Stormy Second Week of May

Stormy Second Week of May:

Since May 7th a number of low-pressure systems have brought a series of strong thunderstorms to various parts of Minnesota. These storms have produced large hail, strong gusty winds, heavy rainfalls, and tornadoes. In addition, the Twin Cities have reported mid-summerlike dew points with a record 67°F on May 9th, a record-tying 66°F reading on May 11, and a new record dew point of 70°F on May 12th.

Chronologically:

May 8th brought thunderstorms to many western portions of the state with Dawson (Lac Qui Parle County) reporting a record daily rainfall of 1.30 inches. May 9th the thunderstorms remained mostly in western Minnesota, but move north, where Rothsay (Wilkin County) reported a record rainfall of 2 inches. There were also over 80 reports of large hail (some with diameters of 3 inches) across western and central counties on May 9th, was well as wind gusts from 60 to 75 mph. There was also a report of a brief tornado near Gillman (Benton County) that day. By May 10th more thunderstorms were reported scattered across central Minnesota, with large hail reported in Le Sueur County. Kimball (Stearns County) reported a record daily rainfall of 1.20 inches that day.

May 11th was perhaps the most active day from the standpoint of the areal coverage of thunderstorms with 45 reports of large hail (up to 2.5 inches in diameter), numerous reports of strong winds (60-77 mph), and rainfall totals from 1 to 3 inches across a wide swath of the state.

Some isolated 4 and 5 inches of rainfall also were reported from other Minnesota volunteer observer networks. According to the NOAA-National Weather Service there were also 8 reports of either tornadoes or funnel clouds (still being assessed). Many long-term climate stations reported new daily record rainfall amounts for either May 11 or May 12. Some of these included:

2.83 inches at Marshall
2.69 inches at Willmar
2.67 inches at Mora
2.16 inches at Elk River

On Thursday, May 12th a frontal boundary across central and western Minnesota set up strong thunderstorms again, bringing 1.5 to 3.5 inches of rainfall to many areas, as well as widespread reports of large hail, and very strong winds (60-94 mph). Some areas around Sartell (Benton County) reported 3.5 inches of rainfall, and St Cloud reported a new record daily rainfall of 2.03 inches. Afternoon temperatures ranged from 96°F at Windom and Winnebago on the warm side of the front, to just 49°F at Grand Marais on the cool side of the front.

Not quite through the first half of May and many Cooperative Weather Observers are already reporting from 4 to 6 inches of rainfall for the month. Collegeville (Stearns County) has already measured 6.62 inches of rainfall this month, their 8th wettest May since 1892. The National Weather Service provided many ongoing reports about the storms this week.

Weekly Weather Potpourr:

There is a fascinating article published recently in the journal Weather and Climate Extremes that documents the intense mid-continent Cold Wave of February 2021. During this time many Minnesota communities recorded two weeks of subzero nighttime temperatures, while over 6000 new low temperature records were set throughout the central USA. This Cold Wave made national headlines for taxing the utility grid in Texas beyond its capacity and leaving many residents without heat. The article concludes that more states need to use their own climatological services to better assess risk management for such weather episodes.


According to the latest research from Chris Landsea of NOAA the evidence for a connection between climate change and Atlantic Hurricane activity is mixed. Certainly oceans are warming and providing more latent energy. Because of 50-80 variability in hurricane behavior, it is difficult to detect a significant effect of climate change. Perhaps more study and future trends will reveal significant and meaningful impact of climate change on tropical storms.


An article in this week’s AGU-EOS Bulletin highlights the linkage between air pollution and mental health. “In a recent study, researchers found that adolescents living in areas with relatively high levels of ozone experienced a significant uptick in depressive symptoms, such as sadness, loneliness, and feelings of self-hate.” Symptoms can come on suddenly when air pollution episodes are severe.

MPR listener question:

With all of the very heavy rains so far this month, my wife and I are wondering what is the largest single rainfall measurement for May in Minnesota?

Answer:

The greatest that I can find historically is 7.50 inches at Thief River Falls on May 29, 1949. That must have resulted in instant flash flooding.

Twin Cities Almanac for May 6th:

The average MSP high temperature for this date is 68 degrees F (plus or minus 11 degrees F standard deviation), while the average low is 49 degrees F (plus or minus 8 degrees F standard deviation).

MSP Local Records for May 13th:

MSP records for this date: highest daily maximum temperature of 92 degrees F in 2007; lowest daily maximum temperature of 44 degrees F in 1966; lowest daily minimum temperature of 29 degrees F in 1953; highest daily minimum temperature of 68 degrees F in 1900; record precipitation of 0.98 inches in 1962. A trace of snowfall fell on this date in 1935.

Average dew point for May 13th is 44°F; the maximum dew point on this date is 72°F in 1962; and the minimum dew point on this date is 10 degrees F in 1989.

All-time state records for May 13th:

The state record high temperature for this date is 95 degrees F at Beardsley (Big Stone County) in 1894 and also at Granite Falls (Yellow Medicine County) in 2007. The state record low temperature for this date is 10 degrees F at Tower (St Louis County) in 1997. The state record precipitation for this date is 4.63 inches at St Francis (Anoka County) in 1999. Record snowfall is 3.0 inches at Argyle (Roseau County) in 1924.

Past Weather Features:

May 13, 1997 brought a hard frost to much of the state with morning temperatures in the teens and twenties most places. It went down to 10°F at Tower and 15°F at Embarrass in northeastern Minnesota.

Minnesota farmers were frustrated during the planting season of 1999 by frequent rainfall. Over May 11-13 rainfalls were frequent and heavy delivering 3 to 5 inches of rainfall across many parts of southern and central counties. Many observers reported 6 to 8 inches of total rainfall that month.

Perhaps the warmest May 13th in state history was in 2007 when over 25 climate stations reported an afternoon temperature of 90°F or greater. Overnight temperatures remained in the 60s F in Cottonwood and Yellow Medicine Counties.

Outlook: 

Sunny and pleasant on Saturday, then increasing cloudiness and cooler on Sunday with a chance for widely scattered showers and thunderstorms. Dry and sunny on Monday, then a chance for widely scattered showers and thunderstorms Tuesday through Thursday, with temperatures running a few degrees cooler than normal. It should be a good week for Minnesota farmers to get some planting done.