SEVERE THUNDERSTORM WATCH FOR PORTIONS OF EXTREME SOUTHEAST MONTANA SOUTHWEST NORTH DAKOTA NORTHWEST SOUTH DAKOTA EFFECTIVE THIS MONDAY AFTERNOON AND EVENING FROM 255 PM UNTIL 1000 PM MDT.

 URGENT - IMMEDIATE BROADCAST REQUESTED
   SEVERE THUNDERSTORM WATCH NUMBER 487
   NWS STORM PREDICTION CENTER NORMAN OK
   255 PM MDT MON JUL 16 2012
   
   THE NWS STORM PREDICTION CENTER HAS ISSUED A
   SEVERE THUNDERSTORM WATCH FOR PORTIONS OF 
   
          EXTREME SOUTHEAST MONTANA
          SOUTHWEST NORTH DAKOTA
          NORTHWEST SOUTH DAKOTA
   
   EFFECTIVE THIS MONDAY AFTERNOON AND EVENING FROM 255 PM UNTIL
   1000 PM MDT.
   
   HAIL TO 2.5 INCHES IN DIAMETER...THUNDERSTORM WIND GUSTS TO 70
   MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE AREAS.
   
   THE SEVERE THUNDERSTORM WATCH AREA IS APPROXIMATELY ALONG AND 55
   STATUTE MILES NORTH AND SOUTH OF A LINE FROM 50 MILES SOUTH
   SOUTHWEST OF BAKER MONTANA TO 30 MILES EAST NORTHEAST OF MOBRIDGE
   SOUTH DAKOTA.  FOR A COMPLETE DEPICTION OF THE WATCH SEE THE
   ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU7).
   
   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.
   
   DISCUSSION...SEVERE STORMS ARE EXPECTED TO INCREASE AND DEVELOP EAST
   OFF THE HIGHER TERRAIN OF SERN MT AND WRN SD OVER THE NEXT COUPLE OF
   HOURS. DOWNSTREAM AIR MASS IS CHARACTERIZED BY STRONG INSTABILITY
   WHERE MOIST POST-FRONTAL LOW LEVEL ELY FLOW IS TOPPED BY 25-30KT
   SWLY FLOW ALOFT. RESULTING SHEAR AND THERMODYNAMIC REGIME SHOULD
   SUPPORT SUPERCELLS IF STORMS CAN PERSIST AND OVERCOME REMAINING
   INHIBITION EAST OF THE HIGHER TERRAIN. DESPITE WARM TEMPERATURES
   ALOFT...PERSISTENT LOW LEVEL CONVERGENCE ALONG THE FRONT AND
   THERMAL/TRIPLE-POINT LOW...AND MAGNITUDE OF HEATING ALONG AND SOUTH
   OF THE FRONTAL ZONE...SHOULD ACT TO OVERCOME REMAINING INHIBITION
   AND FAVOR AT LEAST A FEW SEVERE STORMS PRODUCING LARGE HAIL AND HIGH
   WINDS SPREADING EAST NEAR THE SD/ND BORDER AREA INTO THIS EVENING.
   
   AVIATION...A FEW SEVERE THUNDERSTORMS WITH HAIL SURFACE AND ALOFT
   TO 2.5 INCHES. EXTREME TURBULENCE AND SURFACE WIND GUSTS TO 60
   KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 500. MEAN STORM
   MOTION VECTOR 27025.
   
   
   ...CARBIN