Severe weather moving into Ann Arbor shortly

As promised, a cold front moving through the region is bringing with it strong thunderstorms, hail, damaging winds, and tornados.

A powerful line of storms (radar image below) stretches from Jackson west to northwest of Kalamazoo, and the humid air will continue to fuel storm development until 1 or 2 am.

The storm currently over Jackson is currently severe-warned and will continue toward Ann Arbor in the next 30-40 minutes. It appears to be weakening very slightly, but severe activity behind that continues to move east toward us.

It does appear that the furthest-west activity is slightly north of Ann Arbor and if it continues due east, it ought to remain mostly over Livingston County. But it is too early to say that with certainty; there’s plenty of warm, humid air to go around, and it appears that storms are forming along I69 between Coldwater and Marshall; if those continue to develop they’ll certainly hit us.

It is hard to predict with certainty whether any of these storms will be severe when they hit us. But we will see some strong storms in Ann Arbor tonight. Generally speaking, they will come with lots of lightning, some hail, and strong (possibly damaging) winds. Rain will be moderate, heavy, or locally torrential.

Storms ahead of this front have earlier produced strong low-level rotation and possible tornados, and a tornado watch remains in effect until 3am. Where the front north of M59 produced many severe cells and tornado warnings, it does appear the storms headed toward us are less happy to produce strong rotation, but of course this could change and we should remain alert until the tornado watch is cancelled.

Tune to local emergency broadcasters for reliable updates. (Follow ArborWX too, but ArborWX might fall asleep.)

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Significant severe weather expected in SE Michigan this afternoon/evening/tonight

There is a significant chance of severe weather this afternoon into tonight across southeast Michigan. A first wave of storms will occur as a warm front lifts through the region, and a second wave as a corresponding cold front moves through later tonight.

This afternoon and evening, expect strong and potentially severe thunderstorms with heavy rain, damaging wind gusts (up to 60mph), and localized hail up to 1″ in diameter.

Tonight (after 8pm until early morning), expect yet stronger storms with more intense wind gusts (up to 70mph), heavy rain, and localized golf-ball-sized hail. This second wave of storms comes with a tornado risk as well; there is a relatively significant chance for tornados to form in SE Michigan. The risk is greatest north of M-59; NWS reports the risk north of M59 is from 9pm-2am and south of M59 (so, for Ann Arbor) is from 11pm-4am.

Skywarn spotter activation is likely with these storms.

As always, it is not possible to predict ahead of time exactly when a storm will strike Ann Arbor specifically; these predictions are for the larger SE Michigan region at this time.

Tornado watch issued including Ann Arbor until 8pm

Update: as of 5:33pm this tornado watch has been cancelled.



A tornado watch has been issued for our area, effective immediately until 8pm.

This means that the storms moving into the area this afternoon will provide conditions ideal for the formation of tornados.

You should continue monitoring local media for any severe storm or tornado warnings. (Here’s a list of Washtenaw County’s emergency broadcasters.)

And you should prepare by reviewing these tornado safety tips.

Thunderstorms expected as cold front moves through; severe storms are possible

Update 5:37pm: heavy cloud cover helped prevent this system from developing severe storms in Ann Arbor. The city will see light rain on and off into the evening.

As a cold front moves through southern Michigan this afternoon into the evening, we will see rain and many thunderstorms scattered across the region.

Some of these storms will be strong, and the National Weather Service has rated our area at an “enhanced” risk of severe storms for today. Image follows.

(That’s right in the middle of the scale: it goes “none”, “marginal”, “slight”, “enhanced”, “moderate”, “high”.)

Day 1 Categorical Outlook May 11


Along with these storms, we can expect strong winds and localized heavy rainfall. Damaging hail is possible. There is a very small chance of tornados predicted with today’s storms.

The outlook for damaging winds today:


The thunderstorm outlook for today shows a high potential for storms from 4-8pm:


Update: these following thunderstorm outlooks became outdated while this post was being written. Finally, the thunderstorm outlooks for noon-4pm and then 4-8pm follow, indicating late afternoon is when we’re likely to see the stronger storms:




Washtenaw County warning siren testing to resume March 7

I previously reported on the imminent testing of the city’s siren system; Washtenaw County will resume testing its siren system (which is independent of the city’s system) this month as well.

The county’s sirens are tested at noon on the first Saturday of every month from March through October. This means the first test will be at noon this Saturday, March 7.

Except for scheduled tests, the county’s sirens will be activated when:

  • The National Weather Service has issued a tornado warning
  • A severe thunderstorm has been detected with damaging winds in excess of 70 MPH
  • A hazardous materials accident requires immediate protective action by the public
  • An attack on the United States is imminent, underway or has recently occurred

If you hear sirens and you’re not sure whether it’s a scheduled text, tune into one of the county’s emergency broadcasters.