Midwest Weekly Highlights - February 22-29, 2012

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Two Main Waves of Precipitation

During the last week of February, precipitation totals ranged from 0.1 inches in parts of central Missouri and northwest Minnesota to 2 inches in southern Minnesota. The band of highest precipitation stretched from west to east from southern Minnesota and Iowa over to Michigan and northern Ohio. Precipitation totals within this band were at least 0.75 inches (Figure 1). The precipitation during the week mainly came in two waves; the first wave of precipitation occurred on February 23rd and 24th (Figure 2) and the second wave came through on the 28th and 29th (Figure 3). During the week, there were just over 850 daily precipitation records set (786 reported on the 29th) and 45 monthly precipitation records set (42 reported on the 29th).

When compared to normal, precipitation during the week was above normal in the upper Midwest and below normal in the lower Midwest. The highest departures of 1 to 1.75 inches above normal precipitation were found in southern Minnesota and northwest Iowa (Figure 4).


Unseasonably Warm Temperatures

Average temperatures were above normal across a majority of the Midwest (Figure 5). Western Minnesota and Iowa was the only region to experience near- to below-normal temperatures. Temperatures across the rest of the Midwest ranged from 1°F to 9°F above normal, with the highest departures of 8°F to 9°F in southern Missouri, northeast Wisconsin, and northeast Ohio. Maximum temperatures were also above normal across most of the region, with even greater departures of 9°F to 11°F above normal in the lower parts of the Midwest (Figure 6). The majority of the daily temperature records set during the week occurred in the later part of the week.


Central Midwest Snow Event (February 23 & 24)

The first major snow event of the week affected parts of Iowa, northern Illinois, southern Wisconsin, and Michigan, with some locations reporting 6 to 10 inches of snow (Figure 7). The system continued to move to the east on the 24th, bringing with it 3 to 12 inches of snowfall for parts of Michigan (Figure 8). Several daily snowfall records were set during this event and a couple of monthly snowfall records for February were set as well.


Upper Midwest Winter Storm and Lower Midwest Severe Weather Outbreak

A strong low-pressure system moved through the Midwest on February 28th and 29th (Figure 9), prompting winter storm and blizzard warnings for the upper Midwest and severe weather warnings for the lower Midwest.

The severe weather outbreak in the lower Midwest resulted in 20 tornado reports, 46 hail reports, and 112 high wind reports (Figure 10). The impact of the severe weather outbreak was especially felt in Harrisburg, Illinois (Saline County). In Harrisburg, a severe thunderstorm produced an EF-4 tornado early on the morning of the 29th, creating widespread damage and 6 fatalities in this town. Other fatalities as a result of this severe weather outbreak on Leap Day 2012 occurred in Missouri, Kansas, and Tennessee.

At the same time, the most significant winter storm of the 2011-2012 winter was occurring further to the north. Widespread snowfall of 6 to 10 inches, with locally higher amounts, affected much of northern Wisconsin and central Minnesota (Figure 11). There were 133 daily snowfall records and 8 monthly snowfall records for February broken during this event.

-MW-