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Storm Prediction Center Mesoscale Discussion 1903

   Mesoscale Discussion 1903
   NWS Storm Prediction Center Norman OK
   0451 PM CDT Tue Oct 26 2021

   Areas affected...portions of southwest Nebraska into central Kansas
   and northwest Oklahoma

   Concerning...Severe potential...Watch likely 

   Valid 262151Z - 262315Z

   Probability of Watch Issuance...95 percent

   SUMMARY...The potential for severe thunderstorms is increasing
   within the warm sector, ahead of the cold front/dryline. Damaging
   gusts appear to be the main threats though a couple tornadoes and
   instances of large hail are also possible. A WW issuance is expected
   by 23Z.

   DISCUSSION...Latest METAR observations depict the gradual eastward
   movement of the dryline and cold front across the central Plains
   given the approach of a deepening surface low and couple mid-level
   trough. Convective inhibition continues to erode as the boundary
   layer mixes and surface temperatures exceed 80F and dewpoints
   approach the mid 60s F. 8-8.5 C/km mid-level lapse rates are
   overspreading the warm/moist low level airmass, contributing to
   1500-2000 J/kg MLCAPE. Simultaneously, intensifying southerly
   low-level flow with the approaching upper trough will contribute to
   intensifying deep-layer and low-level shear, with up to 50 kts of
   effective bulk shear and 400 m2/s2 effective SRH expected to develop
   ahead of the dryline in the next few hours, when convective
   initiation will occur. 

   Meridional/unidirectional tropospheric wind profiles and strong
   forcing for ascent ahead of a merging dryline/cold front suggests
   that transient supercell structures will develop and rapidly merge
   into line segments/squalls. The well-mixed boundary layer and up to
   50 kt 850 mb flow suggests that strong to severe gusts should easily
   reach the surface within and in advance of any well-developed storm
   cores/line segments. Occasional bouts of large hail are also
   expected given the 8+ C/km mid-level lapse rates. Though modest,
   some low-level directional shear is evident in RAP forecast
   soundings, suggesting that the more persistent supercells or
   dominant storms embedded within the squall may acquire occasional,
   strong low-level rotation, with at least a couple tornadoes
   possible. However, the degree of tornado potential will be largely
   dependent on the number of discrete/dominant storms that can form
   and how long they persist, which remains uncertain. Nonetheless,
   organized severe storms are expected in the next few hours, and a WW
   will be issued to address this threat.

   ..Squitieri/Hart.. 10/26/2021

   ...Please see for graphic product...


   LAT...LON   35769974 36430009 37160018 38090035 39100060 40290093
               40840079 41110059 41200025 40849966 40159898 39439854
               38429798 37499781 36879785 36309814 35839841 35559897
               35589944 35769974