SPC AC 081626

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1126 AM CDT Mon Jun 08 2020

   Valid 081630Z - 091200Z

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS LATE THIS
   AFTERNOON INTO EARLY TONIGHT FOR PARTS OF THE CENTRAL AND NORTHERN
   PLAINS...

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON
   ACROSS EASTERN AND NORTHERN MS...WESTERN AL...AND SOUTHWESTERN TN...

   ...SUMMARY...
   Scattered severe thunderstorms are likely late this afternoon into
   tonight across parts of Nebraska and the eastern Dakotas into
   western/northern Minnesota. The remnants of Cristobal may pose a
   risk for a few tornadoes across parts of Mississippi, Alabama, and
   the Mid-South region.

   ...Central/northern Plains late this afternoon into tonight...
   As part of an amplified pattern across the CONUS, the primary
   midlevel trough over NV/UT will progress slowly eastward to
   CO/northern NM overnight.  Expect a slow-moving surface cold front
   to stall today across NE, in response to lee cyclogenesis across the
   central High Plains, in advance of the UT/NV midlevel trough.  This
   front will serve as the primary focus for severe storm development. 
   Beneath a remnant EML, boundary-layer dewpoints will range from the
   low-mid 60s along the front in central NE to the upper 60s along the
   eastern ND/MN border region.  Surface heating/mixing in the warm
   sector, along with low-level ascent along the front, will support
   thunderstorm development late this afternoon into this evening from
   central NE to the eastern Dakotas/western MN.

   MLCAPE is expected to reach the 2000-3000 J/kg range by late
   afternoon along the front, in an environment with effective bulk
   shear in excess of 40 kt.  Largely straight hodographs with
   relatively weak low-level shear/hodograph curvature will support
   supercells with the primary threats of large hail initially.  Some
   upscale growth and increase in the damaging-wind threat is expected
   this evening due to storm interactions, with deep-layer
   south-southwesterly flow will largely parallel the slow-moving
   front.  The overall tornado threat is more in question given the
   weak low-level shear this afternoon.  A relatively greater tornado
   threat is possible in the greater low-level moisture with initial
   storm development in the vicinity of northwest MN this evening, and
   across central NE where some backing and strengthening of low-level
   flow is expected by late evening/early tonight, east of the
   deepening lee cyclone.

   ...MS/AL/TN/AR/MO through tonight...
   The weakening remnants of tropical cyclone Cristobal will continue
   to move generally northward across the Ark-La-Miss to southern MO
   overnight, with a gradual acceleration in response to an approaching
   midlevel trough over the central High Plains.  Regional 12z
   soundings revealed 500 mb temperatures of -1 to -2 C with the warm
   core system, which will tend to limit buoyancy in proximity to the
   cyclone core.  Surface heating in cloud breaks in the vicinity of
   the main eastern band (near the MS/AL border), which is also
   coincident with a belt of 40-50 kt low-midlevel flow, could support
   a isolated supercells this afternoon.  Observed and forecast
   hodographs only show modest low-level curvature/SRH, so it appears
   the tornado threat can be characterized as somewhat marginal.  

   The tropical air mass across the Gulf coast states will slowly
   spread northward with Cristobal, replacing the relatively dry air
   now present to the north of TN.  It is not clear if the increases in
   moisture/weak buoyancy and vertical shear will be sufficient for
   rotating storms on the north-northeast periphery of the circulation
   this afternoon into southeast MO.  After the loss of daytime
   heating, the threat for supercells should diminish slowly, but not
   completely end in the moist environment.

   ..Thompson/Lyons.. 06/08/2020

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