SPC AC 141245

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0745 AM CDT Fri Aug 14 2020

   Valid 141300Z - 151200Z

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS TODAY FROM
   EASTERN ND INTO MN...

   ...SUMMARY...
   Severe thunderstorms with damaging wind and hail, and perhaps a
   couple of tornadoes, will be possible from eastern North Dakota this
   morning into Minnesota this afternoon.  Additional severe storm
   development is expected this afternoon and evening from western Iowa
   into northwestern Kansas.

   ...MN to KS through early tonight...
   A midlevel shortwave trough over the western Dakotas will progress
   eastward to the upper MS Valley by tonight.  A surface cyclone near
   the SD/ND border will develop northeastward across northwestern MN
   in advance of the midlevel trough, as a trailing surface cold front
   moves southeastward across MN/northwestern IA/eastern NE/and
   northern KS by late evening.  Low-level ascent along the front will
   provide a focus for strong-severe thunderstorm development from mid
   afternoon through late evening.  The situation will be a little more
   complex farther north into eastern ND this morning and northern MN
   today, in response to ongoing convection.

   Storms across southeastern ND are expected to persist through the
   day across eastern ND/northwestern MN, near the path of the surface
   cyclone and midlevel jet.  Separate convection from central MN into
   southeastern ND has produced a cold pool/outflow boundary that will
   tend to demarcate the northern extent of the more substantial severe
   threat.  This boundary may try to retreat northward some today near
   the ND/MN border, though the cluster over south central ND will
   likely reach east central ND by mid morning, effectively limiting
   the time for air mass recovery farther north.  This morning cluster
   will move along the synoptic front/buoyancy gradient across ND, up
   to the northern extent of the outflow from the morning storms in MN.
    Damaging winds and large hail can be expected with this morning
   cluster.  The tornado threat will be modulated by the location of
   the outflow boundary, and appears more probable across parts of west
   central/northwestern MN as the low levels destabilize near and south
   of the outflow by early afternoon, and as vertical shear increases
   with the approach of the midlevel trough.

   By mid afternoon, convective inhibition should weaken in a narrow
   zone along the cold front from southwestern MN across eastern
   NE/northwestern IA into northwestern KS.  MLCAPE in excess of 3000
   J/kg and effective bulk shear of 30-35 kt, in combination with steep
   midlevel lapse rates and DCAPE at or above 1000 J/kg, will favor a
   mix of multicell clusters/line segments and some splitting
   supercells capable of producing damaging winds and large hail. 
   High-based storms farther south into the TX Panhandle may produce
   isolated severe outflow gusts this evening.

   ...Southern AR into parts of LA/MS today...
   An ongoing cluster of storms in southern AR, that originated in a
   warm advection zone in advance of a weak midlevel trough, should
   continue to spread southeastward on convective outflow today. 
   Moderate buoyancy/little convective inhibition, and a modest
   increase in vertical shear with the southeastward-moving midlevel
   trough, could maintain somewhat organized multicell clusters with an
   attendant threat for isolated wind damage through this afternoon.

   ..Thompson/Gleason.. 08/14/2020

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