Fresh to oppressive: Radical air mass changes ahead for Minnesota

Fresh Front

Minnesota is about to undergo an air mass transfusion. Make that two air mass transfusions.

We’ve been slogging through sticky dew points in the 60s this week. That changes as fresh breezes blow Wednesday. Dew points in the 40s will feel heavenly.

Dew point forecast for 5 pm Wednesday via NOAA.

Comfort Factor

It’s not the heat it’s the humidity, right? Actually, it’s the dew point. Dew point is an absolute measure of moisture in the air. A higher temperature number means we feel warmer. A higher dew point number means there’s more moisture in the air and we feel more sticky. Dew points in the 40s are extremely comfortable for most humans. Here’s a good guide to dew points and human comfort.

Dew point comfort range data via NOAA.

Tropical again late this week

We’re going to feel some radical swings in air mass comfort this week. First, we enjoy near-desert dry dew point in the 40s Wednesday. Then, a steamy tropical air mass with dew points into the 70s returns by this weekend. Talk about a change in air masses.

NOAA data via Iowa State University.

Steamy and stormy

Highs in the 90s look likely by this weekend. Ah, summer.

NOAA via Weather Bell.

Storm chances return 

There are still big model differences in timing and coverage of storms Thursday into Saturday. Why should this week be any different? I never take any individual model as gospel in summer. So think of NOAA’s GFS model below as a theme that hits the notion of occasional showers and thunderstorm waves Thursday into Saturday. There will be plenty of warm, steamy, dry, hours in between.

NOAA GFS model Wednesday to Saturday via tropical tidbits.

Forecasting precise timing and coverage of summer convective storms is like harnessing chaos theory. We’ll have to take individual storms waves as they come late this week.

Stay tuned.


  • Mary LaRue

    Paul, just want to say, <3 your blog! And, is there any chance you could in the next couple of days highlight the dew points, temperature, chance of rain forecast for Saturday in the Duluth/Two Harbors area in for the people running the marathon and praying for good weather?