SPC AC 261233

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0733 AM CDT Thu Jun 26 2025

   Valid 261300Z - 271200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON
   ACROSS FAR SOUTHEAST MN...NORTHERN IA AND SOUTHERN WI...

   ...SUMMARY...
   A few tornadoes and isolated wind damage will be possible this
   afternoon from northern Iowa and southwest Minnesota into southwest
   Wisconsin. Isolated wind damage will be possible across a broad area
   of the eastern Plains, Ohio Valley, Mid-Atlantic, the Southeast and
   Montana.

   ...Southern MN/IA/Southern WI...
   Early morning radar and satellite imagery show a well-defined MCV
   moving northeastward into eastern NE. Surface analysis reveals a low
   over eastern NE, which is associated with this vorticity maximum as
   well. A stationary boundary extends northeastward from this low
   through northwestern IA to another low in the MN/IA/WI border
   intersection vicinity. This boundary, which separates a moist
   airmass characterized by 70s dewpoints from a more continental
   airmass with low 60s dewpoints, could act as a favored corridor for
   northeastward progress of the surface low throughout the day. At the
   same time, strengthening southerly low-level flow will increase the
   low-level moisture advection south of this boundary, resulting in
   some tightening of this boundary throughout the day. Some guidance
   suggests this boundary could move slightly northward as a warm front
   as well. This low-level moisture advection will also help offset
   surface dewpoint reductions due to mixing, with dewpoints likely
   remaining in the 70s along and south of the boundary. Strong heating
   of this moist airmass will bring temperatures in the upper 70s/low
   80s, fostering airmass destabilization and strong buoyancy by the
   early afternoon.

   Thunderstorm development is expected as the approaching vorticity
   maximum and associated surface low interact with this unstable
   airmass, with initiation occurring both near the surface low as well
   as farther east amid the convergence along the warm front. The
   development near the low should becoming linear quickly while the
   activity along the front should remain more cellular longer. The
   initial/more discrete storms could be supercells with the potential
   to produce a few tornadoes within the moderately sheared and
   vorticity rich environment along the front. Damaging gusts will be
   possible with the linear segments as well, particularly in close
   vicinity to the surface low where mesoscale circulations could
   augment updrafts and downdrafts.

   ...Central/Eastern KS into Western/Central OK...
   Recent surface analysis reveals weak surface troughing to the south
   of a low over eastern NE. This troughing will likely shift eastward
   as its parent low progresses northeastward, with convergence along
   this boundary contributing to thunderstorms across central and
   eastern KS. The character of the boundary will become more diffuse
   with southern extent, but modest low-level confluence should still
   be enough to support afternoon thunderstorm development. Vertical
   shear will be weak through this entire corridor, but thermodynamic
   profiles will favor strong downdrafts and the potential for isolated
   strong-severe outflow gusts for a few hours this afternoon/evening.

   ...Southeast...
   Overnight convection has resulted in extensive cloudiness across
   much of the region this morning. Even so, ample low-level moisture
   remains in place and the airmass is expected to destabilize by the
   early afternoon amid strong heating. Initial development appears
   most likely near the westward progressing outflow moving across MS,
   with additional development later near a convectively generated
   vorticity maximum moving across central GA. Widespread storms are
   also expected across FL as an upper low drifts slowly
   west-northwestward. Shear will be weak areawide and a largely
   disorganized storm mode is anticipated. Surging outflow is possible
   with the strongest storms, fostering the potential for damaging
   gusts and also contributing to additional storm development. Several
   forward-propagating clusters are possible although their location,
   strength, and longevity are uncertain, precluding any increased
   severe probabilities with this outlook. 

   ...MT this afternoon/evening...
   A subtle midlevel trough and associated/diffuse front will move
   across the northern Rockies this afternoon into tonight.  Deep
   mixing and inverted-V profiles will favor some potential for
   strong-severe outflow gusts with scattered high-based thunderstorms
   along and ahead of the diffuse front this afternoon into this
   evening.

   ...OH Valley into the Mid-Atlantic this afternoon...
   Scattered thunderstorms are expected again this afternoon as the
   airmass destabilizes amid strong daytime heating and ample low-level
   moisture. Residual boundaries from prior convection, and terrain
   circulations will act as favored areas for initiation. Vertical
   shear will be weak, but steep low-level lapse rates and
   precipitation loading could support isolated wind damage with
   downbursts from mid afternoon into the evening.

   ..Mosier/Wendt.. 06/26/2025

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