
A FLOOD WATCH MEANS THERE IS POTENTIAL FOR FLOODING TO OCCUR...NOT
THAT RIVER FLOODING IS OCCURRING.  THE WATCH IS TYPICALLY ISSUED FOR
ONE OR MORE POINTS ALONG THE RIVER COUNTIES AT A TIME...AND IDEALLY
IS ISSUED 12 TO 24 HOURS BEFORE FLOODING IS EXPECTED.  THIS WAY YOU
WILL HAVE ENOUGH TIME TO PREPARE.

WHAT YOU SHOULD DO WHEN A FLOOD WATCH IS ISSUED?
GO ABOUT YOUR NORMAL ACTIVITIES...BUT MAKE PERIODIC CHECKS OF NOAA 
WEATHER RADIO OR OTHER MEDIA OUTLETS FOR UPDATES AND POSSIBLE FLOOD 
WARNINGS.  GET READY TO MOVE YOUR PERSONAL PROPERTY OUT OF THE AREAS 
THAT ARE KNOWN TO FLOOD.

IF YOU LIVE OR WORK IN AN AREA WHICH IS PRONE TO FLOODING...HAVE A
SAFE EVACUATION ROUTE TO USE IF FLOODING OCCURS.  MAKE SURE EVERYONE 
IN YOUR HOME OR OFFICE KNOWS WHERE TO GO IF FLOODING OCCURS. 
HAVE A BATTERY OPERATED RADIO...AND SEVERAL WORKING FLASHLIGHTS 
AVAILABLE.  TAKE PRECAUTIONS TO SECURE YOUR PROPERTY.

WHAT DOES A RIVER FLOOD WARNING MEAN?
A RIVER FLOOD WARNING MEANS THAT RIVER LEVELS WILL EXCEED FLOOD
STAGE ON CERTAIN POINTS ALONG THE LARGER RIVERS...LIKE THE 
DELAWARE...LEHIGH...AND SCHUYLKILL RIVERS.  RIVER FLOODS TAKE 
LONGER TO DEVELOP THAN FLASH FLOODING...SO THEY MAY NOT POSE AS MUCH 
THREAT TO LIFE...BUT CAN TAKE A MUCH LARGER TOLL ON PROPERTY.

WHAT YOU SHOULD DO WHEN A RIVER FLOOD WARNING IS ISSUED?
IF YOU LIVE IN THE FLOOD PLAIN...BE PREPARED TO EVACUATE IF ORDERED
TO DO SO.  MAKE SURE YOU HAVE ALL NECESSARY ITEMS IN THE EVENT THAT 
YOU CANNOT RETURN HOME FOR SEVERAL DAYS.  MAKE ARRANGEMENTS TO 
PROTECT YOUR PROPERTY BY MOVING YOUR VALUABLES TO HIGHER GROUND...OR 
AN UPPER LEVEL OF YOUR HOME.  LISTEN FOR RIVER LEVEL FORECASTS THAT 
PREDICT FLOODING.  OBEY EVACUATION ORDERS FROM EMERGENCY MANAGEMENT 
OR LOCAL LAW ENFORCEMENT OFFICIALS.

ONE OF THE BEST WAYS TO CHECK EXISTING AND FORECAST CONDITIONS ON 
WATERWAYS THROUGHOUT OUR REGION IS TO MONITOR THE ADVANCED 
HYDROLOGIC PREDICTION SERVICE /AHPS/ WHICH IS ALSO AVAILABLE ON THE 
NWS MOUNT HOLLY WEB SITE. JUST CLICK THE AHPS ICON ON THE LEFT HAND 
MENU.

FOR ADDITIONAL INFORMATION ON RIVER FLOODS...FLASH FLOODS...AND THE
"TURN AROUND DON'T DROWN" CAMPAIGN, PLEASE VISIT THE NWS FLOOD 
AWARENESS WEBSITE AT WWW.FLOODSAFETY.NOAA.GOV. MARCH 10 TO 14 IS 
NATIONAL FLOOD SAFETY AWARENESS WEEK. 

THE WEATHER SAFETY TOPIC FOR FRIDAY WILL BE...
SKYWARN SEVERE WEATHER SPOTTERS.

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