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Mesoscale Discussion 1001
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   Mesoscale Discussion 1001
   NWS Storm Prediction Center Norman OK
   0605 PM CDT Mon Jun 12 2017

   Areas affected...Portions of eastern WY...southwestern SD...western
   NE...and northeastern CO

   Concerning...Tornado Watch 317...

   Valid 122305Z - 130030Z

   The severe weather threat for Tornado Watch 317 continues.

   SUMMARY...All severe hazards, including strong tornadoes, large to
   giant hail, and damaging winds will continue with multiple
   supercells across Particularly Dangerous Situation Tornado Watch
   317. A downstream watch into western/central NE and southern SD will
   be needed within the next several hours.

   DISCUSSION...At least 3 supercells are ongoing as of 23Z across far
   southeastern WY/northeastern CO into far western NE. With a very
   favorable thermodynamic and kinematic environment characterized by
   MLCAPE of 2000-3500 J/kg and effective bulk shear of 50-60 kt, these
   supercells have produced over a dozen reports of significant hail (2
   inch in diameter or greater) over the past few hours, with several
   reports of hail greater than 4 inches. At least 2 tornadoes have
   also occurred. The airmass downstream of ongoing convection will
   easily support continued significant severe hail, along with a risk
   for tornadoes and damaging winds through this evening. Strong
   tornadoes will continue to be a possibility with any discrete
   supercell across far southeastern WY, northeastern CO, and western
   NE for the next few hours given a strongly veering and strengthening
   wind profile with height. Of note, 0-1 km SRH is around 300 m2/s2
   per recent VWP from KCYS, and 0-3 SRH is around 500 m2/s2.

   A southerly low-level jet will strengthen to around 40-50 kt across
   western/central NE into southern SD this evening/tonight, and all
   severe hazards will remain possible into this evening across these
   areas. Evolution from discrete supercells into one or more bowing
   line segments appears likely to occur at some point later this
   evening in tandem with the increasing low-level jet, which would
   likely increase the threat for damaging winds with eastward extent.
   In addition, large hail and a few tornadoes should continue to be a
   threat with any supercell embedded within the line(s). A downstream
   watch in western/central NE and southern SD will be needed within
   the next several hours.

   ..Gleason.. 06/12/2017

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

   ATTN...WFO...LBF...UNR...BOU...CYS...

   LAT...LON   40710518 42620583 43380588 43930587 44120395 44060122
               43690104 40550104 40500363 40610455 40710518 

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Page last modified: June 13, 2017
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