March 15-21, 2005
Midwest Weekly Highlights - March 15-21, 2005
Calendar Winter Ends With One More Snowstorm
The spring equinox occurred during the morning of March 20, making March 15-21 the last week of calendar winter. The week was generally very dry in the Midwest, with only a small swath of Minnesota and Wisconsin receiving more the one inch of precipitation (Figure 1). Most of the southern Midwest was exceedingly dry, with the southwestern quadrant receiving less than 25% of normal precipitation (Figure 2). However, the precipitation that did fall in the Midwest largely fell as a great snow storm in southern Minnesota, central and northern Wisconsin, and northern Michigan (Figure 3). Many locations reported a foot or more of snowfall in southeastern Minnesota and southwestern Wisconsin between March 18-20. The precipitation in the warm sector of the storm was much lighter, with very dry air evaporating most of the rain before it hit the ground across the central Midwest. The warm sector of this system did leave a signature on the weekly temperature departure map, with the least below normal averages being found just south of the storm track (Figure 4). North of this band, temperatures remained 6 to 8°F below normal, thus insuring that the overrunning moisture from the south would fall as snow. Conditions were abnormally dry in the south-central Midwest by the end of the period, but a strong system from the southwestern U.S. started raining in the dry zone prior to the end of the day on the 21st.
Large Snowstorm Paralyzes Portions of Minnesota and Wisconsin
A strong low pressure center crossed the Rocky Mountains and started to approach Iowa on the evening of March 17 (Figure 5, College of DuPage). A trough of low pressure extended eastward ahead of the low center along a stalled frontal boundary near the Iowa border with Minnesota, ensuring that cold air stayed to the north. Winter storm warnings were issued for much of Minnesota and Wisconsin by the next morning (Figure 6, Storm Prediction Center), as a great band of snow producing clouds extended across the states from the low center near Sioux City, IA (Figure 7, University Corporation for Atmospheric Research - UCAR). The snow was quite heavy at times (Figure 8, UCAR), falling at more than an inch an hour in southeastern Minnesota and southwestern Wisconsin. A swath of 20 inch snowfall totals resulted in this area due to the combination of intensity and duration of the main snow event (Figure 9, National Weather Service - NWS). Snowfall totals at observer station locations can be seen on maps from the NWS field offices at Chanhassen, MN (Figure 10a, NWS), and La Crosse, WI (Figure 10b, NWS).
The most heavily impacted large community in the storm path was Rochester, MN, which set its all-time, 1-day snow fall record with 16.9 inches on March 18, and received 20.2 inches in all from the storm. The snow was so plentiful that even the precipitation record for the day fell (1.49 inches of water equivalent). Regional transportation was crippled by the storm. Most of I-90 was shut down in southern Minnesota, and some 277 vehicles were reported off the road by the State Highway Patrol in Minnesota. Minneapolis, MN, while missing the brunt of the storm, still set a snowfall record of 4.6 inches on March 18 and a total of 5.3 inches. Nearly 300 crashes with property damage and 46 injuries were recorded in the state, with 214 occurring in the Minneapolis - St. Paul metro area. More than 260 flights were cancelled out of the Minneapolis - St. Paul Airport, and some municipal airports were closed. Daily snowfall records were also set on the 18th at Mason City, IA (11.8 inches) and La Crosse, WI (13.9 inches). A Minnesota state record for March 18 was set in the small southern border community of Kiester, which recorded 21 inches in a 24-hour period. Areas to the south of the storms received light rain showers in general, although some thunderstorms were embedded at times, and a small F0 tornado caused damage to a few structures near Taylorville, KY, on the 19th.
After the slow passage of the storm, a brief reprieve brought sun to the region on the 21st. However, just as the day was ending, heavy rain bands from a large low pressure system approaching from the southwestern U.S. reached western (Figure 11a, NWS) and southern (Figure 11b, NWS) Missouri. The precipitation that fell during the evening of the 21st was recorded at most stations on the morning of the 22nd, so this storm will be described in more detail in the next Climate Watch segment.