Heavier western wildfire smoke blows in Wednesday; air quality may dip

Wildfire season is nearing peak intensity in the western United States.

Hundreds of wildfires are currently actively burning from California through the northern Rockies. The fires are belching out massive smoke plumes that are rising several thousand feet above ground level.

The mid-level wind flow between 5,000 and 15,000 feet is generally blowing from west to east across the northern U.S. That means the smoke plumes have a relatively straight path into the Upper Midwest this week.

The National Oceanic and Atmospheric Administration’s GeoColor satellite image at the top of this post shows widespread smoke plumes aloft in the Dakotas seeping into Minnesota.

The vertically integrated smoke forecast product from NOAA’s High-Resolution Rapid Refresh model shows thicker smoke plumes likely drifting over Minnesota overnight through Wednesday.

Smoke mostly aloft

Since most of the smoke is aloft, air quality readings at ground level are mostly good across Minnesota Tuesday.

But a cool front in northern Minnesota Wednesday could force some of that smoke down to ground level. The Minnesota Pollution Control Agency expects air quality to reach moderate (yellow) levels across much of northern Minnesota Wednesday.

Stronger southerly breezes Thursday should blow most of the low-level smoke northward, away from much of Minnesota.

Here’s the three-day air quality forecast for the greater Twin Cities area.

Here’s more detail on Minnesota’s air quality forecast from the Minnesota Pollution Control Agency.

Mon, Sept 12, 2022: An upper-level ridge has reestablished across the western US, and as a result upper level winds will bring more elevated smoke from ID/MT to the region early this week. Upper level smoke is visible across central and southern Minnesota today. However, this smoke is not expected to mix down to the ground. Today's weather will be very pleasant, and air quality should remain in the Green (good) category statewide today. A frontal boundary will push south from Canada tomorrow, and surface winds will be from the north across the northern half of the state. Smoke lingering from Canadian fires will be pulled to the ground on the northern side of this boundary. This smoke will move into northern Minnesota in the early morning hours. Air quality is expected to reach the Yellow (moderate) AQI category across the northern one-third of Minnesota tomorrow. Winds will gradually become southerly across most of the state Wednesday. This will cause the smoke to lift out of the state throughout the day. Northeast MN should return to Green AQI, but northwest MN may remain in the Yellow category Wednesday. A warm-up begins Wednesday and elevated ozone is possible in the SW corner of the state. By Thursday, all smoke should have cleared northern MN, but southern MN may see Yellow AQI due to ozone because of unseasonably warm temperatures.

Climate change expanding wildfire season

Wildfire season in the west still has plenty of time to run into this fall.

Climate change has extended both the seasonality and severity of wildfires in the western U.S., so the historical definition of wildfire season in the western U.S. has expanded in recent decades as western forests are subjected to a hotter and drier climate.

I expect more possible smoke episodes above Minnesota in the coming weeks. If meteorological conditions near the surface are right, some of that smoke could reach ground level where we breathe.

Stay tuned.