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Mesoscale Discussion 730
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   Mesoscale Discussion 0730
   NWS Storm Prediction Center Norman OK
   1156 PM CDT Wed Jun 13 2018

   Areas affected...Parts of the mid Missouri Valley

   Concerning...Severe potential...Watch unlikely 

   Valid 140456Z - 140730Z

   Probability of Watch Issuance...20 percent

   SUMMARY...Increasing thunderstorm development, which could be
   accompanied by a risk for severe hail, appears possible by 3-4 AM
   CDT.  It is not anticipated that this will require a severe weather
   watch, but trends will be monitored.

   DISCUSSION...A fairly broad area of lower/mid tropospheric warm
   advection has evolved across much of the north central Plains/mid
   Missouri Valley region.  This is generally focused beneath and on
   the northeastern periphery of a broad plume of warm elevated mixed
   layer air emanating from the Great Basin.  Associated forcing for
   ascent near the edge of the stronger capping appears to be
   contributing to ongoing convective development near Sioux City IA. 
   This is likely being supported by weak CAPE associated with elevated
   moisture return (perhaps near/above 700 mb), emanating from richer
   low-level moisture beneath the cap, generally across the higher
   plains to the west of the Missouri river.  

   However, latest VWP data from Hastings and North Platte indicate
   that southerly low-level jet strengthening to 40-50 kt centered
   around 1 km AGL has taken place during the past few hours.  Peak
   speeds will likely be reached within the next hour or two, with a
   subsequent weakening, but gradually veering of the jet to a
   southwesterly component through 07-09Z.  As this takes place,
   advection of low-level moisture into the vicinity of the mid-level
   moisture gradient is expected to contribute to considerable
   destabilization near/northeast of the Missouri River.  Most
   convection allowing guidance, including the NCEP HRRR indicate that
   this will coincide with increasing/intensifying thunderstorm
   development.   In the presence of at least modest vertical shear,
   supported by considerable veering of winds with height, the
   development of moderately large CAPE may support a severe hail
   threat in stronger storm development.

   ..Kerr/Weiss.. 06/14/2018

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

   ATTN...WFO...DMX...FSD...OAX...

   LAT...LON   44059777 44059597 42219416 41549473 41759584 42709670
               43509781 44059777 

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Page last modified: June 14, 2018
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