MESOSCALE DISCUSSION 0938
   NWS STORM PREDICTION CENTER NORMAN OK
   0235 PM CDT WED JUN 03 2009
   
   AREAS AFFECTED...PARTS OF NE CA...NW NV...INTO S CNTRL/SE OREGON
   
   CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE 
   
   VALID 031935Z - 032100Z
   
   TRENDS ARE BEING MONITORED FOR AN INCREASING SEVERE THREAT AND THE
   POSSIBILITY OF A WW LATER THIS AFTERNOON.
   
   VIGOROUS CONVECTIVE DEVELOPMENT IS ALREADY WELL UNDERWAY ACROSS THE
   NORTHERN SIERRA NEVADA INTO THE SHASTA/SISKYOU REGION.  FAVORABLE
   LARGE-SCALE FORCING...ASSOCIATED WITH A SHORT PIVOTING THROUGH THE
   EASTERN PERIPHERY OF THE CLOSED LOW CENTERED OFF THE CALIFORNIA
   COAST...HAS AUGMENTED OROGRAPHIC LIFT/DESTABILIZATION ...AND THIS
   LIKELY WILL PERSIST THROUGH MUCH OF THE AFTERNOON.  WEAK TO MODERATE
   POTENTIAL INSTABILITY COUPLED WITH MODERATELY STRONG DEEP LAYER
   SHEAR BENEATH A 50-70+ KT SOUTHERLY 300 MB JET MAY SUPPORT SUPERCELL
   STRUCTURES CAPABLE OF PRODUCING LARGE HAIL AND DAMAGING WIND GUSTS.
   
   SOUTHERLY STEERING FLOW IS EXPECTED TO CONTRIBUTE TO THE GRADUAL
   DEVELOPMENT OF ACTIVITY TO THE NORTHEAST OF THE MOUNTAINS...WHERE
   DAYTIME HEATING OF A RELATIVELY MOIST AIR MASS WILL CONTRIBUTE TO 
   DESTABILIZATION MORE SUPPORTIVE OF BOUNDARY LAYER BASED STORM
   DEVELOPMENT BY 22-00Z.  THOUGH LOW-LEVEL HODOGRAPHS ARE NOT
   PARTICULARLY LARGE...THEY ARE CLOCKWISE CURVED DUE TO THE EASTERLY
   COMPONENT OF THE NEAR SURFACE WINDS.  THIS COULD CONTRIBUTE TO 
   POTENTIAL FOR AN ISOLATED BRIEF TORNADO...BUT THE RISK FOR LARGE
   HAIL AND LOCALIZED DAMAGING WIND GUSTS SHOULD PREDOMINATE.
   
   ..KERR.. 06/03/2009
   
   
   ATTN...WFO...BOI...LKN...REV...HNX...MFR...STO...
   
   LAT...LON   38842044 39682081 40482167 41262196 42382190 43012109
               42591915 40731803 39291823 38261869 37241917 38842044