January 18-24, 2011
Midwest Weekly Highlights - January 18-24, 2011
The Status Quo
The weather across the Midwest changed little from the week prior, other than it was decidedly colder. Occasional snow a fell in the region, and central portions of the Midwest received the largest amounts from a storm early in the week.
Temperatures were well below normal across the entire Midwest this week, with the largest departures in the west central potions of the region. Average daily temperatures ranged from 7°F to 8°F below normal along and north of the Ohio River to 16°F to 18°F below normal in southwestern Minnesota and northwestern Iowa (Figure 1). Conditions in southeastern Kentucky were not quite as extreme, with temperatures ranging from 3°F to 4°F below normal.
Lots of Snow, Not Lots of Water
Snowfall this week was 200 to 700 percent of normal across the southern half of the region, and normal to above normal around the Great Lakes (Figure 2). There was a marked lack of snow across the southern two-thirds of Minnesota, northern Wisconsin and northern Iowa. The persistent northwesterly flow produced plenty of lake-effect snow across the Michigan Upper Peninsula and in western lower Michigan (Figure 3). Despite the abundant snowfall, precipitation for the week was well below normal except for across northern Missouri and southwestern Iowa (Figure 4), a pattern closely resembling the overall precipitation pattern for the month so far. There was little change to the January 18 U.S. Drought Monitor (Figure 5), although dryness has been expanded north into central Missouri and southern Illinois. However, this depiction does not reflect the precipitation that fell in the region during this week.
Heavy Snow Blankets Missouri
The first significant storm this week occurred on January 19-20. An upper level disturbance reflected on the surface as a weak low brought heavy snow to the central Midwest (Figure 6). In anticipation of the snow winter weather advisories and warnings were in effect for an area stretching from the Colorado-Kansas border eastward through Ohio on January 19th (Figure 7). This storm produced a wide band of 6 to 12" of snow across central Missouri into western Illinois, generally in the Interstate 70 corridor (Figure 8). Lighter amounts occurred further north and south of this band. Low winds with this event kept blowing and drifting of the snow to a minimum, but there were travel delays and numerous reports of accidents. More than 1,000 schools closed across Missouri and western Illinois on January 20th as a result of the snow.
More snow came on the heels of this storm as another low pressure system exited the Central Plains (Figure 9). This system began spreading snow across southwestern Iowa and northeastern Missouri on January 22nd. It took a more southerly track than the storm two days earlier, and the heaviest snow was confined to northeastern Missouri and southern Iowa (Figure 10). Four to eight inches of snow fell in these areas, while amounts diminished further east and south.
Brutal Cold in Upper Midwest
Arctic high pressure dropped out of Canada and into the Midwest in the wake of the snowstorm on January 20th. On the morning of January 21st the axis of the high extended from Hudson Bay, Canada south to the Gulf Coast. Clear skies, calm air, and a snow cover of from one to two feet or more across Minnesota and the northwestern half of Wisconsin resulted in widespread low temperatures from -20°F to less than -40°F across those areas (Figure 11). In Minnesota, low temperatures plummeted to -46°F at International Falls (Koochiching County) and Babbitt (St. Louis County). Six other locations in St. Louis, Koochiching, and Itasca Counties reached lows from -40°F to -43°F. In Wisconsin numerous locations were -30°F or colder, with -36°F recorded at Barnes (Bayfield County). Maximum temperatures across most of the northern half of Minnesota did not reach 0°F on January 21st (Figure 12). A number of record minimum and record low maximum temperatures were set the last four days of the period in the upper Midwest.
Quiet End
The week ended with slightly warmer air spreading through the southern half of the region ahead of yet another weak low pressure system. This low did produce some light snow across the central portions of the region. Freezing drizzle occurred in portions of Illinois and Indiana making travel difficult during the morning hours of January 24th. At the end of this week an inch or more of snow was on the ground except for far southern Missouri and the southern half of Kentucky (Figure 13).
-SDH-