Severe winter weather developed across Michigan during much of the second half of January with the passage of several Arctic-origin air masses and a major winter storm through the Great Lakes region. The frigid air masses were associated with the shift of a large portion of the polar vortex circulation (normally located across high latitude, arctic areas) into mid-latitude areas of eastern North America during the second week of the month.
During the last week of the month, the pattern resulted in extremely cold temperatures, strong winds, and a prolonged period of heavy lake effect snowfall. The adverse weather resulted in widespread closed schools, businesses, and major travel disruptions across the state and region.
Not surprisingly, mean temperatures for January were below-normal statewide, with means generally ranging from near 2 degrees below normal across far southern sections of the state to more than 4 degrees below normal in the north.
Extreme minimum temperatures for the month occurred in two episodes on the 20th and 22nd and 29th and 31st and ranged from just below zero temperatures in lakeshore areas immediately downwind of Lake Michigan to minus 10 degrees to minus degrees over most sections of the state to less than minus 30 degrees in some interior sections of Upper Michigan (low wind chill temperatures were generally in the minus 20- to minus 40-degrees range).
The temperatures in some areas were cold enough to injure sensitive overwintering perennial crops (especially given the prolonged milder-than-normal weather that preceded the cold outbreak), but the extent of any damage is unknown at this point.
It is important to note that mean temperatures for the month would have been significantly colder if not somewhat averaged out by much above normal temperatures during the first week of the month (the end of a period of abnormal warmth that began in early December).
Similarly, extreme low minimum temperatures could also have been significantly colder in many locations had it not been for the moderating influence of open water on Lakes Superior and Michigan (minimum temperatures just upwind of the lakes in Minnesota, Wisconsin, and Illinois were generally 10 to 15 degrees colder than those in Michigan).
January precipitation totals were near to above normal in most locations, ranging from less than 1.5 inches across extreme southeastern and northwestern sections of the state to more than 4 inches (more than 150 percent of normal) across lake effect snow belt areas of the western Lower and northern Upper Peninsulas.
Short-, longer-term outlook
At the beginning of February, the upper air troughing pattern which brought so much cold weather to the region in January moved northeastward into the northern Atlantic and was replaced by an upper ridge which resulted in a dramatic warm up in temperatures and a significant thaw.
Most recent medium-range forecast guidance suggests an eventual transition to a broad troughing feature across much of the lower 48 states which would lead to a return of normal- to below-normal mean temperatures (although likely not nearly as extreme as those of late January) and to an active storm track through the Midwest which would favor above-normal precipitation totals, at least some of which will be snowfall.
Given this recent guidance, most long-lead outlooks have been adjusted toward cooler temperatures (earlier outlooks for the late winter and early spring had suggested milder-than-normal mean temperatures).
The updated NOAA Climate Prediction Center outlook for February now calls for normal- to below-normal mean temperatures and above-normal precipitation totals. The latest 3-month outlook for February through April calls for the equal odds scenario of below-, near-, and above normal mean temperatures statewide with near equal odds below-, near-, and above-normal precipitation totals across the northern two-thirds of the state, with below-normal totals expected across the southern third.