Mesoscale Discussion 1655
   NWS Storm Prediction Center Norman OK
   0725 PM CDT Mon Aug 30 2021

   Areas affected...portions of southern South Dakota and northern
   Nebraska

   Concerning...Severe Thunderstorm Watch 477...

   Valid 310025Z - 310300Z

   The severe weather threat for Severe Thunderstorm Watch 477
   continues.

   SUMMARY...Large hail and strong wind gusts will remain possible
   across WW 477 the next few hours. A hail and damaging-wind threat
   may develop downstream across parts of southern South Dakota and
   northern Nebraska this evening and this area is being monitored for
   possible watch issuance.

   DISCUSSION...Isolated severe thunderstorms continue this evening
   across western South Dakota within Severe Thunderstorm Watch 477.
   Very large hail continues to be the main hazard with this activity
   and should persist for another couple of hours. 

   Downstream evolution of the severe threat continues to be somewhat
   uncertain across parts of south-central/southeast SD and
   north-central/northeast NE. An agitated CU field over Cherry County
   NE has shown increasing vertical development over the past hour or
   so, with several TCU noted in visible satellite imagery. HRRR
   guidance has struggled to accurately depict ongoing convection
   across the region in a weak forcing regime. But most guidance has
   been consistent in developing east/southeastward-advancing
   thunderstorm clusters across southern SD into northern NE this
   evening. The 00z RAOB from LBF indicates inhibition has weakened
   considerably since the 18z LBF RAOB. The overall environment
   downstream from WW 477 remains favorable for severe storms given
   strong vertical shear and moderate instability. A subtle shortwave
   impulse shifting eastward from WY may be sufficient amid a
   developing southerly low level jet across the region to support
   additional thunderstorm development this evening. Coverage and
   timing remains uncertain, but a downstream watch may be needed in
   the next few hours downstream from WW 477.

   ..Leitman/Edwards.. 08/31/2021

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

   ATTN...WFO...FSD...OAX...ABR...LBF...UNR...

   LAT...LON   43580261 44210262 44750226 44980173 44840051 44529929
               43999833 43659782 43259725 42919697 42439694 42169716
               42019774 41979810 41979880 42020011 42190086 42630164
               43210232 43580261