SPC AC 091956

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0256 PM CDT Tue Jun 09 2020

   Valid 092000Z - 101200Z

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS
   OF SOUTHEASTERN NEBRASKA AND NORTHEASTERN KANSAS...

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PORTIONS OF
   THE MIDWEST...

   ...SUMMARY...
   Scattered severe thunderstorms capable of large hail, damaging
   winds, and a few tornadoes are expected this afternoon and evening
   across parts of the central Plains and Missouri Valley. Other
   isolated severe storms including the possibility of a few tornadoes
   are expected across the Midwest and Ohio Valley.

   ...Discussion...
   No appreciable changes are being made to the outlook at this time,
   as both areas and meteorological reasoning as laid out in prior
   forecasts appears to remain representative of current expectations. 


   Storms are forecast to continue to increase in coverage/intensity
   over the southeast Nebraska/northeast Kansas vicinity over the next
   few hours, hence the recent issuance of Tornado Watch 273 in this
   area.  For additional short-term information, please refer to SWOMCD
   #889.

   Elsewhere, convection -- along with local tornado/wind potential --
   remains evident over portions of the Midwest vicinity in proximity
   to the remnants of Cristobal this afternoon and into this evening.

   ..Goss.. 06/09/2020

   .PREV DISCUSSION... /ISSUED 1125 AM CDT Tue Jun 09 2020/

   ...Northeast KS/southeast NE this afternoon/evening...
   An unusually amplified pattern persists for early June, with a deep
   midlevel trough moving eastward from CO/NM toward KS/OK, and the
   remnants of tropical cyclone Cristobal (now west of Saint Louis)
   moving north-northeastward toward WI/Upper MI by tonight.  In
   advance of the deep midlevel trough now approaching western KS and
   the TX Panhandle, a 995 mb surface cyclone is expected to move
   eastward from north central KS this morning to northeast KS by this
   evening, as a trailing cold front surges eastward across OK/TX.  A
   corridor of 68-70 F boundary-layer dewpoints will arc back
   northwestward to the surface cyclone this afternoon, beneath a
   remnant EML plume, which will result in MLCAPE of 1500-2500 J/kg.

   Surface heating/mixing and low-level convergence near the cyclone,
   in combination with divergence aloft in the exit region of the
   mid-upper jet, will all result in removal of convective inhibition. 
   Thunderstorm development is expected by about 20z near the surface
   low, with subsequent new storm development eastward near the KS/NE
   border.  Deep-layer southerly flow (effective bulk shear near 50 kt)
   and the moderate buoyancy will support supercells, along with
   substantial low-level shear/hodograph curvature.  Surface
   temperature-dewpoint spreads could become marginally large (near 20
   F) this afternoon, though steep low-midlevel lapse rate profiles
   will be favorable for vertical stretching and successive tornado
   formation with eastward-developing storms.  Very large hail and a
   few damaging gusts will also be possible.

   ...Western KY/IL/IN this afternoon/evening...
   Tropical depression Cristobal is moving north-northeastward just to
   the west of Saint Louis, and will continue toward WI/Upper MI
   overnight.  East of the cyclone center, low-mid 70s dewpoints are
   spreading northward into southern IL/western KY, and will reach IL
   this afternoon.  A belt of 40-50 kt low-midlevel flow around the
   eastern periphery of the system will contribute to sufficient
   vertical shear for rotating storms.  The primary uncertainty is the
   degree of surface heating/destabilization within the richer moisture
   plume where clouds are widespread, which will be necessary for the
   formation of more cellular convection that could evolve into small
   supercells with an attendant tornado and damaging wind threat.

   ...Eastern AR/northern LA to south TX this evening/early tonight...
   A strong late-season cold front will surge eastward-southeastward
   across AR/LA/TX through tonight.  The cold front will likely
   remained capped until this evening or early tonight, when it
   encounters richer low-level moisture and a broken band of storms
   could form on the boundary.  Isolated strong/damaging gusts will be
   the main threat.  Farther southwest, a cluster of storms could also
   form where the front interacts with the higher terrain in northeast
   Mexico, and some of this convection could spread into adjacent areas
   of south TX this evening/early tonight.

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