SPC AC 141947

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0247 PM CDT Thu May 14 2020

   Valid 142000Z - 151200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS EASTERN KANSAS
   INTO THE OHIO VALLEY...AND IN THE VICINITY OF NORTHWEST OKLAHOMA...

   ...SUMMARY...
   Isolated to scattered severe thunderstorms are possible later this
   afternoon into tonight from eastern Kansas into the Ohio Valley, and
   in the vicinity of northwest Oklahoma.

   ...Discussion...

   Only minor adjustments have been made to previous forecast which
   still appears on track.

   ..Dial.. 05/14/2020

   .PREV DISCUSSION... /ISSUED 1130 AM CDT Thu May 14 2020/

   ...KS/MO to the OH Valley this afternoon through tonight...
   A mainly zonal flow regime is present over the CONUS, with a
   stronger belt of flow from the northern Great Basin to the upper MS
   Valley and Great Lakes, and a more subtle southern stream across
   AZ/NM.  At the surface, a slow moving front extends
   east-northeastward from a cyclone in west central KS to southern IA
   and northern IL/IN.  Overnight and ongoing convection has introduced
   some convective outflow south of the front from northern MO into
   central IL.  Farther south in the open warm sector, remnant MCVs
   from overnight convection are moving east-northeastward (now located
   southwest of Tulsa and south of McAlester in eastern OK).

   A belt of 25-35 kt southwesterly low-level flow will be maintained
   through the afternoon from eastern OK into MO/IL/IN/OH, which will
   support continued weak low-level warm advection and moisture
   transport.  Flow aloft will remain relatively weak with little
   vertical shear above some low-level hodograph curvature.  This
   environment appears supportive of mainly multicell clusters and some
   transient supercells along the front and residual outflow boundaries
   this afternoon/evening from eastern KS into the OH Valley. 
   Convection will likely evolve into a larger band/line along the
   front and the develop southeastward and southward overnight on
   convective outflow.  The stronger storms overnight will likely be
   across MO/eastern KS, where a low-level jet will maintain an influx
   of richer moisture from the southern Plains.  Occasional large hail
   and damaging outflow winds will be the main threats with these
   frontal storms later this afternoon into tonight.  The tornado
   threat is more questionable based on the relatively weak deep-layer
   shear which will tend to limit storm longevity, and expected upscale
   growth into a line.

   ...West central/northwest OK border region this evening...
   The cold front/dryline triple point will likely sag southward to
   near or south of Gage by late afternoon.  Strong surface heating
   near and south of the triple point will occur this afternoon, with
   convective inhibition largely removed once surface temperatures
   reach 88-90 F (per the 12z AMA sounding).  Boundary-layer dewpoints
   will likely mix into the upper 50s to lower 60s just east of the
   dryline, but this will still support MLCAPE of 2500-3000 J/kg. 
   Isolated thunderstorm development will be possible near the triple
   point this evening, by which time deep-layer vertical shear should
   have increased some with the approach of embedded speed maxima from
   AZ/NM.  Relatively straight hodographs would favor splitting
   supercells with a primary threat of large hail, prior to convection
   weakening early tonight as convective inhibition increases. 

   ...Northwest/north central MN this afternoon/evening...
   A small midlevel low near the ND/MB border will move eastward to
   northern MN this afternoon/evening, along with a weak surface
   reflection.  Boundary-layer dewpoints of 50-52 F and some surface
   heating in proximity to the midlevel cold pool (-24 C at 500 mb)
   could result in SBCAPE approaching 500 J/kg.  The weak
   destabilization in combination with ascent in advance of the
   midlevel low and along an associated surface trough could support a
   few low-topped thunderstorms with hail close to 1".

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