SPC AC 261730

   Day 2 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1230 PM CDT Fri Jul 26 2024

   Valid 271200Z - 281200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS
   CENTRAL/EASTERN ND INTO FAR NORTHWEST MN...

   ...SUMMARY...
   Scattered severe thunderstorms are likely across portions of the
   northern Plains vicinity on Saturday.

   ...Synopsis...
   Upper troughing is expected to extend from the northern/central
   Canadian Prairie Provinces southwestward into northern/central CA
   early Saturday morning. Two primary shortwave troughs will be
   embedded within this troughing, one over the northern/central
   Canadian Prairies and the other over northern CA. Both shortwaves
   are expected to progresses east-northeastward throughout the day
   while losing amplitude. Eastward progress of this systems will be
   slowed by the Rex block downstream, with the southern cyclone
   initially over northeast OK/southeast KS and the northern
   anticyclone over Lake Michigan. This Rex block is forecast to break
   down under the influence of the western troughing, with the upper
   low drifting northeastward into southern MO and the upper ridge
   shifting eastward over the Lower Great Lakes by early Sunday. 

   Surface pattern is forecast to feature an eastern CONUS ridge,
   initially centered over the Lower Great Lakes but extending
   southward into the Southeast. This ridging is expected to remain
   largely in place, while lee surface troughing sharpens across the
   High Plains and a cold front associated with the Canadian Prairie
   shortwave trough moves into the northern Plains. Thunderstorm
   development is anticipated along the cold front across ND Saturday
   evening. Storm development is also anticipated farther southwest
   across the central Rockies, with the resulting storms then tracking
   eastward into the central High Plains. 

   ...Northern Plains..
   Showers and thunderstorms will likely be ongoing early Saturday
   morning from the eastern Dakotas int northwest MN, remnant from
   overnight development across the western/central Dakotas. This
   activity will likely be weak, but cloud cover and associated outflow
   could act to provide the surface boundaries needed to provide the
   impetus for additional storms during the afternoon/evening.
   Large-scale forcing will be weak, but low-level convergence and
   ample low-level moisture could still result in thunderstorm
   initiation. Given the steep low-level lapse rates and high cloud
   bases, damaging gust will be the primary threat. Even so, some hail
   is possible with the early, more cellular storms. A tornado or two
   is possible as well if the boundary is sharp, with surface winds
   backing in its vicinity. Mesoscale factors will play a large role in
   determining the storm coverage and associated severe potential,
   which merits keeping low severe probabilities with this outlook
   given the forecast range.  

   Farther east, thunderstorm development appears likely along the
   southeastward-progressing cold front expected to move across the
   western Dakotas during the late afternoon. Ample low-level moisture
   will support airmass destabilization despite strong mixing, and
   robust updrafts are likely within the initial development. Hail is
   possible early, with a quick transition to outflow-dominant
   structures anticipated. Highest coverage is expected across ND,
   which corresponds to the greatest severe thunderstorm potential as
   well. Storm longevity will be limited by the onset of nocturnal
   cooling, which should lead to relatively quick low-level airmass
   stabilization.  

   ...Northern Great Basin into the central Rockies and central High
   Plains...
   A belt of enhanced mid-level flow is forecast to stretch from the
   base of the northern/central CA shortwave trough mentioned in the
   synopsis into the northern Plains. The CA shortwave is expected to
   progress northeastward throughout the period, with a subtle,
   convectively enhanced lead shortwave trough likely proceeding it
   across the central Rockies. Large-scale ascent attendant to these
   shortwaves coupled with increased mid-level moisture and deep
   boundary-layer mixing will support thunderstorms across much of the
   region, beginning over the higher terrain and then eventually
   spreading into the High Plains. Gusty outflow winds could accompany
   of any of the stronger, more persistent storms. Coverage of these
   strong storms may be high enough to merit greater severe
   probabilities in later outlooks.

   ..Mosier.. 07/26/2024

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