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Mesoscale Discussion 1646
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   Mesoscale Discussion 1646
   NWS Storm Prediction Center Norman OK
   0322 PM CDT Sun Aug 30 2020

   Areas affected...far southern North Dakota...most of central and
   east central South Dakota...northern Nebraska

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

   Valid 302022Z - 302215Z

   Probability of Watch Issuance...80 percent

   SUMMARY...Severe thunderstorms are expected to develop along a cold
   front/dryline in the next few hours. These storms will likely be
   severe and one or more severe thunderstorm watches will likely be
   needed later this afternoon.

   DISCUSSION...Elevated convection has been ongoing for most of the
   day across North Dakota along and behind a cold front. Limited
   moisture and extensive cloud cover in this area has limited
   instability and thus precluded any severe weather concerns up to
   this point. Farther south, temperatures are heating up ahead of the
   cold front across South Dakota. This region has been capped for most
   of the day, but an expanding cumulus field on visible satellite
   across northern South Dakota, and SPC mesoanalysis now suggesting
   less than 50 J/kg MLCIN shows the inhibition has weakened. Another
   hour or two of heating should sufficiently destabilize the airmass
   along the front and allow for rapid thunderstorm development along
   the front. Additional development is possible along a dryline which
   currently extends from near KPIR to west of KTIF as of 20Z. MLCAPE
   has increased to ~2500 J/kg and mid-level lapse rates are around 8.5
   C/km per SPC mesoanalysis. This favorable thermodynamic environment
   will support robust updraft growth once the cap breaks. Currently,
   mid-level flow is quite weak across the warm sector, but at least
   some stronger mid-level flow is expected to overspread the warm
   sector late this afternoon/this evening which should aid in storm
   organization. The moderate to strong instability and very steep
   mid-level lapse rates will be supportive of very large hail,
   primarily in this initial stages of storm development before storms
   grow upscale along the front.

   The severe weather threat should not last that long, as storms will
   quickly move through the narrow moisture axis and start to encounter
   a more stable airmass with eastward extent after only a few hours.
   Nonetheless, several severe storms (including some capable of very
   large hail) are anticipated along the cold front this evening for a
   few hours. One or more severe thunderstorm watches will likely be
   needed once storm initiation appears imminent.

   ..Bentley/Grams.. 08/30/2020

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

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

   LAT...LON   41230141 42220117 43170087 43980074 44880086 45550075
               46230014 46739933 46919874 46499775 44319796 42169852
               41059970 40800080 41230141 

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Page last modified: August 30, 2020
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