Serious Severe WX Situation

June 18, 2009 — wxmanbill

A serious severe weather situation will unfold across eastern TN and southwest VA this afternoon as a derecho roars southeast into the region over the next couple of hours. Widespread damaging winds in excess of 70 MPH will be the primary threat as this mass of rain and leading edge of severe thunderstorm drops down into our region.  With temperatures in the lower 80s as of this post and dew points in the high 60s, our local air mass is plenty unstable to support severe.  Below is a graphic provided by the Storm Prediction Center.  Notice they label this is a PDS event, Particularly Dangerous Situation.

severe

SEL1
  
   URGENT – IMMEDIATE BROADCAST REQUESTED
   SEVERE THUNDERSTORM WATCH NUMBER 461
   NWS STORM PREDICTION CENTER NORMAN OK
   1040 AM EDT THU JUN 18 2009
  
   THE NWS STORM PREDICTION CENTER HAS ISSUED A
   SEVERE THUNDERSTORM WATCH FOR PORTIONS OF
  
          MUCH OF NORTHERN GEORGIA
          PARTS OF SOUTHERN KENTUCKY
          FAR WESTERN NORTH CAROLINA
          NORTHWESTERN SOUTH CAROLINA
          PARTS OF MIDDLE AND EASTERN TENNESSEE
  
   EFFECTIVE THIS THURSDAY MORNING AND EVENING FROM 1040 AM UNTIL
   600 PM EDT.
  
   …THIS IS A PARTICULARLY DANGEROUS SITUATION…
  
   EXTREMELY DAMAGING THUNDERSTORM WIND GUSTS TO 80 MPH…LARGE HAIL
   TO 2 INCHES IN DIAMETER…AND DANGEROUS LIGHTNING ARE POSSIBLE IN
   THESE AREAS.
  
   THE SEVERE THUNDERSTORM WATCH AREA IS APPROXIMATELY ALONG AND 85
   STATUTE MILES EAST AND WEST OF A LINE FROM 60 MILES NORTHEAST OF
   BOWLING GREEN KENTUCKY TO 35 MILES SOUTH SOUTHWEST OF ATHENS
   GEORGIA.  FOR A COMPLETE DEPICTION OF THE WATCH SEE THE
   ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU1).
  
   REMEMBER…A SEVERE THUNDERSTORM WATCH MEANS CONDITIONS ARE
   FAVORABLE FOR SEVERE THUNDERSTORMS IN AND CLOSE TO THE WATCH
   AREA. PERSONS IN THESE AREAS SHOULD BE ON THE LOOKOUT FOR
   THREATENING WEATHER CONDITIONS AND LISTEN FOR LATER STATEMENTS
   AND POSSIBLE WARNINGS. SEVERE THUNDERSTORMS CAN AND OCCASIONALLY
   DO PRODUCE TORNADOES.
  
   OTHER WATCH INFORMATION…CONTINUE…WW 459…WW 460…
  
   DISCUSSION…BOW ECHO/DERECHO IS MOVING RAPIDLY SEWD CENTRAL KY
   DRIVEN BY A 60-70 KT REAR INFLOW JET.  MORNING SOUNDINGS SWD INTO GA
   INDICATE THAT POTENTIALLY A VERY UNSTABLE AIR MASS IS IN PLACE IN
   ADVANCE OF THIS SYSTEM AND WITH DAYTIME HEATING…EXPECT THE CURRENT
   ASSOCIATED WIND DAMAGE TO BECOME MORE WIDESPREAD AND INTENSE.
  
   AVIATION…A FEW SEVERE THUNDERSTORMS WITH HAIL SURFACE AND ALOFT
   TO 2 INCHES. EXTREME TURBULENCE AND SURFACE WIND GUSTS TO 70
   KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 550. MEAN STORM
   MOTION VECTOR 33045.
  
  
   …HALES

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