Mesoscale Discussion 1511
   NWS Storm Prediction Center Norman OK
   0230 PM CDT Sun Aug 16 2020

   Areas affected...Much of interior Oregon and adjacent portions of
   the northern Intermountain Region

   Concerning...Severe potential...Watch unlikely 

   Valid 161930Z - 162200Z

   Probability of Watch Issuance...20 percent

   SUMMARY...Developing thunderstorm activity could be accompanied by
   increasing potential for strong to severe surface gusts through 3-5
   PM PDT.  While it currently seems unlikely that a severe weather
   watch will be needed, trends will continue to be monitored.

   DISCUSSION...Daytime heating is contributing to deep boundary-layer
   mixing across much of the region.  This will continue this
   afternoon, with moisture perhaps sufficient to contribute to CAPE up
   to 500 J/kg, particularly east of the Cascades.  While this is
   rather modest, it seems likely to become supportive of increasing
   thunderstorm development, aided by forcing for ascent associated
   with a short wave impulse migrating around the western periphery of
   prominent mid-level subtropical ridging.  While it appears that this
   will gradually turn northeastward across the Harney Basin through
   22-00Z, an associated convectively generated, mid-level cyclonic
   vorticity center is expected to migrate north of the
   California/Oregon state border, toward the Bend area.  

   Given the destabilization to the lee of the Cascades, the MCV may
   contribute to the most vigorous thunderstorm development.  However,
   even in convection developing to the east and southeast, sub-cloud
   thermodynamic profiles will be conducive to strong downbursts, aided
   by downward mixing of 30-50 kt flow in the cloud-bearing layer.

   Gradually, consolidating thunderstorm activity and convective
   outflow could yield increasingly widespread strong surface gusts
   while spreading northeastward through early evening.

   ..Kerr/Grams.. 08/16/2020

   ...Please see www.spc.noaa.gov for graphic product...

   ATTN...WFO...BOI...PDT...REV...MFR...PQR...

   LAT...LON   45551958 44641843 43031896 41771945 41182031 42032115
               42332175 42942260 44892216 45482159 45551958