SPC AC 090059

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0759 PM CDT Fri Aug 08 2025

   Valid 090100Z - 091200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM EASTERN SD
   INTO MN AND NORTHWEST WI...AND ALSO ACROSS SOUTHWEST SD AND WESTERN
   NE...

   ...SUMMARY...
   Scattered severe thunderstorms with damaging winds, large hail, and
   possibly a tornado are expected to develop this evening and tonight
   across parts of the Upper Midwest and the central High Plains.

   ...Eastern Dakotas into MN/northwest WI...
   Scattered to widespread storm development is still expected later
   this evening from the far eastern Dakotas into MN, as a seasonably
   deep mid/upper-level shortwave trough and attendant cold front
   impinge upon a strongly unstable environment. A few supercells could
   evolve initially within a moderately sheared environment, with a
   threat of hail and possibly a tornado. Deep-layer flow/shear
   generally parallel to the front will likely result in a quick
   transition to a cluster or linear mode. This could lead to an
   increasing threat for damaging wind, though there may be some
   tendency for convection to become slightly anafrontal with time. 

   Guidance suggests the greatest relative threat for more organized
   upscale growth will be from central into northeast MN, along a
   diffuse surface boundary. The late timing and the effects of
   nocturnal low-level stabilization results in some uncertainty
   regarding the magnitude of the severe-wind threat, but a swath of
   damaging wind remains possible into the overnight hours.  

   ...Central Plains vicinity...
   Development of a supercell or two remains possible this evening
   within a post-frontal regime from southwest SD into western NE,
   though coverage remains uncertain. Elongated hodographs would
   support a hail threat with any sustained cells, with localized
   severe gusts also possible. 

   Some recent runs of the HRRR suggest post-frontal development
   overnight across parts of southeast WY and northeast CO. While this
   scenario is uncertain, the environment will be favorable for
   isolated hail and strong gusts if storms develop. 

   A nebulous but potentially organized severe threat also remains
   evident overnight across parts of NE into northern IA, within a
   favorably unstable and modestly sheared environment. Strong elevated
   storms will be possible as the front moves into the region, with
   some threat for hail and localized damaging winds. Any organized
   clustering could result in a locally greater damaging-wind threat.

   ...Northern Lower MI...
   A strong storm or two remains possible this evening across northern
   Lower MI, before convection wanes later tonight as CINH increases.
   Steep lapse rates, moderate buoyancy, and around 30 kt of effective
   shear (as noted on the 00Z APX sounding) could continue to support a
   threat of isolated hail and strong gusts before storms diminish with
   time.

   ..Dean.. 08/09/2025

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