MESOSCALE DISCUSSION 1598
   NWS STORM PREDICTION CENTER NORMAN OK
   0630 PM CDT TUE JUL 12 2011
   
   AREAS AFFECTED...PARTS OF ERN ID AND WRN/CENTRAL MT
   
   CONCERNING...SEVERE THUNDERSTORM WATCH 637...
   
   VALID 122330Z - 130030Z
   
   THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH 637
   CONTINUES.
   
   A SLOW ESEWD MOVING CLOSED UPPER LOW LOCATED ALONG THE WA/ORE COAST
   IS MAINTAINING A BAND OF 35-40 KT SSWLY MIDLEVEL WINDS EXTENDING
   FROM ERN ORE TO WRN-NORTH CENTRAL MT.  THIS FLOW COUPLED WITH ELY
   LOW LEVEL WINDS OVER MT IS CONTINUING TO RESULT IN EFFECTIVE BULK
   SHEAR OF 30-40 KT ACROSS MUCH OF WW 637...WITH THE STRONGEST SHEAR
   LOCATED OVER WRN/NRN PARTS OF THIS WATCH.  OBJECTIVE ANALYSES SHOWED
   A GENERALLY N-S CORRIDOR OF MODERATE INSTABILITY IN CENTRAL MT /ERN
   EXTENT OF WW 637/...WITH MODERATE INSTABILITY ALSO EXTENDING SWWD
   FROM NRN MT INTO SRN EXTENT OF THE ID PANHANDLE.  THIS LATTER
   INSTABILITY CORRIDOR SHOULD REMAIN THE PRIMARY ZONE OF TSTM
   DEVELOPMENT/SEVERE WEATHER THREAT.  THIS AREA COINCIDES WITH
   STRONGER FLOW ALOFT AND ATTENDANT TO ONE OR TWO MIDLEVEL IMPULSES
   TRACKING NNEWD INTO AND ACROSS WRN MT THIS EVENING.
   
   DEEP LAYER SHEAR IS WEAKER WITH SSEWD EXTENT ACROSS SOUTH CENTRAL MT
   INTO NRN WY WITH THESE STORMS HAVING BEEN PRIMARILY OUTFLOW
   DOMINATED.  GIVEN THIS TREND AND LIMITED POTENTIAL FOR ADDITIONAL
   ACTIVITY...A FEW COUNTIES WILL BE REMOVED FROM THIS WATCH BY WFO
   BILLINGS.
   
   ..PETERS.. 07/12/2011
   
   
   ATTN...WFO...BYZ...GGW...RIW...TFX...PIH...MSO...BOI...
   
   LAT...LON   44851480 47191427 49061194 49020813 47680874 47340846
               46230893 45130973 44581105 44461138 44181243 44101312
               44851480