Mesoscale Discussion 1686
   NWS Storm Prediction Center Norman OK
   1241 PM CDT Sat Aug 10 2019

   Areas affected...portions of eastern OR...far southeast
   WA...southwest and central ID and western MT

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

   Valid 101741Z - 101945Z

   Probability of Watch Issuance...80 percent

   SUMMARY...Thunderstorms will increase in coverage and intensity from
   far eastern OR into central ID and western MT over the next couple
   of hours. Large hail and damaging winds will be the main threats
   with these storms and a watch will likely be needed.

   DISCUSSION...Forcing for ascent is increasing across the northern
   Rockies late this morning, per increasing thunderstorm activity near
   the OR/ID border and more recently across central ID. Strong heating
   to the north and east of this activity is resulting in a quickly
   destabilizing airmass characterized by unusually high dewpoints,
   ranging from the low to mid 50s F mostly, but several areas are
   approaching 60F. As a result, MLCAPE increasing to around 1500 J/kg
   is expected in a swath from central ID into western MT by early
   afternoon. This should result in vigorous thunderstorm development
   over the next couple of hours over higher terrain. 

   Effective shear greater than 35 kt will allow cells to quickly
   become organized with rotating updrafts and possibly some supercell
   structures. Midlevel lapse rates are very steep, as evident in 12z
   regional RAOBs. Combined with favorable vertical shear profiles,
   large hail will be possible. Furthermore, storms will likely be
   high-based as boundary layer moisture mixes out with increased
   heating. Steepening low level lapse rates will result and fast storm
   motion will aid in strong wind gust potential as well. Where higher
   dewpoints are maintained, forecast guidance suggests there could be
   a brief, conditional tornado threat, mainly over parts of western MT
   where east/southeasterly low level flow will enhanced effective SRH.
   However, this threat is more uncertain than the expected large hail
   and strong, locally damaging gusts.

   The severe threat will continue to increase over the next couple of
   hours as additional heating reduces inhibition and forcing for
   ascent continues to increase. A severe thunderstorms watch will
   likely be needed by 19 or 20z.

   ..Leitman/Grams.. 08/10/2019

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

   ATTN...WFO...TFX...PIH...MSO...BOI...OTX...PDT...

   LAT...LON   45411096 44971189 44531336 44011425 43211496 42591549
               42261634 42171700 42421794 43091864 44141957 44701987
               45251985 45931919 46631814 47021743 47471571 47751386
               47711302 47411188 46831112 45861101 45411096