Warm air above traps pollutants, triggers Minnesota air quality alert

An air quality alert is in effect for much of Minnesota, including the Twin Cities area, until noon Tuesday.

A layer of warm air above Minnesota is producing a temperature inversion. Light winds at the surface and the inversion layer are trapping pollutants near ground level.

The result is elevated particulate matter readings across much of Minnesota on Monday. Particulate matter readings around Minnesota have risen into the unhealthy range for sensitive groups at multiple locations including the Twin Cities and Duluth.

Weather balloons found warm air aloft on Monday — about 50 degrees around 4,000 to 5,000 feet above the Twin Cities.

That layer of warm air is trapping our air near ground levels with little mixing effect. Here’s more detail from the Minnesota Pollution Control Agency:

The Minnesota Pollution Control Agency (MPCA) has issued an air quality alert for central and northwestern Minnesota. The alert takes effect Monday, Jan. 9, beginning at 10 a.m. and runs until Tuesday, Jan. 10, at noon.

Light winds combining with moisture from melting snow will trap fine particulate pollution near the surface in central and northwestern Minnesota through noon Tuesday. Air quality will gradually improve Tuesday afternoon as winds increase which will improve dispersion and bring in clearer air from the west.

Fine particle levels are expected to reach the orange air quality index (AQI) category, a level considered unhealthy for sensitive groups, across northwestern and central Minnesota. This area includes The Twin Cities Metropolitan Area, St. Cloud, Moorhead, East Grand Forks, Alexandria, Brainerd, Hinckley and the tribal nations of Upper Sioux, Leech Lake, Red Lake, and Mille Lacs. Fine particle levels are expected to be in the orange AQI category, a level that is considered unhealthy for sensitive groups, for far southern and northeast Minnesota. In the orange area, sensitive groups should avoid prolonged time outdoors.

A weak weather system will bring some light ice to the Twin Cities Tuesday night, and snow to central and northern Minnesota through Wednesday.

Winds will improve mixing later Tuesday. Then, brisk northwest winds behind that system will pump in fresh Canadian air Thursday and improve air quality across Minnesota later this week.