Air quality alert continues through Thursday

It’s another day of air quality alerts for Minnesota. Our latest air quality alert is still in effect until 9 p.m. Thursday. Ground-level ozone is still elevated across Minnesota.

As of Wednesday afternoon, air quality readings across Minnesota are in the orange range (unhealthy for sensitive groups) across most of Minnesota. There are pockets of red (unhealthy for all) north of the Twin Cities across central Minnesota.

Here’s the wording on the current air quality alert:

The Minnesota Pollution Control Agency (MPCA) has issued an air quality alert for central and southern Minn., effective from noon on Tuesday, June 20, through 9 p.m. on Thursday, June 22. The affected area includes central and southern Minn., and the tribal nations of Leech Lake, Mille Lacs, Upper Sioux, and Prairie Island.

Ground-level ozone is expected to be high during the afternoon hours on Tuesday, Wednesday, and Thursday across central and southern Minn. Sunny skies, warm temperatures, and low humidity will create an environment favorable for two types of pollutants (Volatile Organic Compounds and Nitrogen Oxides) to react in the air to produce ground-level ozone. These pollutants will be transported by southerly winds from the Chicago area, northeast Iowa, and southeast Minn. Ozone will be highest during the afternoon and early evening hours when sunshine is most abundant, and temperatures are highest. Ozone will be low in the morning, late evening, and overnight.

Ozone levels are expected to reach the orange air quality index (AQI) category, a level considered unhealthy for sensitive groups, across central and southern Minn. The alert area includes the Twin Cities, Brainerd, Alexandria, Albert Lea, Marshall, Worthington, Rochester, Hinckley, St. Cloud, Ortonville, Mankato, and the tribal nations of Leech Lake, Mille Lacs, Upper Sioux, and Prairie Island. In the orange area, sensitive groups should limit prolonged outdoor exertion.

The forecast calls for slight improvements in air quality across Minnesota over the next few days.

Here’s the latest forecast discussion from meteorologists at the Minnesota Pollution Control Agency:

Updated Wed, Jun 21, 2023

As of mid-afternoon Wednesday, ozone is red (Unhealthy) in the north Twin Cities Metro northward to St Cloud, Princeton, and Milaca. Ozone in the rest of the Minnesota is orange (USG), except for yellow (moderate) over far northwest and northeast Minnesota. Particulate AQIs are yellow throughout Minnesota due to leftover wildfire smoke.

Southerly winds, mostly sunny skies, and warm temperatures will continue over the Midwest for Thursday. A cold front will approach our western border late Thursday with some scattered showers and thunderstorms in our northwest counties. Southeast flow will continue bringing pollution from the Chicago area into Minnesota, and there will also be some ozone precursors in the light wildfire smoke persisting over the area. An increase in low level moisture should create some partial cloud cover that will lead to slightly lower ozone compared to Tuesday and Wednesday. The relatively dry and mostly sunny conditions combined with a dirty air flow will cause ozone to rise well into the Orange category, which is Unhealthy for Sensitive Groups (USG) in much of the alert area.

On Friday the cold front will progress into North Central Minnesota. There will be more clouds and greater rain chances, but far eastern and southeast Minnesota should remain mostly sunny with lesser rain chances. Ozone has a decent chance of reaching Orange again Friday in east central and southeast Minnesota, including the Twin Cities metro. The front will stall over the area during the weekend and will be a focal point for scattered showers and thunderstorms. Greater cloud cover and rain changes should bring ozone AQIs down to Green (Good) and Yellow (Moderate). However, smoke from wildfires in Ontario may travel south and southeast over the North Shore and Lake Superior down to Duluth. Fine particulate AQIs may reach Orange in parts of northeast Minnesota over the weekend. Particulate AQIs in the rest of the state will be Green to Yellow.

So far, forecast models suggest wildfire smoke will remain at relatively low levels across Minnesota for the next few days.

Stay tuned.