The month of May is certainly not known for major snow events, but they do occur from time to time over the Plains region of the U.S. Back on May 1-3 of 2013, a storm dropped over a foot of snow over parts of southeast Minnesota and western Wisconsin. This broke many May snowfall records across the region, with Blooming Prairie (a town in southeast MN) getting a whopping 18 inches. Just this year, a May snowstorm occurred over parts of Nebraska and into portions of Minnesota on May 1st. As much as 10 inches accumulated near the town of Atkinson (a town in northeast NE) with this storm. The common ground that most of these historic May snow events share is that they hit early in the month. One of the latest May snowstorms on record, occurred back in 1947. This historic system broke the mold, as it struck on the last days of May, during a time when folks typically rest easy in knowing that there will be no further snow events until the coming fall. Just as folks were finishing up their Memorial Day celebrations and winding down at the end of a long weekend, an epic snow event began across the Plains, that lasted from May 27th to the 29th. As unusual and memorable as this event would have been to live through, it is sometimes referred to as the "nearly forgotten snowstorm." Perhaps this is because folks wanted to forget it as soon as the snow melted. Either way, the event made for a memorable Memorial Day holiday, not because of great outdoor grilling and picnics, but because of bitter cold temperatures and the several inches of heavy, wet snow that piled up.
By mid-to-late May, the angle of the sun becomes as high as it is in late July. In late May, the sun shines for around 15 hours a day, and night only lasts about 9 hours. The longest day of the year (the summer solstice) is only a few weeks away once you hit late May. These factors make it very difficult for the chilled air masses in Canada to have much bite as they progress southward into the Plains of the U.S. Even with the odds stacked against this from happening, old man winter mustered up the perfect storm to make this transpire in late May of 1947. On the morning of May 27th, a strong arctic high pressure system was stationed over northwest Canada. This region was still snow covered, and the air mass became increasingly chilly, as the high remained in place. At the same time, a low pressure system was strengthening over central Nevada. The deepening low helped induce a major buckle in the polar jet stream winds blowing over Canada. This southward shift of the jet stream in western Canada meant that the unseasonably cold air mass in northwest Canada would now come crashing southward into the northern Plains.
As the Nevada low headed east across Colorado and western Kansas on the evening of the 27th, the cold air began to feed into the northern side of the system, changing a rain/snow mix to all snow over much of Wyoming and into Western Nebraska. By the morning of the 28th, record cold temperatures for late May were experienced over North Dakota and into Montana. Bismarck hit its coldest recorded temperature in late May, as the thermometer plummeted to a reading of 23F. Other parts of northern North Dakota saw temperatures fall into the teens. As this cold air headed southeast, other record cold temperatures were experienced into South Dakota and Minnesota. The late freeze spelled out partial to total losses for fruit producers in the northern Plains. As the precipitation band continued to trek eastward over northern Nebraska and northern Iowa on the 28th, heavy, wet snow continued to pile up. By the night of the 28th and early into the 29th, southwest and central Wisconsin saw the brunt of the accumulating snow. When all was said and done, an impressive swath of 6-10 inches fell from Wyoming east into Wisconsin. The heaviest totals occurred in the panhandle of Nebraska, as folks in Harrison and Alliance measured a foot. Impressive totals occurred all the way east into southwest Wisconsin, where Viroqua measured a total of 9 inches by the 29th. The snow that piled up had a very high water content, and the extremely heavy character of the snow damaged the fully-leafed-out trees in the area. This resulted in many power outages over the region. Once the sun came out the next day, much of the snow melted away, but the cleanup of major tree damage and the mending of snapped powerlines likely lasted for several days to follow.
The late 1940's were characterized by a rather brutal run of winters across the Plains, so it must have been a tough pill to swallow when this late spring snowfall occurred across region. The agricultural producers over the region had to somehow make it through the killing frosts and heavy snows that struck. Thankfully, no other late May storm has come close to matching the fury and extent with which this one struck. Shortly after the snow melted, a series of low pressure systems produced heavy rains over the area, resulting in historic flooding over portions of Iowa and Nebraska, during the following month of June. It must have seemed that the odds were really stacked up against folks trying to earn a living in the agriculture industry that year. 70 years have now passed since the fateful Memorial Day of 1947, but the images are likely still vivid for those who lived through that bizarre late-May snow event.
Photo Courtesy: http://westbyhistory.blogspot.com/2014_05_01_archive.html
Photo was taken near Westby, Wisconsin on May 29th, after the historic late May snow event had ended.