Well, that was nice!
Our pleasantly dry air mass was enjoyable but brief. Southerly winds advect an increasingly tropical air mass over the next 48 hours. Dew points rise from the comfy 40s to the sticky 60s Thursday into Friday. The core of our inbound Guam-like air mass arrives Friday into Saturday as dew points hit 70 degrees in parts of the Upper Midwest.
Here’s a look at model generated dew point values for the next week via Iowa State University’s Meteogram Generator. I’m uncomfortable just looking at this graphic.
All the ingredients come together for some 90-degree heat for southern Minnesota including the Twin Cities. The good news? Relief arrives next week. Here are the NOAA forecast numbers for the Twin Cities. Northern Minnesota shaves 10 to 15 degrees off these numbers.
All that heat and humidity is fuel for thunderstorms that have the potential to dump some heavy rainfall totals. There is still huge model spread regarding timing and coverage on storms the next few days. But the potential for locally heavy rain is there. NOAA’s GFS model paints some 2″ to 4″+ totals across most of central and northern Minnesota by Monday. Again, this is not gospel but a guide to rainfall potential this weekend.
Grandma’s Marathon: Cool and wet?
The forecast maps favor cool and potentially rainy conditions for this year’s Grandma’s Marathon between Two Harbors and Duluth. The Canadian model typifies the chance for rain and thunder Saturday up north.
The Twin Cities rides the hot, steamy, southern edge of storms Saturday. Highs Saturday will be in the 90s south and 70s along Lake Superior.
We’ll have to deal with more precise timing on thunderstorms in the shorter term this weekend.