Bigger Than a Baseball: Twin Cities, Eau Claire, and Madison Face a Very Favorable Hail Setup on Monday as the Atmosphere Supports Egg-Sized Hail If Storms Get Rotating
TWIN CITIES, MINNESOTA — If you live in the Twin Cities, Eau Claire, or Madison, forecasters have a simple and direct message for you heading into Monday April 13, 2026 — put your car in the garage or under the carport today. A very favorable hail setup is in place for Monday, and while only a few thunderstorms are expected to form, the ones that do could produce hail bigger than baseballs.
A Rare and Dangerous Hail Setup for Monday
The SPC Conditional Max Hail Potential guidance for Monday April 13, 2026 identifies one of the more serious hail setups seen this season across the Upper Midwest. The atmosphere is not expected to produce widespread storms — but that is not the point. The storms that do manage to develop and sustain rotation carry the potential for extremely large and destructive hail.
Forecasters describe this as a very favorable hail setup — a phrase that reflects just how loaded the atmosphere is for large hail production if the right storm can get going.
What Size Hail Is Possible and Where
The SPC Conditional Max Hail Potential map lays out the threat in clear terms across two overlapping zones.
| Hail Size | Zone Covered |
|---|---|
| Egg-sized hail | Core zone covering the Twin Cities, Eau Claire, Madison, Sioux Falls, Des Moines, Davenport, Milwaukee corridor |
| Baseball-sized hail — very isolated | Within the egg-sized zone — isolated supercells only |
| Quarter-sized hail | Expanding zone east toward Marquette, Sault Ste. Marie, Alpena, Saginaw, Cadillac, and into Michigan |
The egg-sized hail zone forms the bullseye of Monday’s threat, covering a large oval stretching across Minnesota, Wisconsin, and into Iowa and Illinois. Sitting inside that zone is an even more concentrated area where very isolated baseball-sized hail is possible — the maximum that the atmosphere can support if a rotating thunderstorm becomes established.
To the east, a broader quarter-sized hail zone extends into Michigan, covering areas including Marquette, Sault Ste. Marie, Alpena, Saginaw, Cadillac, and reaching toward Detroit, Toledo, and Cleveland at the southern edge.
Understanding What This Guidance Actually Means
The SPC is clear about what this product represents — and what it does not. This map shows the ballpark maximum hail size the atmosphere can support if a rotating thunderstorm becomes established. It does not depict the likelihood or expected areal coverage of hail. Coverage will remain isolated to scattered.
That distinction matters. Most people in the zone will not see giant hail on Monday. But for the unlucky few who find themselves under a storm that does get rotating and sustaining — the hail potential is extreme. Egg-sized hail is roughly 1.75 inches in diameter. Baseball-sized hail reaches 2.75 inches. Both are capable of destroying vehicles, shattering windows, damaging roofs, and injuring anyone caught outdoors.
Cities That Need to Be on Alert Monday
| City | Hail Threat Zone |
|---|---|
| Twin Cities, Minnesota | Egg-sized — very isolated baseball possible |
| Eau Claire, Wisconsin | Egg-sized — very isolated baseball possible |
| Madison, Wisconsin | Egg-sized — very isolated baseball possible |
| Milwaukee, Wisconsin | Egg-sized zone |
| Sioux Falls, South Dakota | Egg-sized zone |
| Des Moines, Iowa | Egg-sized zone |
| Davenport, Iowa | Egg-sized zone |
| Marquette, Michigan | Quarter-sized zone |
| Sault Ste. Marie | Quarter-sized zone |
| Alpena, Michigan | Quarter-sized zone |
| Saginaw, Michigan | Quarter-sized zone |
| Cadillac, Michigan | Quarter-sized zone |
| Detroit, Michigan | Quarter-sized outer zone |
| Toledo, Ohio | Quarter-sized outer zone |
| Cleveland, Ohio | Quarter-sized outer zone |
What You Should Do Before Monday Arrives
The advice here is practical and specific — and it applies most urgently to residents of the Twin Cities, Eau Claire, and Madison who sit in the core of the egg-sized and isolated baseball hail zone.
- Put your vehicle in the garage or under a carport before Monday — hail damage to vehicles is instant, costly, and entirely preventable with covered parking
- Do not wait for a warning to take action — by the time a severe thunderstorm warning is issued, storms are already producing hail
- Stay indoors if storms develop — egg-sized and baseball-sized hail is large enough to injure anyone caught outside
- Monitor weather alerts closely throughout Monday — storm coverage will be isolated, meaning warnings can be highly localized and fast-moving
Monday Hail Threat at a Glance
| Factor | Details |
|---|---|
| Valid date | Monday April 13, 2026 |
| Guidance type | SPC Conditional Max Hail Potential |
| Storm coverage expected | Only a few thunderstorms — isolated to scattered |
| Maximum hail size possible | Baseball-sized — very isolated |
| Primary hail size zone | Egg-sized across Twin Cities, Eau Claire, Madison corridor |
| Eastern hail zone | Quarter-sized across Upper Michigan and Great Lakes |
| Setup description | Very favorable hail environment |
The Bottom Line: Few Storms, But the Wrong One Could Be Devastating
Monday is not a widespread severe weather outbreak. Storm coverage will be limited — only a few thunderstorms are expected to form across the region. But the atmospheric setup is so favorable for large hail that the storms which do develop and rotate have the support to produce egg-sized to isolated baseball-sized hail — the kind that totals cars and punches through roofs in seconds.
Twin Cities, Eau Claire, and Madison residents should treat Monday as a high-hail-risk day regardless of how calm the morning looks. Get vehicles covered, monitor alerts, and be ready to take shelter quickly if warnings are issued in your area.
Stay with CabarrusWeekly.com for live Monday severe weather updates, hail reports, and storm warnings across the Twin Cities, Upper Midwest, and Great Lakes region as the day unfolds.
