SPC AC 260559

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1259 AM CDT Sun Jul 26 2026

   Valid 261200Z - 271200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR PARTS OF THE
   UPPER MIDWEST AND GREAT LAKES SOUTHWESTWARD INTO NEBRASKA...

   ...SUMMARY...
   Severe thunderstorms capable of large to very large hail, damaging
   winds (possibly 75+ mph), and potentially some tornado risk are
   possible from the upper Mississippi Valley and Great Lakes
   southwestward into portions of Nebraska, mainly this afternoon into
   tonight.

   ...Parts of the Upper Midwest/Great Lakes...
   An upper ridge will remain anchored from the Southwest into the
   central Rockies and High Plains through the period. Seasonably
   strong northwesterly flow aloft will overspread a very warm, moist,
   and unstable environment from parts of the Upper Midwest and Great
   Lakes into the central Plains. This will result in a conditionally
   favorable environment across a broad region, though with generally
   subtle forcing mechanisms, considerable uncertainty remains
   regarding storm evolution through the period. 

   Aside from any MCV influence on early-day convection, the most
   likely initiation zone for diurnal storm development currently
   appears to be from northern MN into WI, where one or more
   low-amplitude midlevel vorticity maxima may impinge upon the
   destabilizing environment. Initial supercell development would be
   possible in this area, posing a threat of large to very large hail,
   localized severe gusts, and potentially some tornado risk. Upscale
   growth into one or more intense southeastward-moving clusters with
   attendant severe-wind swaths would then be possible with time.
   However, some guidance remains relatively sparse with
   afternoon/evening development, resulting in uncertainty regarding
   coverage and favored corridors of potentially significant severe
   potential. Greater probabilities and an upgrade to Level-3/Enhanced
   Risk may eventually be needed, depending on how the uncertainties
   are resolved later today. 

   ...NE into adjacent parts of southeast SD and western IA...
   A somewhat separate area of potential severe-storm development is
   expected from parts of central NE into southeast SD. Initiation is
   expected near a weak surface trough as temperatures warm to near
   above 100 F and CINH is removed. MLCAPE of near/above 1500 J/kg and
   effective shear of 30-40 kt will favor development of a few
   organized cells and/or clusters. Severe gusts of 60-80 mph appear to
   be the most likely hazard within the hot/well-mixed environment.
   Isolated hail may also occur with any supercell, despite rather warm
   temperatures aloft.  

   ...Mid-Atlantic into the Carolinas/GA/north FL...
   A seasonably deep upper trough will persist across much of the
   eastern CONUS today. A modest increase in midlevel northwesterly
   flow is expected with time from the Mid-Atlantic into the Carolinas,
   GA, and north FL. 

   Relatively cool conditions, weak lapse rates, and the potential
   influence of smoke will temper destabilization across the Mid
   Atlantic. However, MLCAPE increasing to near 1000 J/kg amid 25-35 kt
   of effective shear may support occasional storm organization, with a
   primary threat of locally damaging wind. 

   Farther south, stronger heating/destabilization is expected across
   the Carolinas into GA/FL. Deep-layer flow/shear will be somewhat
   weaker compared to areas farther north, but may still be sufficient
   for transient storm organization and a localized damaging-wind
   threat. 

   ...Southern MT/northern WY into the Black Hills...
   High-based convection is expected to develop this afternoon along
   the northern periphery of the upper ridge, with the greatest
   relative coverage expected across parts of northern WY and southern
   MT. Buoyancy is expected to remain weak, but inverted-v profiles
   will support a threat of strong to localized severe gusts as storms
   move eastward towards the Black Hills before weakening this evening.

   ..Dean/Squitieri.. 07/26/2026

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