'Very unhealthy': Thick smoke; air quality alert includes Twin Cities until 6 a.m. Thursday

Air quality sensors indicate 301 ppm particulate reading in Brainerd.

The sun is obscured by thick smoke.
The sun is obscured by thick smoke Tuesday, July 20, 2021, in Duluth, Minn. Winds from the north are pushing smoke down from Canadian wildfires.
Dan Kraker | MPR News

Canadian wildfire smoke is getting thicker across much of northern Minnesota Tuesday.

Air quality has reached “very unhealthy” levels in Brainerd and much of north-central Minnesota Tuesday afternoon according to monitors from the Minnesota Pollution Control Agency. I’m not sure if it’s a record but I have never seen a particulate reading as high as the 301 ppm observed in Brainerd today on the map above.

A weak cool front sliding south is bringing cooler temperatures to northern Minnesota. It’s also pushing wildfire smoke from dozens of Canadian wildfires further south into Minnesota. The latest air quality alert includes the Twin Cities until 6 a.m. Thursday.

Air quality alert until 9 am Thursday
Air quality alert
Minnesota Pollution Control Agency

The Minnesota Pollution Control Agency (MPCA) has issued an air quality alert for northern, central, and southeast Minnesota, effective Tuesday, July 20 through Thursday, July 22, at 6 a.m. The affected area includes Hibbing, International Falls, Bemidji, Roseau, East Grand Forks, Moorhead, Brainerd, St. Cloud, the Twin Cities, Rochester, Mankato, and the tribal areas of Leech Lake, Red Lake, Fond du Lac, Mille Lacs, Upper Sioux, and Prairie Island.

Heavy smoke from wildfires located north of the Canadian border in Ontario and Manitoba was transported into northern Minnesota overnight by northerly winds. Today, fine particle levels are expected to remain in the Purple AQI category, a level considered very unhealthy for everyone, across north central Minnesota. Heavy smoke will remain in this area through Wednesday. Tomorrow, fine particle levels are expected to be in the Red AQI category, a level considered unhealthy for everyone, across northern Minnesota.

Smoke is expected to mix down to the ground over northern Wisconsin and move into central and southeast Minnesota this afternoon. Fine particle levels are expected to reach the Orange AQI category, a level that is considered unhealthy for sensitive groups, today across central and southeast Minnesota and remain in the Orange AQI category tomorrow. Fine particle levels will begin to improve across the state beginning Wednesday evening as winds will begin to move the smoke out of the state. By Thursday morning, air quality should be improved below alert levels statewide.

The National Oceanic and Atmospheric Administration’s HRRR model vertically integrated smoke product forecast continues to show thick plumes of smoke drifting southeast across Minnesota and the Upper Midwest through tonight into Wednesday.

NOAA HRRR model vertically integrated smoke product
NOAA HRRR model vertically integrated smoke product forecast Tuesday evening.

The entire state of Wisconsin is also under an air quality alert for smoke.

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