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Mesoscale Discussion 1218
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   Mesoscale Discussion 1218
   NWS Storm Prediction Center Norman OK
   0804 PM CDT Sun Jul 02 2017

   Areas affected...southwest NE into northwestern KS

   Concerning...Severe Thunderstorm Watch 390...

   Valid 030104Z - 030200Z

   The severe weather threat for Severe Thunderstorm Watch 390

   SUMMARY...There appears to be an increasing risk (scattered
   coverage) for severe gusts (60-75 mph) as a squall line matures and
   intensifies as it moves south into southwestern NE and northwestern
   KS during the next several hours.

   DISCUSSION...Radar mosaic trends over the past 1-2 hours has shown
   cellular storms merging and upscale growth occurring near I-80 in
   west-central NE near North Platte.  The 00Z LBF raob exhibited steep
   lapse rates from the surface through the mid levels (8.3 degrees
   C/km in the 850-500 mb layer) with a well-mixed boundary layer
   beneath 700 mb.  Southeasterly low-level flow veering to westerly in
   the mid and high-levels is resulting in around 40-kt effective
   shear---supportive of storm organization.  A fairly sharp gradient
   in moisture is evident in 01Z surface observations with dewpoints in
   the mid 40s to mid 50s near the CO border to the lower-mid 60s near
   Hill City, KS.  A mesonet site at Kingsley Dam in Keith County, NE
   recorded a 77 mph gust at 0144Z.  

   Given the favorable low-level thermodynamic profile featuring a
   well-mixed/steep lapse rate profile and an organizing MCS, there is
   an expectation for severe gusts becoming spatially more expansive
   during the next several hours.  A recent model run of the HRRR takes
   this MCS south of the I-70 corridor around 05Z.  A spatial
   extension-in-area may need to be considered in the short term for
   Thomas, Sheridan, Graham, and Rooks counties in KS.

   ..Smith.. 07/03/2017

   ...Please see for graphic product...


   LAT...LON   39000153 40750269 41310124 41059937 39119903 39000153 

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