Mesoscale Discussion 1498
   NWS Storm Prediction Center Norman OK
   0242 PM CDT Sat Aug 15 2020

   Areas affected...Parts of northeastern Colorado and western Nebraska

   Concerning...Severe potential...Watch unlikely 

   Valid 151942Z - 152215Z

   Probability of Watch Issuance...20 percent

   SUMMARY...Isolated to widely scattered strong thunderstorms may
   continue to develop into the 4-6 PM MDT time frame.  It still seems
   unlikely that a severe weather watch will be needed, but trends will
   be monitored.

   DISCUSSION...Initiation of isolated strong storm development appears
   underway to the southeast of Chadron NE, near the dryline.  This
   might be aided by lift associated with weak mid-level warm
   advection, but forcing for large-scale ascent otherwise appears
   weak, to the south of a seasonably strong northwesterly mid/upper
   jet digging into the northern Great Plains.  Northwesterly mid-level
   flow is much more modest closer to the northern periphery of
   prominent mid-level subtropical ridging, across and to the lee of
   the Wyoming/Colorado Rockies, but veering of weak to modest wind
   fields with height does appear to be contributing sufficient shear
   for supercell structures along the dryline.  

   In the presence of steep/steepening lower through mid-tropospheric
   lapse rates, inhibition is becoming increasingly negligible along
   the dryline, where mixed-layer CAPE is becoming moderately large (on
   the order of 1500-2500+ J/kg) within a narrow corridor.  

   Further intensification of the ongoing storms seems probable, with
   isolated to widely scattered additional storm development possible
   through 22-00Z.  While the vertical shear is moderately strong,
   deep-layer mean ambient westerly/northwesterly flow is rather weak
   (around 15 kt or less).  As a result, any developing supercell
   structures likely will be slow moving, with a tendency to drift
   south-southwestward.  These probably will be accompanied by a risk
   for severe hail and locally strong surface gusts.  A short-lived,
   weak tornado/land spout or two may not be out of the question.

   ..Kerr/Grams.. 08/15/2020

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

   ATTN...WFO...LBF...GLD...BOU...CYS...

   LAT...LON   42660298 42640233 42220221 41080267 40170279 39750332
               40160363 42660298