Mesoscale Discussion 1483
   NWS Storm Prediction Center Norman OK
   0642 PM CDT Mon Jul 15 2019

   Areas affected...Eastern Wyoming into southwestern South Dakota and
   western into central Nebraska

   Concerning...Severe Thunderstorm Watch 510...

   Valid 152342Z - 160115Z

   The severe weather threat for Severe Thunderstorm Watch 510
   continues.

   SUMMARY...The severe threat continues across Severe Thunderstorm
   Watch 0510. Large hail and severe wind gusts remain the primary
   threat. Upscale growth of convection remains possible across
   northwestern portions of the watch, where severe winds may become
   the predominant threat. Outflow from earlier storms have stabilized
   the airmass across southeast parts of the watch, where the short
   term severe threat has been tempered.

   DISCUSSION...Semi-discrete to discrete storms, including transient
   supercell structures, have developed and matured across the
   lower-terrain areas in eastern Wyoming over the past few hours.
   Ample buoyancy (1500-2500 J/kg MLCAPE) and adequate deep-layer shear
   (35-45 knots of bulk effective shear) are in place to foster the
   maintenance of this convection. Poor speed and directional shear in
   the lowest 3 km, however, suggests that some outflow dominant
   tendencies should exist with some of the more intense cells with
   more robust, water/hail loaded downdrafts. As such, cold-pool
   merging is expected to commence over the next few hours, promoting
   upscale growth for potential MCS development, as suggested by both
   the 12Z HREF and the last few runs of the HRRR. Should this occur,
   severe wind gusts should become the main threat, particularly in far
   east WY into southwest SD. The intensity of the potential MCS is
   somewhat uncertain, as a meager to negligible low-level jet is
   expected to develop during the evening. As such, robustness of the
   MCS will depend entirely on cold pool propagation processes, and the
   amount of buoyancy available ahead of the convective leading line.

   Meanwhile, multicellular convection in northern Nebraska, supported
   by 3000+ J/kg MLCAPE, have exhibited copious outflow given the very
   weak low-level and deep-layer shear environment in place. A
   substantial cold pool has been left behind across southeast parts of
   Severe Thunderstorm Watch 0510, suggesting that the severe threat
   has been dampened to a degree via boundary layer stratification and
   mid-level convective overturning/diminishing of lapse rates. Still,
   at least a few hours of diurnal heating remain, and the chances for
   additional severe weather will hinge on the trajectory and intensity
   of the potential aforementioned MCS.

   ..Squitieri/Grams.. 07/15/2019

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

   ATTN...WFO...ABR...LBF...UNR...CYS...BYZ...RIW...

   LAT...LON   41280519 44830716 44820124 41289960 41280519