MESOSCALE DISCUSSION 0959
   NWS STORM PREDICTION CENTER NORMAN OK
   1044 AM CDT SAT JUN 06 2009
   
   AREAS AFFECTED...NE WY
   
   CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY 
   
   VALID 061544Z - 061715Z
   
   THE NEED FOR A WW IS NOT CURRENTLY ANTICIPATED...BUT TRENDS WILL BE
   MONITORED FOR THE POSSIBILITY OF AN INCREASING SEVERE THREAT.
   
   WATER VAPOR IMAGERY INDICATES A FAIRLY SIGNIFICANT MID-LEVEL
   CIRCULATION IS IN THE PROCESS OF LIFTING OUT OF THE NORTHERN GREAT
   BASIN.  THIS FEATURE IS EXPECTED TO WEAKEN WITHIN A CONFLUENT REGIME
   ACROSS THE NORTHERN ROCKIES INTO THE NORTHERN PLAINS...BUT FORCING
   IS EXPECTED TO BE SUFFICIENT TO SUPPORT THUNDERSTORM DEVELOPMENT
   ACROSS THE BIG HORNS VICINITY LATE THIS MORNING.  LIGHTNING DATA
   INDICATES THAT INITIATION IS ALREADY UNDERWAY...AS INHIBITION
   WEAKENS WITH HEATING ACROSS THE HIGHER TERRAIN.  
   
   STEEP MID-LEVEL LAPSE RATES APPEAR TO BE CONTRIBUTING TO MIXED LAYER
   CAPE ON THE ORDER OF 500 J/KG...BUT RUC GUIDANCE SUGGESTS THIS COULD
   INCREASE UP TO AROUND 1000 J/KG IN SOUTHEASTERLY UPSLOPE FLOW ACROSS
   NORTHEAST WYOMING BY THIS AFTERNOON.  GIVEN COOL THERMODYNAMIC
   PROFILES...POTENTIAL INSTABILITY...COUPLED WITH FAVORABLE DEEP LAYER
   SHEAR BENEATH 40-50+ KT 500 MB FLOW... PROBABLY WILL BE SUFFICIENT
   FOR A FEW STRONG/SEVERE STORMS CAPABLE OF PRODUCING AT LEAST
   MARGINALLY SEVERE HAIL.  THE TENDENCY SHOULD BE FOR ACTIVITY TO
   MOVE/PROPAGATE SOUTHEASTWARD ALONG A FRONTAL ZONE ACROSS NORTHEAST
   WYOMING...TO THE WEST OF THE BLACK HILLS... BETWEEN NOW AND 18-20Z.
   
   ..KERR.. 06/06/2009
   
   
   ATTN...WFO...UNR...CYS...RIW...
   
   LAT...LON   44260710 44580571 43380442 42610478 43060620 43380726
               44260710