Mesoscale Discussion 0765
   NWS Storm Prediction Center Norman OK
   0120 PM CDT Sat May 30 2020

   Areas affected...central Oregon into south-central Washington

   Concerning...Severe potential...Severe Thunderstorm Watch likely 

   Valid 301820Z - 302015Z

   Probability of Watch Issuance...95 percent

   SUMMARY...Thunderstorms are expected to develop by 20z. A watch will
   likely be issued in the next 1-2 hours.

   DISCUSSION...Strong heating is occurring across much of central OR
   where cloud cover has been limited compared to areas to the west and
   south. Vertical development to cumulus over the higher terrain from
   Klamath into Lake Counties has been noted in recent visible
   satellite loops. Additionally, higher-based ACCAS has also increased
   across south-central OR. With additional increases in CU development
   over northern NV and northern CA, it appears increasing ascent is
   spreading into the region as the shortwave trough/upper low pivots
   northeast. 

   Temperatures have already warmed into the mid 70s to low 80s across
   the region, with dewpoints generally in the 50s F, through some low
   60s dewpoints are noted closer to the Pendleton vicinity. As a
   result, MUCAPE values are already increasing 500-1500 J/kg over
   portions of the MCD area. Destabilization is expected to continue
   spreading north/northwest into north-central OR/south-central WA
   vicinity through the afternoon. Effective shear greater than 45 kt
   is already in place across the region in conjunction with midlevel
   lapse rates from 7-8 C/km. This will support initial high-based
   supercell development by 20z. Steep low level lapse rates will
   support strong downdrafts and some upscale development of storms
   could occur via outflow interactions/cold pool development as
   convection tracks generally northward toward north-central OR.
   Forecast guidance continues to indicate a swath of damaging winds,
   some greater than 65 kt, is possible from central into north-central
   OR and south-central WA through 00z. Large hail also is possible,
   especially with any more discrete cells prior to upscale development
   given strong shear and steep midlevel lapse rates. Finally, recent
   VWP data from PDT shows favorable low level shear, with 0-3km SRH
   greater than 250 m2/s2. While the tornado threat will likely be
   limited by the higher-based nature of convection, a tornado or two
   can not be entirely ruled out, though intense, damaging winds will
   be the main concern through this evening.

   ..Leitman/Grams.. 05/30/2020

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

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

   LAT...LON   42312099 42202159 42312206 42602235 44892203 45642179
               45772163 45902153 46232072 46341994 46381936 46301885
               46081847 45901823 45591813 44911828 43421969 42482053
               42312099