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First frost northern / eastern ‘burbs

Deep down we knew there would be some nasty payback for 3 weeks of uninterrupted weather bliss, right? I had a hunch Mother Nature would make a scene, throwing tree branches, screaming at us for being so complacent — and sure enough, she reminded us who’s in charge on Sunday with gusts as high as 52 mph at MSP, a wild wind whipping up as high as 66 mph at Willmar. I’m still searching for my left contact lense — my sideburns were last observed over Waterloo, Iowa, moving south/southeast at a high rate of speed. I miss them.

A little perspective here: tropical storm force is (sustained) winds of 39, hurricane force is sustained at 74+ mph. mph. But the most recent storm fit the definition of a “gale”, defined as (non-tropical) sustained winds of 39-46You’ve heard Gordon Lightfoot’s classic “Gales of November”, forever immortalizing the sinking of the iron ore carrier, Edmund Fitzgerald, during an incredible storm on November 10, 1970. Winds on Lake Superior approached hurricane force with towering 30-35 foot seas; there are lot’s of theories about what ultimately sank the ship, killing all 29 aboard — a rogue wave may have literally snapped the 729 foot long vessel in half. My point? Large north-south contrasts in temperature can conjure up raging storms from late September into November — the transition from summer to winter isn’t smooth and linear; it can be exceedingly turbulent and severe. The bigger the temperature spread — the stronger the winds have to blow for the atmosphere to maintain equilibrium. That’s why the sharpest cold fronts whip up the strongest winds.

WRF/NMM Model — Predicted 7 am Wednesday morning temperatures. Note the extensive area of mid/upper 20s (darker blue shading) forecast for much of northern and eastern Minnesota and a huge swath of Wisconsin. The far northern and eastern suburbs of the Twin Cities, from Princeton and Isanti to Taylors Falls, Hugo and Stillwater, stand the best chance of a frost tomorrow morning. A breeze and increasing clouds may prevent a frost/freeze over roughly the western half of Minnesota tomorrow morning.

Today will be a big step in the right direction as winds ease up, the pressure gradient relaxing over Minnesota as a Great Lakes storm pushes east. Skies clear with more sunshine, and after a cool start the day should mellow into a fine example of late September at its best, complete with highs in the upper 50s to near 60. Not bad at all.

The rumors are true: many plants over northern and central Minnesota run the risk of freezing their buds off late tonight. Under clear skies with a dry atmosphere and just a light whiff of a breeze, temperatures will fall off rapidly, sinking into the 30s over much of the state. The “urban heat island” (more asphalt, concrete, businesses and homes re-radiating heat absorbed during the day) will keep the Twin Cities metro area a little warmer, most close-in suburbs bottoming out near 40 or so. If you have some plants you want to keep around awhile longer you might want to cover them up or bring them indoors, if possible. From St. Cloud, Elk River and Cambridge on north toward Aitkin and Grand Rapids the first widespread frost of the season is likely, a few towns farther north and east (over the MN Arrowhead) may experience a freeze, defined as 3-4 hours or more colder than 28 degrees F, cold enough to kill off almost all plantlife. As you can see from the data below showing the median date of the first 32/28/24 degree temperature, freezing temperatures in late September are not unusual at all.

City First 32 First 28 First 24

Brainerd 9/21 10/1 10/15

St. Cloud 9/24 10/5 10/17

Twin Cities 10/7 10/20 11/3

Latest USA Watches/Warnings. Freeze watches are posted for northeastern and north central Minnesota for Tuesday night/Wednesday morning, where the combination of clear skies, little or no wind and a dry, Canadian atmosphere may allow temperatures to fall below 28 F. for 3 hours or more, cold enough — long enough, to kill off most annuals. Click here for the latest national watches/warnings/advisories (click on the map to zoom in for even more information).

To see a National Weather Service graphic of the median date for first 32/28/24 for scores of Minnesota towns click here.

DNR Fall Foliage Update. A lingering drought coupled with an abnormally mild first three weeks of September has slowed down (and in some cases muted) fall color statewide. The most color now can be found near Willmar and Hutchinson, with another pocket of color in the Grand Rapids area. But color along the North Shore of Lake Superior is running 1-2 weeks later than usual, due primarily to an unusual string of 60s and 70s for much of this month. Click here to go direct to the DNR site.

Paul’s Outlook for the Twin Cities

Today: Cool sun much of the day, winds ease up — much nicer. Winds: N 5-15. High: ne0ar 6

Tonight: Clear, frost likely outside of town — best chance north/east of St. Cloud. Low: 36 (downtown) but frost possible far northern/eastern suburbs.

Tomorrow: Sun fading behind increasing high clouds, milder. High: 66

Thursday: Cloudy with showers developing, possible thunder. High: 62

Friday: Windy with periods of rain. High: near 60

Saturday: Lingering clouds, a shower or sprinkle. High: 58

Sunday: Partly sunny, brighter day of the weekend. High: 57

Monday: More sun, a bit milder. High: 62

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