Strengthening Boundary Sets Up Supercell Hail, Tornado Threat in Minnesota-North Dakota — SevereWX

Strengthening Boundary Sets Up Supercell Hail, Tornado Threat in Minnesota-North Dakota

A stalled but beefing-up low-level weather boundary stretching from north central Minnesota into southeast North Dakota is primed to ignite strong thunderstorms this evening. The Storm Prediction Center's Mesoscale Discussion 1829 flags a 60% chance of a tornado watch as conditions align for supercell development between 7-9 PM CDT.

Under a cap from warm elevated mixed layer air, steep mid-level lapse rates are building moderate instability in a narrow corridor. A 30-40 kt southwesterly low-level jet on the boundary's west side pairs with 50-70 kt upper-level flow, creating a sheared environment ripe for rotating storms.

Key Threats:

• Hail: Most probable 1.00-1.75 inches (golf ball to ping pong ball size)
• Winds: 55-70 mph gusts
• Tornadoes: Up to 90 mph (low-end EF2 intensity)

Stronger lift lags west of the boundary, so storms might hug the cool side or get undercut quickly. Even so, thermodynamic profiles should sustain large hail into the night before a frontal wave pushes the line east.

This setup affects parts of north central through west central Minnesota and adjacent southeast North Dakota. Check SPC graphics for the exact lat/lon box.

Stay Prepared: Monitor radar closely this evening. Keep a NOAA Weather Radio handy, know your safe room, and have a severe weather plan ready to act fast if warnings fire.