Blue skies return: Upper wind trajectory blowing less smoke toward Minnesota

The mid and upper air flow has cleared most of the smoke from Minnesota skies.

Blue sky at the Weather Lab Friday afternoon
Blue sky at the Weather Lab in the southwest Twin Cities Friday afternoon
Paul Huttner/MPR News

Minnesota’s trademark blue September skies are back.

The mid and upper air trajectory has shifted more into the northwest. The change is enough to blow the thickest smoke plumes from the massive western wildfires southwest of Minnesota.

NOAA’s GOES-16 visible satellite loop shows thicker smoke smudges over the Dakotas and Nebraska Friday afternoon. Clearer skies and less smoke is visible over Minnesota.

NOAA GOES-16 visible loop Friday
NOAA GOES-16 visible loop Friday
NOAA/College of Dupage Weather Lab

Blue sky Saturday

The upper airflow should keep most of the smoke at bay again Saturday. A slightly thicker smoke layer may edge into southwest Minnesota Saturday.

NOAA HRRR model vertically integrated smoke product
NOAA HRRR model vertically integrated smoke product for 4 am Saturday
NOAA

In southwest Minnesota you may notice a white-tinted sky during the day, with a more vivid reddish sunset Saturday night.

Smoke layer scatters sunlight

Why is the sky white during the day and reddish at sunset when we see it through an elevated smoke layer?

707 smoky red sunset
Colorful sunset through a smoke layer at the Weather Lab in Victoria in 2015.
Paul Huttner/MPR News

It’s due to the light scattering properties of smoke particles. Smoke is very efficient at scattering out the blue light wavelengths. As a result, redder tones make it through to our eyes here at ground level.

How smoke and dust particles scatter sunlight
How smoke and dust particles scatter sunlight
NASA

Enjoy our lovely Minnesota blue skies.

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