Mesoscale Discussion 1861
   NWS Storm Prediction Center Norman OK
   0105 AM CDT Mon Aug 26 2019

   Areas affected...Portions of central/southern SD and
   northern/central NE

   Concerning...Severe Thunderstorm Watch 620...621...

   Valid 260605Z - 260700Z

   The severe weather threat for Severe Thunderstorm Watch 620, 621
   continues.

   SUMMARY...Severe, damaging wind gusts will likely remain the primary
   threat across Severe Thunderstorm Watches 620 and 621 in the short
   term. The greatest severe risk will be with a small bowing cluster
   in northern/central Nebraska.

   DISCUSSION...Storms have congealed into a broken line along/ahead of
   a surface front from central SD southward into parts of northern NE.
   These storms are being supported by a convectively augmented
   shortwave trough moving eastward across the northern Plains. A
   veering wind profile with height through low/mid levels and the
   presence of a 55-60 kt mid-level jet is providing ample shear to
   support storm organization. Latest objective analysis suggests this
   ongoing activity is moving across a relative maximum in instability,
   which is located in a narrow north-south corridor from south-central
   SD into parts of northern/central NE. Mid-level lapse rates quickly
   weaken with eastward extent in SD/NE, as shown by the 00Z sounding
   from OAX. Low-level moisture also gradually decreases from central
   into eastern NE per recent surface observations. Strong to severe
   winds will likely remain the primary threat in the short term given
   a linear storm mode dominating. The small cluster moving quickly
   southeastward around 40 kt across northern/central NE should have
   the greatest potential to produce severe winds. Current expectations
   are for these storms to slowly weaken as they move eastward into a
   progressively less unstable airmass. Downstream watch issuance may
   not be needed if this weakening trend occurs as expected.

   ..Gleason.. 08/26/2019

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

   ATTN...WFO...FSD...ABR...GID...LBF...UNR...

   LAT...LON   41660150 42090160 43180129 43560107 43920098 44320079
               44360039 44019972 42839843 41999860 41259924 41200025
               41660150