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Accumulated Snowfall Average Temperature Departure Polar Vortex vs more typical configuration Ice Cave formations on the Apostle Islands

Midwest Overview - February 2014


Meteorological Winter Ends with Snowy Month

February brought above normal snowfall to a majority of the Midwest, with the greatest departure of 15" to 20" above normal in west central Illinois, southeastern Iowa, and northern Minnesota (Figure 1). Much of the region was at least 0" to 5" above normal, while there were portions of the region with below normal snowfall. Western Minnesota and portions of Upper Michigan were 0" to 10" below normal in terms of snowfall for February. Total snowfall ranged from only 0.1" in southern Kentucky to 30" to 40" in Upper Michigan and a small area of western Michigan along Lake Michigan (Figure 2). The major snowfall events during the month occurred on February 4th, February 12th-14th, and February 19th-20th.

Accumulated precipitation in February ranged from only 0.1" in western Minnesota to 5" to 6" in southern Kentucky (Figure 3). The significant totals in Kentucky mainly fell as rain, with much falling during the first and third week of February. Precipitation departures of 125% to 300% of normal spanned across the northern and central Midwest (Figure 4).

Unseasonably Cold February

Average temperature departures were significantly below normal for much of the Midwest during February, with below normal departures of at least 9°F spanning the upper Midwest (Figure 5). The greatest departures of -14°F to -16°F were in northeast Iowa, southeast Minnesota, and western Wisconsin. Average temperatures for February were 35°F or less for a majority of the region, with average temperatures of less than 0°F in northern Minnesota (Figure 6). There was some relief to the region during the third week of February, but the other weeks were unseasonably cool for the Midwest as a whole.

Record Breaking Winter of 2013/14

Snowfall
Much of the Midwest experienced the most severe winter in 30 years, with several blasts of arctic air and significant winter storms throughout winter. Highest seasonal snowfall totals were along Lake Michigan in western Michigan and in Upper Michigan, where season totals ranged between 80" and 175" of snow (Figure 7). The winter snowfall totals in western Michigan along the lake were 40" to 60" higher than normal in some areas, but the significant seasonal totals in Upper Michigan were near normal (within 20") (Figure 8). The remainder of the region also experienced above normal snowfall, with the exception of western Iowa, southern Kentucky, and a small portion of western Minnesota.

Temperature
Throughout the winter, the Midwest experienced several arctic blasts, some of which sent subfreezing temperature as far south as Florida. The arctic blasts resulted from a southward dip of the polar vortex. The polar vortex is a permanent fixture of the atmospheric circulation at the poles, but several times this winter, the polar vortex weakened which allowed fragments of cold air to surge into the middle latitudes (Figure 9). Average temperatures this winter ranged from 30°F to 35°F across the southern Midwest to -5°F to 0°F across northern Minnesota (Figure 10). In fact, the town of Embarrass in northern Minnesota (St. Louis County) had a mean winter temperature of only -5.5°F. Out of the 91 winter days in Embarrass, 32 recorded a minimum temperature of -30°F or colder, a Minnesota state record. There are actually seven days with minimums of -40°F or colder. For the rest of the region, winter temperatures in 2013/14 were below normal across the region, with the greatest departures of -9°F to -14°F below normal widespread across Wisconsin and Minnesota (Figure 11).

Great Lakes Ice Cover
As of March 6th, the total ice cover on the Great Lakes was 92.2%, making it the 2nd highest ice cover since 1973. The record ice cover of 94.7% occurred in 1979. In addition, for the first time since 1994, four of the Great Lakes (Superior, Michigan, Huron, and Erie) became 90% or more ice covered. Ice cover usually begins in mid-December, but this winter season it was reported by the end of November.


Impacts of Winter 2013/14

The cold and snowy winter of 2013/14 brought the familiar impacts of the late-1970s and 1980s back to the region, the last time many areas experienced a winter similar to the one this year. Early onset and extensive ice cover has made this winter the most challenging for the shipping industry in about 24 years, according to the president of the Canadian Shipowners' Association. This not only impacts the freight communities, but also the industries that use the cargo freighters are carrying. The cold temperatures produced sufficient ice on Lake Superior to allow over 85,000 visitors to trudge over the lake the explore the amazing ice cave formations on the Apostle Islands, giving this region an estimated economic boost of $10 million according to the Bayfield Chamber of Commerce and Visitor Bureau (Figure 12). This is the first time in 5 years the ice has been firm enough to allow passage. Other positive impacts of the ice cover on the Great Lakes include possibly helping to raise persistent low water levels on the upper Great Lakes and the formation of an ice bridge between Isle Royale in Michigan and the mainlands of U.S. and Canada, allowing for the passage of species, particularly wolves. In addition, the cold temperatures may benefit agriculture, as the freezing temperatures kill pests and slow the migration of invasive species.

With greater ice cover on lakes and rivers, ice shoves were more frequent this winter. Ice shoves result from strong winds pushing lake ice sheets into adjacent embayments and downstream. Ice shoves occurred from lakes Ontario and Erie in January and February, causing localized flooding in some areas (Figure 13). Flood-impacted areas included along the Niagara River, Rocky and Maumee rivers in Ohio, and North Sandy Pond in New York. The significant ice cover this winter increases the risk for break-up ice jamming in adjacent embayments and tributaries this spring, increasing the risk for flooding in these areas. However, the risk is reduced if the ice thaws gradually.

-MW-
Other contributors to this report include the Iowa Climatology Bureau, Missouri Climate Center, and the Great Lakes Environmental Research Laboratory.