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Mesoscale Discussion 1072
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   Mesoscale Discussion 1072
   NWS Storm Prediction Center Norman OK
   0345 PM CDT Sat Jun 17 2017

   Areas affected...Portions of central/southern/eastern KS...western
   MO

   Concerning...Severe potential...Watch likely 

   Valid 172045Z - 172315Z

   Probability of Watch Issuance...80 percent

   SUMMARY...While not imminent, Weather Watch issuance will be likely
   at some point later this afternoon or early this evening -- for
   portions of the region. Significant severe hail and wind will be
   possible. The potential for a couple of tornadoes will also exist.

   DISCUSSION...Very strong to extreme instability has developed along
   and south of a surface boundary analyzed from south-central IA to
   near St. Joseph MO to just north of a line from Topeka to Salina.
   The boundary trails farther west into western KS. Near and south of
   the boundary, widespread strong insolation amid generally
   lower/middle 70s dewpoints and an EML characterized by 8-9-C/km
   midlevel lapse rates has resulted in MLCAPE of 4000-6500 J/kg.
   Deeper vertical mixing across western parts of southern KS is
   associated with a somewhat drier low-level profile and lower
   buoyancy.

   While these factors are yielding large conditional severe potential,
   there is substantial uncertainty regarding the timing of robust
   convective development. This is the result of strong capping 
   aloft -- perhaps related to compensating subsidence peripheral to a
   long-lived, decayed MCS presently crossing the Red River into far
   northeast TX. In fact, the 20Z Topeka KS special sounding indicates
   substantial capping, with MLCINH around 180 J/kg, associated with a
   shallow inversion around 850 mb beneath the base of the EML.

   Visible satellite trends suggest that the southern periphery of
   ACCAS fields are becoming slightly agitated across far northeast KS.
   This could be in response to a combination of slight midlevel
   cooling grazing the sloped frontal surface peripheral to a midlevel
   speed maximum, and/or diurnally enhanced boundary-layer 
   circulations -- augmented by frontal baroclinicity -- aided by
   diabatic surface-layer heating. Convection could develop in these
   areas of mesoscale ascent relatively soon despite the antecedent
   capping. Needless to say, observational data trends and CAM guidance
   are suggesting somewhat variable signals regarding timing/locations
   of convective initiation, and confidence in the timing and exact
   location of intense convective development are somewhat muted.

   Present indications are that supercell development could occur
   across parts of central and northeast KS and into northwest and
   west-central MO after 2130Z through around 0100Z -- but increasingly
   more likely after 2230-2330Z. This will be aided by continued
   surface heating and follow initial updraft pulsations along the zone
   of convergence attendant to the boundary -- and perhaps aided by the
   glancing influence of peripheral midlevel ascent. Additional
   development will be likely in the drier air westward along the front
   in KS.

   The presence of 40-50 kt of effective shear oriented obliquely to
   the initiating boundary will initially support discrete and
   semi-discrete supercell structures. Very large hail -- potentially
   baseball-size hail -- may accompany initial updrafts. Despite
   relatively weak low-level shear -- associated with slight diurnal
   veering of surface winds south of the boundary amid weak low-level
   flow -- intense stretching of pre-existing vertical vorticity will
   likely occur with maturing incipient updrafts interacting with the
   boundary. As such, some tornado risk could exist during early stages
   of convective development. The area of greatest potential for
   intense supercells capable of some tornado risk and significant
   severe hail will extend within a narrow corridor from around and
   south of the Salina and Fort Riley areas toward Topeka and Kansas
   City.

   However, there should be a tendency for convection to produce
   intense outflows -- given DCAPE of 1400-1800 J/kg amid the
   well-mixed boundary layer -- while increasing in coverage through
   the late afternoon and evening. This will likely curtail the
   spatiotemporal window of opportunity for tornado potential, while
   the risk for damaging straight-line winds increases. Amalgamating
   cold pools will have a tendency of supporting localized clusters of
   upscale convective growth as storms spread southeastward and
   east-southeastward into the evening hours. Severe winds --
   potentially destructive with gusts upwards of 80 mph -- will become
   increasingly likely as convection evolves into the evening hours.

   ..Cohen/Weiss.. 06/17/2017

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

   ATTN...WFO...SGF...EAX...TOP...ICT...DDC...

   LAT...LON   37109867 37279953 37659969 38009953 38429896 39199744
               39939509 40309396 40349325 39779312 38909344 38039459
               37409662 37109867 

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