Air quality alert until 6 a.m. Friday

It’s only mid-May and we’ve already seen our first statewide air quality alert for Minnesota. The alert also includes most of western and southern Wisconsin.

Here are the details on the air quality alert for Minnesota from the Minnesota Pollution Control Agency.

The Minnesota Pollution Control Agency (MPCA) has issued an air quality alert for the entire state of Minnesota. The alert runs until Friday, May 19, at 6 a.m.

A band of very heavy ground-level smoke from wildfires in northern Alberta and Saskatchewan is currently moving along a cold front in northwestern Minnesota. The smoke will continue to move south and east and eventually impact the entire state of Minnesota. The smoke should clear rapidly overnight into Friday morning.

Fine particle levels are expected to reach the red air quality index (AQI) category, a level considered unhealthy for everyone, across all but far eastern Minnesota. This area includes The Twin Cities Metropolitan Area, St. Cloud, Mankato, Moorhead, East Grand Forks, Roseau, Bemidji, Alexandria, Marshall, Ortonville, Worthington and the tribal nations of Red Lake and Mille Lacs. In the red area, everyone should avoid prolonged time outdoors.

Fine particle levels are expected to reach the orange AQI category, a level considered unhealthy for sensitive groups, across southeastern, northeastern, and far east central Minnesota. This area includes Rochester, Duluth, Ely, International Falls, Two Harbors, and the tribal nations of Fond du Lac and Grand Portage. In the orange area, sensitive groups should avoid prolonged time outdoors.

Smoke front

So why did the smoke reach ground level in Minnesota Thursday? It’s because of sinking air behind a cold front that moved through our state. That subsidence dragged down the smoke that was elevated several thousand feet above us on Wednesday.

This cross-section of a thunderstorms-driven gust front shows the same basic principle of descending air behind a cold frontal passage.

Because the smoke density increases rapidly with the frontal passage, it’s essentially a smoke front. Notice how the leading edge of the higher unhealthy smoke concentration moved into the Twin Cities area Thursday afternoon.

Air quality across Minnesota will improve quickly Friday as the back edge of this current smoke plume is pushed away. Here’s more detail from Thursday’s air quality forecast discussion from the MPCA.

An Air Quality Alert is in effect for the entire state of Minnesota, and runs through 6 a.m. Friday. A cold front stretching from International Falls to Worthington is moving east today. Heavy smoke behind the front moved into western Minnesota overnight and air quality has deteriorated across this region. The smoke will continue to move southeast throughout the day, reaching Brainerd this morning and the Twin Cities by midday. Smoke will eventually reach Rochester and southeast MN this afternoon. Fine particle levels may reach the Red (unhealthy) category for most of the state today. Brief periods of fine particle spikes into the Purple (very unhealthy) category are possible across western MN. The end of this smoke band will reach northwest MN by midday and air quality will begin to improve from northwest to southeast. The smoke should exit the state by tomorrow morning and air quality should improve back into the Green category statewide tomorrow, as high pressure moves into the state. Air quality should remain in the Green category statewide Saturday.

Beautiful weekend ahead

This weekend looks like the best weather weekend of the year so far for Minnesota. But first, we get a blustery cooler Friday. Northwest winds will gust to at least 20 mph Friday. Highs will hover in the low 60s in most areas.

Milder sunnier drier high pressure builds over Minnesota this upcoming weekend. It looks like we finally got the timing right for a spectacular weekend in Minnesota. Highs will reach the 70s both Saturday and Sunday in most of Minnesota.

Taste of summer next week

Our weather pattern looks even warmer next week. Highs in the 80s are likely most of next week.

We’ve earned it.

Enjoy!