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Update: these following thunderstorm outlooks became outdated while this post was being written.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.

Snow Condition Yellow

Washtenaw County is now at Snow Condition Yellow. Here’s what that means, and what we’ll be dealing with for the rest of this storm.

We’ve been under a winter storm warning since yesterday. That means “At least 6 inches of snow over a 12 hour period &/or significant amounts of freezing rain and gusty winds can be expected soon.” Winter storm advisories, watches, and warnings are issued by the National Weather Service in Detroit.

Washtenaw County’s Emergency Services Division will sometimes issue local travel bulletins. Snow Condition Yellow, which we’ve been in since about 5pm, means “Hazardous driving conditions are widespread with heavy snow or ice, drifting, and limited visibility. Traffic is moving at reduced speeds with major highways being maintained in fair condition, but local roads may be impassable. Motorists are urged that if they must drive, use extreme care and allow for a significant drive time.”

Basically: your local roads are going to be nearly impossible, and highways only just usable. Blowing snow and heavy ice are making driving anywhere now dangerous. Do not drive unless you absolutely must, and be extremely cautious if you do. We’re in Snow Condition Yellow until noon tomorrow.

For those curious, all this information comes straight from the county’s website. You can also learn what Snow Condition Red is there.

Now, to the forecast. As of 5pm, according to the county, we’ve seen more than 6 inches of snow, blowing snow is common, and “numerous” accidents have been reported. The NWS predicts 6 to 8 more inches before the storm ends, around sunrise on Monday; snowfall rates near 1 inch per hour are expected. Winds will persist between 20-30 miles per hour.

Please, everyone, stay safe. The roads really are in bad shape.

We’ll continue monitoring the storm here at ArborWX HQ and will post if it gets worse.

A Rainy, Windy Christmas

The winter storm we discussed previously is close enough now for the NWS to make some predictions. I’ll recap what we can expect over the next several days:

Starting tonight, we’ll see rain showers and cloudy, foggy conditions. Wednesday — Christmas Even — will be quite rainy, with a high temperature in the upper 40s or low 50s. Wednesday will also see wind start to pick up, and as we move into Wednesday night it’ll be rainy and wind gusts could reach 40-45 mph. Wednesday night it’ll be cooler; we might get some light snow overnight.

Christmas Day, we shouldn’t see much precipitation, but it’ll be breezy and cooler, with temperatures in the 30s.