Thursday, February 26, 2009

Rain And Thunderstorms On The Way....

Forecast Discussion:

Today will be a nice day except for the cloud cover with highs in the lower to mid 60s.  Tonight chances of rain begin to creep in to the forecast with lows in the upper40s to lower 50s.  Friday we will see a good chance of rain and thunderstorms with highs in the lower 60s.  Some of the storms could be strong especially SW of most of East Tennessee toward Chattanooga.  Friday night rain showers continue with lows in the mid to upper 40s.

Extended Forecast Summary:

Good chances of rain continue into Saturday and colder air begins to move back into the area by Sunday and Monday.

Severe Weather Awareness Week:

Today's topic: Flooding

Flooding and Flash Flooding are the number one weather related killer!   
 
Most flood deaths occur at night and when people become trapped in automobiles that stall in areas that are flooded. 
 
Flash floods occur within a few minutes or up to 6 hours after excessive rainfall, a dam or levee 
failure, or a sudden release of water held by an ice jam or mud  slide. Flash floods can tear out trees and destroy buildings and bridges.  
 
Because flash floods happen in a short period of time, generally less than  six  hours, they  are
more life threatening than general floods or river flooding.  Areas most susceptible to flash  
flooding are mountainous  streams and rivers, urban areas, low-lying areas, storm drains, and culverts.  The  mountain regions of middle and east Tennessee have potentially more flash flood problems than west Tennessee but all parts of the state are susceptible. 
 
The National Weather Service issues a Flood Watch when conditions are detected that can
result in either flood or flash flooding within a designated area, but the occurrence is neither certain nor imminent.   
 
Persons in the watch area are advised to check flood action plans, keep informed, and be ready to take action if a warning is issued or flooding is observed. 

A Flash Flood Warning is issued when flash flooding has been reported or is imminent.  It
focuses on specific communities,  streams or areas where flooding is imminent or occurring. 

RIVER FLOODING: This type of flood is caused by an increased water level in an established watercourse, such as a river, creek, or drainage ditch.  River flooding is generally slower to  develop than flash flooding.  There can be exceptions to this, especially with some smaller rivers where the time lag between the runoff from heavy rain and the onset of flooding can be very short.  This can by the case with several east Tennessee rivers and streams.  On the other hand,  it may take several days for a flood crest to pass downstream points on major rivers.  
 
The  National Weather Service issues  River Flood Warnings when rivers are expected  to 
rise above flood stage in less than six hours.  Persons in the warned area are advised to take necessary precautions immediately. River stages and crest forecasts are given for selected forecast points along with known flood stages for each forecast point.   
 
While there is usually more advanced warning time with river floods than with flash floods,  
persons should be familiar with the flood prone areas they live and work in,  and must know what action to take and where to go if a flood occurs.  Advance planning and preparation is essential. 

FLOOD SAFETY RULES: 

Get out of areas subject to flooding. These include dips, low spots, 
stream beds, drainage ditches and culverts. If caught in low areas during 
flooding, go to high ground immediately. 
 
Avoid already flooded and high velocity flow areas. A rapidly flowing 
stream or ditch can sweep you off your feet or even sweep your car  
downstream. 
 
Be especially cautious at night when it is harder to recognize flood  
conditions. 
 
Do not drive through flooded areas. The road bed may be washed away.  
Play it safe. TURN AROUND, DON’T DROWN! 
 
If your vehicle stalls, abandon it immediately and seek higher ground.   
The rising water may engulf the vehicle and the occupants inside. 
 
Do not camp or park your vehicle along streams or washes during  
threatening conditions. 
 
When a Flash Flood WARNING is issued for your area act quickly to save  
yourself.  You may only have seconds. 



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