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.

Clarifying: excessive heat warning vs. heat advisory

For those curious, these are the criteria used in SE MI for determining whether extreme heat warrants a heat advisory or an extreme heat warning:

  • Excessive Heat Watch – Issued when the Heat Index (HI) may be at least 105° within the next 2 to 3 days.
  • Heat Advisory – Issued when the HI is expected to be at least 100° for 3 hours or more. Can be issued with lower criteria with successive days heat.
  • Excessive Heat Warning – Issued when the HI is expected to be at least 105° for 3 hours or more. Can be issued with lower criteria with successive days heat.

Source: Heat Awareness Day 2012 information, which also includes some other useful heat-related information.

(Thanks to @ryanvis for pointing me to the relevant document)