Mesoscale Discussion 0846
   NWS Storm Prediction Center Norman OK
   0750 PM CDT Sat Jun 23 2018

   Areas affected...Parts of western and central OK and extreme
   northwest TX

   Concerning...Severe Thunderstorm Watch 207...

   Valid 240050Z - 240145Z

   The severe weather threat for Severe Thunderstorm Watch 207
   continues.

   SUMMARY...Storm development remains possible yet this evening across
   western and central Oklahoma and adjacent extreme northwest Texas,
   though current thinking suggests severe potential may be isolated. 
   An additional severe-weather threat is being monitored for later
   tonight (after 2 AM CDT) for much of western, northern, and central
   Oklahoma, as the potential exists for a fast-moving line of storms
   (producing damaging winds) to track southeast from western Kansas.

   DISCUSSION...Trends in early evening local radar imagery and
   lightning data indicated a couple of storms forming across southwest
   OK (Greer and Jackson Counties) where the environment remained very
   unstable (MLCAPE exceeding 3000 J/kg) and effective bulk shear was
   increasing with time to at least 40 kt.  This CAPE/shear parameter
   space in addition to steep lapse rates and vertically veering winds
   per 00Z OUN sounding and an expected increase in southerly low-level
   winds across western OK suggest all severe hazards will be possible
   during the early evening.  A lack of discernible low-level
   convergence in the eastern part of WW 207 to focus storm development
   suggests this part of the watch could be canceled early.

   The latest runs of the operational HRRR indicated a
   forward-propagating MCS advancing to the southeast from eastern
   CO/western KS and reaching northwestern OK around 07Z (2 AM CDT),
   and into central OK by 10-11Z (5-6 AM CDT).  Given the reservoir of
   instability across the southern Plains and expected strengthening
   southerly low-level jet tonight, the short-term forecast confidence
   continues to increase with this scenario.

   ..Peters/Grams.. 06/24/2018

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

   ATTN...WFO...TSA...OUN...

   LAT...LON   33829894 33889946 34249999 35969995 35839873 36129849
               36089742 35859662 35119647 34619642 34189643 34019762
               33919796 34079834 34189899 33829894