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Mesoscale Discussion 1003
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   Mesoscale Discussion 1003
   NWS Storm Prediction Center Norman OK
   0700 PM CDT Mon Jun 12 2017

   Areas affected...Portions of southern MT and northern/central WY

   Concerning...Severe Thunderstorm Watch 318...

   Valid 130000Z - 130130Z

   The severe weather threat for Severe Thunderstorm Watch 318
   continues.

   SUMMARY...An isolated threat for large hail and damaging winds
   continues across WW 318. A tornado or two also remains possible
   mainly across southern/eastern portions of the Watch.

   DISCUSSION...Convection has increased in coverage and intensity
   across northern/central WY over the past several hours as an upper
   low moves northeastward across the northern Great Basin. Strong mid
   to upper-level winds are contributing to generally 40-50 kt of
   effective bulk shear in/near the Severe Thunderstorm Watch. Although
   low-level moisture is more limited across this region (mid/upper 40s
   to mid 50s dewpoints) compared to southeastern WY, steep mid-level
   lapse rates overlying this sufficient moisture and diurnal heating
   have resulted in MLCAPE of 500-1500 J/kg. Multiple supercell
   structures have been observed per KRIW and KBLX radars, and isolated
   large hail and damaging winds will continue to be a threat through
   the evening hours as storms move northward into southern MT. A
   tornado or two will also remain possible, particularly across the
   Bighorn Basin and vicinity. Across this area, slightly greater
   low-level moisture (dewpoints in the low to mid 50s) is allowing for
   lower LCL heights, and a supercell over Johnson County WY has
   recently produced a tornado (as of 2342Z), along with 2+ inch hail.
   Diurnal cooling later this evening will act to reduce available
   instability to maintain storm intensity, and the overall severe
   threat should slowly lessen over the next few hours.

   ..Gleason.. 06/13/2017

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

   ATTN...WFO...BYZ...RIW...TFX...

   LAT...LON   44711100 46691065 46720783 45820637 44960607 43230617
               42810648 43010749 43390927 44041014 44711100 

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Page last modified: June 13, 2017
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