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Posted at 12:43 PM ET, 03/16/2012

Back door cold fronts kick heat out of mid-Atlantic, Great Lakes

A remarkable 593 record highs were tied or broken from the East Coast to the Upper Midwest Thursday (compared to just 2 record lows) and record warmth is possible again in some of these same areas again today. But from the northern mid-Atlantic to the Great Lakes, temperatures are 10-25 degrees colder today than they were yesterday. In both regions, sneaky cold fronts have oozed south, placing a temporary halt on this historic March heat wave.

Back door cool fronts bring a temporary chill to the Great Lakes and northern mid-Atlantic (NOAA adapted by CWG)
These stealth fronts - known as backdoor cold fronts - often form in spring on the south side of high pressure systems positioned in the northern latitudes - especially over cool bodies of water which warm up more slowly than nearby land masses.

Presently, high pressure centers located 1) in the Atlantic off the coast of New England and 2) north of the Great Lakes, are steering cool air to the south and west (in a clockwise flow pattern), displacing the unseasonably warm air that had been in place.

Link: What is a back door cold front?

“Pneumonia front” rolls into downtown Chicago Thursday evening. Photo courtesy meteorologist Justin Berk on Facebook
In downtown Chicago, the cold front’s arrival was dramatic Thursday evening, especially near Lake Michigan where the cool waters enhanced the chill. Between 5 p.m. and 6 p.m. the temperature fell from 81 degrees to 55. Locals there dubbed it a “pneumonia” cold front. The Windy City had just experienced its first back-to-back to 80 degree days in March on record. Some spots along the lakefront dropped as low as 40.

The front triggered violent weather in parts of Michigan. In Detroit, the temperature Thursday surged to 77 - the second highest reading so early in the season on record. But as the cold front sank south, a severe thunderstorm spawned a tornado that damaged more than 100 homes in the town of Dexter, just west of Detroit.

Watch as frisbee golfers “play around” in the storm (they should’ve taken shelter but claim there “was no shelter to seek and nowhere to go” when the twister passed by):

Footage of the tornado in Dexter, Michigan on March 15, 2012. YouTube.

Such a strong tornado so early in the season is unusual in Michigan and possibly record-breaking, says Wunderground’s Jeff Masters:

...preliminary damage estimates from the National Weather Service put the twister at the boundary between EF-2 and EF-3 strength, with winds of 135 mph. If confirmed as an EF-3, this would be the earliest EF-3 or stronger tornado in Michigan history, going back to 1950, according to data from The Tornado History Project.

Position of back door cold front over northern mid-Atlantic Thursday at 5 p.m. Analysis above by meteorologist Dave Tolleris (WxRisk on Facebook)
The arrival of the back door cold front in Washington, D.C. area was neither as dramatic nor as violent as in the Great Lakes region. But temperatures fell markedly as the marine layer associated with the front moved in. After setting a record-breaking high of 82 degrees in the mid-afternoon, the mercury tumbled to 52 at 2 a.m., just twelve hours later.

In both the mid-Atlantic and the Great Lakes, the cool air from these fronts are forecast to erode. In the Great Lakes much above normal temperatures return quickly, with 70s this weekend. From Washington, D.C. to Philadelphia, temperatures will more slowly moderate - from 60-65 today well into the 70s by early next week.

Some other notable records statistics:

* Over the past seven days in the U.S, 1,803 record highs have been set compared to just 32 record lows.

* In 2012 in the U.S., 6,245 record highs have been set compared to just 533 record lows

* Rockford, Illinos had its earliest 80 degree reading on record Thursday

* Madison, WI - which hit 82 - had its warmest temperature so early in the year Thursday

By  |  12:43 PM ET, 03/16/2012

Categories:  U.S. Weather, Latest, Extreme Heat

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