Questions about the 2021 spring and summer forecast are abundant at this point in the winter, but those questions seem to have a little more energy than in the past few years. That may be due to the widely understood presence of La Nina in the Pacific Ocean and drought conditions in much of the western Midwest and the Plains.
But there's another angle behind the intensity of these forecast questions, and it's related to this coming crop season coming up on the tenth anniversary of massive flooding in the Western Corn Belt, specifically the Missouri River basin, in 2011. That season saw the Missouri in flood stage for practically the entire length of the river. Record snow water content in the 2010-11 winter, supplemented by spring snow and then record rain during May put a turbocharge into the flood mechanism.
There are a number of weeks left in the winter and then the entire spring season. But, at this point, the first component of flood threat -- winter snow water content in the upper Missouri Basin -- does not have even the average amount at this point in February. U.S. Army Corps of Engineers measurement of snow water content at the upper Missouri reservoirs at Fort Peck, Montana and Garrison, North Dakota show 10 and 8 inches, respectively, as of Feb. 7. Those amounts are under the averages for Feb. 7 of about 11 inches at Fort Peck and 10 inches at Garrison.
Back in 2011, the Fort Peck snow water amount was 13 inches and Garrison's content was 12 inches. When you look at those amounts and compare in percentages, the 2021 snow water content is 25% less at Fort Peck and 33% less at Garrison compared with 2011.
Another comparison to make is with the record amount of snow water for the date in another huge flood year, 1997. Both Fort Peck and Garrison had snowpack water content in early February 1997 of almost 18 inches. That total is far and away the highest snowpack water content volume in the U.S. Corps of Engineers records. (It needs to be noted that spring storms in 2011 led to the snowpack water content matching the 1997 volume.)
The upper Missouri basin does not look likely to add much to the snowpack water content in the next week, either. The upper Missouri's location is mostly under the core of cold Arctic high pressure, with the stormier boundary of the bitter cold air most prone to bring snow to the Central and Southern Plains. The spring outlook does offer above-normal precipitation, suggesting some flood risk. At this point, however, conditions show very little resemblance to the flood buildup of 10 years ago.
Bryce Anderson can be reached at email@example.com
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