Mesoscale Discussion 0598
   NWS Storm Prediction Center Norman OK
   0108 PM CDT Fri May 15 2020

   Areas affected...Portions of central/southern OK into western north
   TX and north TX

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

   Valid 151808Z - 152015Z

   Probability of Watch Issuance...95 percent

   SUMMARY...The threat for scattered large hail and damaging winds
   will rapidly increase this afternoon. Severe thunderstorm watch
   issuance will be needed soon.

   DISCUSSION...Storms persist this afternoon across parts of central
   into eastern OK along a composite outflow boundary/front. This front
   is expected to continue sagging southward across central/southern OK
   this afternoon, and it will likely provide a focus for severe storm
   development. A 17Z special sounding from OUN shows minimal
   convective inhibition remaining, with steep 700-500 mb layer lapse
   rates around 7-7.5 C/km. A very moist low-level airmass and diurnal
   heating to the south of the front are also contributing to MLCAPE of
   2000-4000+ J/kg.

   Even with this strong to locally extreme instability, mid-level flow
   and related effective bulk shear is not expected to be overly
   strong, only around 25-35 kt. This should still be sufficient for
   storm organization, with any initially discrete development capable
   of producing very large hail (2+ inches in diameter). With marginal
   shear and the linear low-level forcing of the front, tendency should
   be for storms to quickly congeal into multiple clusters/bows.
   Scattered to numerous severe, damaging winds gusts will likely
   become an increasing concern later this afternoon into the early
   evening as storms propogate generally southward into greater
   instability. The tornado threat appears to be relatively limited
   given the weak low-level flow. But, a tornado cannot be entirely
   ruled out, mainly along the front early in the convective life cycle
   while storms remain semi-discrete.

   Across southwest OK into western north TX, additional storms may
   form the east of a weak surface low and related dryline currently
   located near CDS. This convection would likely have a more eastward
   component of motion, and may merge with any storms that form across
   western OK along/ahead of the front. Regardless, scattered large
   hail and severe winds gusts may occur south of the front and east of
   the dryline, and a Severe Thunderstorm Watch will be needed across
   much of central/southern OK and western north TX soon. Somewhat more
   uncertainty exists regarding the southward extent of the severe
   threat into parts of north TX through the early evening.

   ..Gleason/Dial.. 05/15/2020

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

   ATTN...WFO...SHV...TSA...FWD...OUN...

   LAT...LON   35149733 35079644 34989550 35039481 34419450 33559486
               33499624 33519807 33519960 33869995 34819993 35249972
               35539897 35529801 35149733