SPC AC 280559

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1259 AM CDT Mon Apr 28 2025

   Valid 281200Z - 291200Z

   ...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS FOR SOUTHERN
   MINNESOTA...NORTHERN IOWA...AND WESTERN WISCONSIN...

   ...SUMMARY...
   Multiple corridors of severe thunderstorms are expected across the
   Upper Midwest later today into tonight, with a regional severe
   weather outbreak possible. The most dangerous period is likely
   during the late afternoon and evening when strong tornado potential
   should be maximized. Scattered large to very large hail and damaging
   winds are likely as well.

   ...Synopsis...
   A positively tilted mid/upper-level shortwave trough, with several
   embedded vorticity maxima, will move east-northeast through the day
   across the Great Plains and Upper Midwest. The southwest portion of
   the large-scale trough and an embedded midlevel cyclone will remain
   in place near the Four Corners through most of the period. A strong
   midlevel jet (70+ kt at 500 mb) will move from the central Plains
   toward the upper Midwest/Great Lakes later today into this evening.
   The primary surface cyclone will move from the eastern Dakotas
   toward the upper Great Lakes, as a trailing cold front moves through
   parts of the Great Plains and eventually the Upper Midwest. By late
   afternoon, a dryline will extend from near the MN/IA border
   southwestward into the southern High Plains. 

   ...Upper Midwest...
   A regional severe weather outbreak still appears possible across the
   Upper Midwest, with a threat of strong tornadoes, very large hail,
   and swaths of damaging winds. No major changes have been made to the
   Moderate and Enhanced Risk areas. 

   Extensive elevated convection and a possible MCS will likely be
   ongoing at the start of the forecast period across parts of ND/MN,
   and may tend to redevelop through the day. This could slow the
   northward advance of the warm front to some extent, but 60s F
   dewpoints are expected reach at least central MN into northern WI by
   mid/late afternoon. 

   South of the warm front and east of the dryline, the environment is
   expected to become increasingly volatile through the afternoon, with
   strong instability (MLCAPE near/above 3000 J/kg) and deep-layer
   shear, and a persistently intense low-level jet that will maintain
   very favorable low-level shear/SRH. This environment will be
   conditionally favorable for long-track supercells with
   strong/intense tornado potential. 

   Uncertainty remains regarding the evolution of diurnal convection
   across the warm sector. Guidance generally suggests that
   surface-based storms will develop near the surface low and along the
   prefrontal trough/dryline across southern MN, which could evolve
   quickly into a cluster or linear mode, though the environment would
   still support embedded supercell potential with all severe hazards
   possible. If development in this area is able to remain
   semi-discrete, then a couple long-track tornadic supercells could
   occur. 

   Farther south into IA, stronger heating/mixing is expected near the
   dryline, though large-scale ascent and low-level convergence may be
   somewhat weaker compared to areas farther north. While guidance
   varies regarding the potential for development across IA during the
   afternoon, any supercell that can initiate and be sustained could
   become long-tracked within the expanding and very favorable warm
   sector, posing a threat for strong to intense tornadoes and very
   large hail. 

   As the surface low and related boundaries move eastward, organized
   convection may develop in place and/or spread into parts of WI, with
   a threat of all severe hazards and some strong-tornado potential. 

   Farther west, a couple of supercells may develop in the region
   between the prefrontal trough/dryline and cold front, and pose a
   threat of large hail and locally damaging gusts as they move across
   northeast NE/southeast SD into parts of MN/IA. 

   ...Parts of KS/MO into the Southern Plains...
   While large-scale ascent will be comparatively weaker from KS/MO
   into the southern Plains, isolated to widely scattered storm
   development will be possible within a weakly capped environment.
   Instability and deep-layer shear will both be moderate to strong by
   late afternoon into the evening, and a few supercells may develop
   near the dryline. Large to very large hail and locally damaging
   winds will likely be the initial primary hazard, but increasing
   low-level SRH by early evening will result in some tornado threat as
   well. Additional strong to locally severe storm development will be
   possible overnight near the advancing cold front, aided by a
   continued nocturnal strengthening of the low-level jet.

   ..Dean/Weinman.. 04/28/2025

   CLICK TO GET WUUS01 PTSDY1 PRODUCT

   NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1300Z