SEL8
   
   URGENT - IMMEDIATE BROADCAST REQUESTED
   TORNADO WATCH NUMBER 178
   NWS STORM PREDICTION CENTER NORMAN OK
   335 PM CDT THU APR 21 2005
   
   THE NWS STORM PREDICTION CENTER HAS ISSUED A
   TORNADO WATCH FOR PORTIONS OF 
   
          SOUTHWESTERN IOWA
          EASTERN KANSAS
          NORTHWEST MISSOURI
          SOUTHEAST NEBRASKA
   
   EFFECTIVE THIS THURSDAY AFTERNOON AND EVENING FROM 335 PM UNTIL
   1100 PM CDT.
   
   TORNADOES...HAIL TO 3 INCHES IN DIAMETER...THUNDERSTORM WIND GUSTS
   TO 80 MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE AREAS.
   
   THE TORNADO WATCH AREA IS APPROXIMATELY ALONG AND 75 STATUTE MILES
   EAST AND WEST OF A LINE FROM 25 MILES WEST NORTHWEST OF OMAHA
   NEBRASKA TO 55 MILES SOUTH SOUTHWEST OF KNOB NOSTER MISSOURI.  FOR
   A COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH OUTLINE
   UPDATE (WOUS64 KWNS WOU8).
   
   REMEMBER...A TORNADO WATCH MEANS CONDITIONS ARE FAVORABLE FOR
   TORNADOES AND 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.
   
   OTHER WATCH INFORMATION...THIS TORNADO WATCH REPLACES TORNADO
   WATCH NUMBER 175. WATCH NUMBER 175 WILL NOT BE IN EFFECT AFTER 335
   PM CDT. CONTINUE...WW 176...WW 177...
   
   DISCUSSION...AS VIGOROUS TROUGH CENTRAL KS/NE MOVES EWD SEVERE
   THUNDERSTORMS WILL BECOME MORE WIDESPREAD ACROSS WATCH AREA.  WITH
   ENHANCED SHEAR VICINITY WARM FRONT...ALONG WITH STRONG
   INSTABILITY...SUPERCELLS ASSOCIATED TORNADO THREAT WILL INCREASE
   INTO EVENING HOURS AS DEVELOPMENT CONTINUES TO SPREAD EWD ACROSS
   WATCH AREA.
   
   AVIATION...TORNADOES AND A FEW SEVERE THUNDERSTORMS WITH HAIL
   SURFACE AND ALOFT TO 3 INCHES. EXTREME TURBULENCE AND SURFACE WIND
   GUSTS TO 70 KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 550.
   MEAN STORM MOTION VECTOR 26030.
   
   
   ...HALES