Breathing Easier: Metro AQI improves; Pine tree effect adds +10F up north

Fresh Canadian Breezes

We can thank Canada for our fresher breezes today.

After the Twin Cities Air Quality Index (AQI) spiked Tuesday, a fresh north breeze has cleaned out the “gunk” over much of Minnesota today.

Temps ran +10 to +20 degrees warmer Tuesday in the forests of northern Minnesota. Today’s Updraft explains why the “Pine Tree Effect” reaches peak from now into early March.

We’ll also tally up some impressive snowfall totals for our neighbors down I-94 in Madison, Milwaukee & Chicago.

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11.7″ snowfall in Beach Park, IL (near Waukegan in the north suburbs)

10.1″ snowfall total in Richmond, IL (far NW Chicago suburbs near WI state line)

14.5″ in Sheboygan, WI (north of Milwaukee)

36F high at MSP Tuesday

45F high at Crane Lake in far northern Minnesota Tuesday

60s in Rapid City, SD this weekend?

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Breathing Easier: Metro AQI improves overnight

My dad always said our chilly winter breezes “keeps out the riff-raff” in Minnesota.

Our latest cool push did a number on a stagnant, polluted air mass overnight.

A north breeze from a cleaner source region” that we call Canada brought in fresh air and mixed out particulate matter and pushed it south.

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Image: College of DuPage

Check out the drop in AQI values for the Twin Cities in the past 24 hours…from 109 to 57 and falling.

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“Pine Tree Effect” season in full swing:

With roughly the same air mass in place Tuesday, it was +6F to +9F warmer up north than in the metro…and as much as +20F warmer than in Fargo Tuesday.


There were some slight differences in could cover…but the bigest factor was the “pine tree effect.”


Image: NASA MODIS Terra via UW Madison

Pine trees are remarkably efficient at absorbing and reradiating our stronger late winter sunshine and warming the air near the ground. Areas with fewer trees and deep snow cover act like a mirror, and reflect incoming (short wave) solar radiation right back into space before it can “convert” to “long wave” radiation which is good at heating the air around us.


The pine tree effect peaks this time of year…as a higher sun angle and intensity combines with widespread snow cover to produce the dramatic differences on sunny days with light winds

Close Call: Winter storm pounds Milwaukee & Chicago

I spent 4 years counting up inches in Chicago during my career.

There was plenty to count with the latest “productive” winter storm that raced through the Midwest.

A trace of snow came as close as Rochester and La Crosse…but heavy totals fell around Madison, Milwaukee & Chicago.

After one of the least snowy winters on record, the tide turned in February in Chi-Town.

Some details from the Chicago NWS.

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Forecast: Cooler weekend breezes – signs of a thaw late next week?

You’ll feel the cooler breezes the next few days as Canadian air sags south.

Monday’s clipper looks to target southwest Minnesota…and may produce a few inches of snow for Luverne & Pipestone.

There are signs of a thaw late next week, as Pacific air mass tries to push in from the west. Upper 30s look quite possible again…and I wouldn’t be shocked to see a few 40F+ readings popping up west of the metro by next Friday & Saturday.

With deep snow cover to the south, it looks like our spring warm-up this year may be driven by some “Chinook modified” breezes from the west.

Rapid City may touch 60 degrees Saturday, as downslope winds blow in a milder air mass from the northern Rockies.

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I don’t see any real “Wurzer Weather” (warm) anytime soon…but hang in there. With no significant snowfall in the forecast and a much higher March sun angle we may have the ability to pop 40F in the next week or so.

Stay tuned.


  • Gordon near Two Harbors

    I would change the term “Pine Tree Effect” to “Evergreen Effect”, because balsam fir and spruce trees are the evergreens that far outnumber pines across most of the northern landscape, and likely drive daytime warming more than pines do.