Midwest Weekly Highlights - May 11-17, 2013

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Little Precipitation

The Midwest was relatively dry in the second week of May. Many stations recorded no precipitation for the week (Figure 1). Those stations that did report rain, typically had below normal totals (Figure 2). Some scattered stations reported totals of 2" or 3" but overall the dryer than normal conditions were far more widespread. Farmers took advantage of the favorable field conditions to make a lot of progress catching up on delayed planting.
 

Average Temperatures Mask Wild Daily Swings

On average, temperatures were pretty close to normal for the second week of May. In comparison to the first ten days of the month, the departures from normal were smaller and the spatial pattern was switched with warmer than normal temperatures in the west and cooler temperatures in the east. Average temperatures ranged from 5°F below normal in Michigan to 3°F above normal along the western borders of Iowa and Minnesota (Figure 3). With the dryer air mass in place, daily temperatures ranged from above normal maximum temperatures for much of the Midwest to below normal minimum temperatures across the region (Figure 4). Daily temperature records were mostly record lows in the first couple days of the week followed by record highs mid-week. The transition from freezing weather on the morning of the 12th to record warm weather on the afternoon of the 14th was sudden and impressively large (Figure 5). Stations in Iowa and Minnesota swung from freezing conditions to triple digit heat (Figure 6). Dozens of stations topped 100°F, many setting records for the earliest such day on record.
 

Lake Ice Surges On Shore

On the 11th, strong winds blowing across Lake Mille Lac pushed ice on shore. The ice surge stretched along about ten miles of shoreline including a neighborhood where the surging ice broke windows and damaged homes. The ice piled up several feet thick in many locations. A similar event in Manitoba on the 10th also saw ice blown onshore with enough force to destroy homes. Minnesota lakes were ice covered long into the spring (Figure 7) with ice-out occurring weeks later than normal (Figure 8) coming just one year after ice-outs that were among the earliest on record (Figure 9).
 

Severe Weather

Along with the more seasonal weather, severe weather was reported in five states during the week (Figure 10). Minnesota, Iowa, and Wisconsin saw the most activity. Severe weather in 2013 had been suppressed by cool spring weather across the region. Reports in the second week of May were not widespread and were limited to three days. Severe thunderstorm winds damaged trees and power lines from northern Iowa to southern Wisconsin on the 14th. Tornadoes on the 17th in southern Minnesota were mixed in among hail reports of 1" to 2" hail in Iowa and Minnesota. There has not been a tornado reported in Iowa since May 24, 2012 setting a record for the longest string of days without a tornado in the state.
 

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The Iowa Climatology Bureau also contributed to this report.
The Minnesota State Climatology Office also contributed to this report.