AC to heat in 36 hours? Patchy frost north; “Ring of Fire” weekend?

93 Sunday PM in the metro

40s blankets for sleeping, furnaces kicking in by Tuesday morning?

86 degrees in Ely at 4:33pm Sunday

39 degrees in Ely and patchy frost by 6am Tuesday

47 degrees – temps plunge nearly 50 degrees in just over 36 hours?

Dry spell ends – Sunday night rains end a 12 day dry spell in most of Minnesota

Free AC:

Talk about a change of air masses!

I often blather on about how Minnesota sits in the middle of the North American continent (there’s some scintillating party conversation) as air masses freely sweep through the Upper Midwest.

There are no mountains nearby to obstruct or protect us from tropical air masses from the Gulf of Mexico or chilly dry Canadian winds from the north.

49 comet air mass.jpg

Source: NOAA

The result? Hot windy weekends punctuated by raucous thunderstorms out breaks as the two air masses collide and battle for supremacy over Minnesota.

The Canadian air has won the latest round, at least until Wednesday. Later this week, a warmer more humid air mass will gradually ooze north again. That means warmer days, and a return to scattered thunderstorms.

Enjoy the free AC for now, and manage the windows accordingly to avoid waking up with a chill early Tuesday morning!

From AC to Frost up north?

86 in Ely Sunday must have felt great for early season BWCA trippers with thousands of still chilly lakes & sparkling bays to jump into and cool off. Hopefully they brought the good sleeping bags along too.

Temps will dip into the upper 30s from Grand Forks to Ely Tuesday morning. With low dew points, light winds and clear skies, scattered frost is quite possible.

49 lows.png

Source: NWS

So is it unusual to get frost this late in the year up north? Not really. A good look at the map below shows frost is possible late into June in the colder nooks and crannies “up north.”

49 frost dates.PNG

Source: MN Climate Working Group

“Ring of Fire” this weekend?

I talked about the “Bermuda High” and what it means for Minnesota in this morning’s Updraft post.

One feature that often rides the western edge of the Bermuda High in summer is the meteorologically infamous “Ring of Fire.”

49 ring 2.PNG

Source: stormcentral1st.com

The Ring of Fire is a weather pattern that favors heavy T-Storms that fire along the periphery of the Bermuda High. As cooler air bumps into the hot, humid dome of high pressure, storms tend to blow up and ride along the edge of the Bermuda High. These so called “ridge runners” can be severe, and often pack high winds and hail.

Long lived wind storms called “derecheos” can also sweep along the ring of fire. Several famous “blow down” events are the result of derecheos that sweep around the ring of fire.

The infamous “BWCA Blowdown” of July 4th 1999 was a derecheo that raced around the ring of fire for more than 48 hours.

49 1999jul4-5rpts.jpg

Source: NOAA/SPC

The BWCA monster derecheo travelled 6,000 miles! That may be the longest recorded path length for a derecheo.

Meteorologically speaking, derecheos are defined by three things.

-A path length of at least 250 miles.

-At least 3 reports of hurricane force (74 mph) winds separated by at least 40 miles.

-No more than 3 hours between damaging wind events.

There have been other accounts of so called “trans-continental derecheos” in the past. Some have travelled over 1,000 miles.

As high pressure builds in this weekend over the eastern and central USA, Minnesota looks to be on the western edge. That could put us in the infamous and stormy “Ring of Fire.”

Stay tuned!

PH

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