Wyoming Hits -26°F in Arctic Blast; 3 Feet of Snow in Michigan's Upper Peninsula

A bitter cold blast of Arctic air more typical of late December is plunging south over the Midwest, and will immerse most of the eastern two-thirds of the country in December-like cold for much of the coming week. Casper, Wyoming bottomed out Wednesday morning at a numbing -26°F, their coldest November temperature since weather records began in 1937. Casper's previous November record cold temperature was -21°F, set on Nov. 23, 1985. Laramie, Wyoming hit -22°F Wednesday morning, a record low for the date, and Yellowstone hit -20°F. The storm brought very strong winds with it, with several mountaintop locations recording wind gusts in excess of 80 mph earlier this week: 81 mph at Pikes Peak, Colorado, and 84 mph at Snowbasin, Utah. According to the Wednesday morning NOAA Storm Summary, a whopping three feet of snow (36.1") fell at Ishpeming in Michigan's Upper Peninsula over the past three days, and numerous locations in Michigan received more than 20" of snow, including Marquette (20") and Negaunee (32.5".) Snow amounts in North Central Minnesota were as high as 16.5", and northern Wisconsin got a peak of 26" at Gile. The storm and associated intense cold is being triggered by an usually extreme jet stream pattern, featuring a sharp ridge of high pressure over Alaska and a deep trough of low pressure diving to the south over the Central United States. This extreme jet stream pattern is due, in part, to the influence of Super Typhoon Nuri, which caused a ripple effect on the jet stream after the typhoon became one of the most powerful extratropical storms ever recorded in the waters to the west of Alaska last Saturday.


Figure 1. Departure of temperature from average at 2 meters (6.6') as diagnosed by the GFS model at 00 UTC November 12, 2014. A sharp kink in the jet stream (Figure 2) allowed cold air to spill southwards out of the Arctic over the Midwest U.S. Compensating warm air flowed northwards into the Arctic beneath a ridge of high pressure over Alaska. Data/image obtained using Climate Reanalyzer™ (http://cci-reanalyzer.org), Climate Change Institute, University of Maine, Orono, Maine.


Figure 2. Winds at a height where the pressure is 250 mb show the axis of the jet stream, seen here at 00 UTC November 12, 2014. A sharp trough of low pressure was present over the Midwest U.S., and an unusually strong ridge of high pressure was over Alaska. Data/image obtained using Climate Reanalyzer™ (http://cci-reanalyzer.org), Climate Change Institute, University of Maine, Orono, Maine.

Jeff Masters