MESOSCALE DISCUSSION 1089
   NWS STORM PREDICTION CENTER NORMAN OK
   0350 PM CDT SAT JUN 20 2015

   AREAS AFFECTED...NORTHEASTERN WYOMING...FAR SOUTHEASTERN
   MONTANA...AND WESTERN SOUTH DAKOTA

   CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE 

   VALID 202050Z - 202245Z

   PROBABILITY OF WATCH ISSUANCE...40 PERCENT

   SUMMARY...ISOLATED THUNDERSTORMS HAVE DEVELOPED ACROSS WESTERN SOUTH
   DAKOTA...WITH A GRADUAL UPTICK IN THUNDERSTORM COVERAGE EXPECTED
   THROUGH THE EVENING.  TRENDS WILL BE MONITORED FOR A POSSIBLE WW
   ISSUANCE.

   DISCUSSION...A FEW THUNDERSTORMS HAVE DEVELOPED ACROSS NORTHWESTERN
   AND FAR WEST CENTRAL NORTH DAKOTA...AND A FEW TOWERING CU ARE NOTED
   VIA SATELLITE IMAGERY OVER ADJACENT AREAS OF NORTHEASTERN WYOMING.
   SURFACE TEMPERATURES RISING THROUGH THE 70S AND LOWER 80S HAVE
   ALLOWED FOR WEAK TO MODERATE INSTABILITY TO DEVELOP IN THE
   DISCUSSION AREA...WITH 500-1500 J/KG MLCAPE NOTED IN THE DISCUSSION
   AREA.  ALTHOUGH LOW-LEVEL WIND FIELDS ARE WEAK AND ONLY CONTAIN A
   VERY SLIGHT UPSLOPE COMPONENT...50-KNOT MID-LEVEL FLOW ALOFT OVER
   THE AREA IS CONTRIBUTING TO SUBSTANTIAL DEEP LAYER SHEAR FOR STORM
   ORGANIZATION.  OBSERVATIONS AND MODEL GUIDANCE SUGGEST A GRADUAL
   INCREASE IN CONVECTIVE DEVELOPMENT THROUGH THE EVENING...WITH ENOUGH
   SEVERE WIND/HAIL THREAT TO WARRANT CONSIDERATION OF A SEVERE
   THUNDERSTORM WATCH LATER THIS AFTERNOON/EARLY EVENING.  TRENDS WILL
   CONTINUE TO BE MONITORED.

   ..COOK/GUYER.. 06/20/2015


   ATTN...WFO...ABR...UNR...CYS...BYZ...RIW...

   LAT...LON   45850439 45620534 45260617 44790682 44370692 43930661
               43510585 43170436 43120339 43390224 43660170 43970135
               44420116 44780123 45530166 45860233 45890344 45850439