Mesoscale Discussion 1705
   NWS Storm Prediction Center Norman OK
   0410 AM CDT Fri Sep 18 2020

   Areas affected...Northwest Oregon...Far Southwest Washington

   Concerning...Severe potential...Watch unlikely 

   Valid 180910Z - 181115Z

   Probability of Watch Issuance...5 percent

   SUMMARY...An isolated severe threat is expected to continue across
   parts of northwest Oregon and may affect far southwest Washington as
   well. Hail and strong wind gusts will be possible but the threat is
   expected to be too marginal for weather watch issuance.

   DISCUSSION...The latest surface analysis shows a narrow corridor of
   maximized low-level moisture from south-to-north in the Willamette
   Valley of northwestern Oregon. Surface dewpoints along this corridor
   are in the lower 60s F, which is contributing to MLCAPE estimated by
   the RAP in the 500 to 750 J/kg range. A small cluster of
   thunderstorms is ongoing along the instability axis. These storms
   have formed in response to a band of large-scale ascent that is
   spreading northward across western Oregon according to the
   water-vapor imagery and RAP 500 mb analysis. The storms are located
   in moderate deep-layer shear. The latest WSR-88D VWP at Portland has
   0-6 km shear near 35 kt with some speed shear in the mid-levels.
   This combined with the instability should be enough for an isolated
   severe threat over the next few hours. Hail and marginally severe
   wind gusts may occur with the stronger rotating storms.

   ..Broyles/Edwards.. 09/18/2020

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

   ATTN...WFO...SEW...PQR...

   LAT...LON   45182201 45772216 46252249 46372272 46392277 46422318
               46162360 45672375 45252368 44582342 44252300 44532227
               45182201