HydroClim Minnesota for Early March 2021

A monthly electronic newsletter summarizing Minnesota's climate conditions and the resulting impact on water resources. Distributed on the first Thursday of the month.

State Climatology Office - DNR Division of Ecological and Water Resources, St. Paul
Distributed: March 9, 2021

What happened in February 2021:

  • February is on average the driest month of the year. Normal precipitation is generally less than an inch for most locations. For February 2021, most places in the state fell short of normal. The few exceptions were some pockets of higher moisture in the south and east central. One of the higher monthly precipitation totals found was .71 inches at Lamberton. The lack of precipitation caused the spring flood threat to remain quite low this season. The preliminary average precipitation total for the state was .41 inches or .27 inches below normal. February 2021 was the sixth month in a row with below normal precipitation. The preliminary six month statewide deficit since September 2020 is 3.04 inches.
    [see: February 2021 Precipitation Total Map  | February 2021 Precipitation Departure Map  | February 2021 Climate Summary Table  |  February 2021 Percent of Normal Precipitation Map ]
  • There was one notable snow event for an otherwise quiet month.
  • Snow associated with a passing low-pressure system, spread from southwestern into central Minnesota during the morning of Sunday February 28th. A band of very heavy snow, lasting 2-3 hours, formed from Canby towards Willmar, and the southern St. Cloud area. Light snows made it as far south and east as Mankato and the Twin Cities, and as far north as Duluth, Two Harbors, and Grand Marais. Accumulations of 7 to 8.5 inches were reported by volunteer observers and the public near Kimball and South Haven, south of St. Cloud, with similar amounts reported near Willmar, Atwater, and also Canby.[see: Moderate to heavy snow, February 28, 2021]
  • More noteworthy in February were the temperatures. An arctic outbreak affected a good part of the middle of the country from February 6 to February 20. A warm start and a moderating finish couldn't counter the cold spell. The preliminary average statewide temperature was 6.5 degrees or 8.9 degrees below normal. February 2021 was warmer than 2014, 2015 and 2019. The coldest temperature found in February 2021 was -50 east of Ely on February 13 and 14th and the warmest temperature was 57 degrees on February 28 at Rushford.
    [see: Minnesota Climate Trends  |  February 2021 Climate Summary Table  |  2021 February Departure from Normal Temperature Map ]

Where we stand now:

  • The snow depth ranking for February was generally below the median during the month. Mid-month saw some of the deepest snow cover of the season thus far, with eight to twelve inches over the south and one to two feet of snow over the arrowhead. With warmer conditions by the end of the month the snow pack began to erode in earnest and by March 9, a large part of western and southern Minnesota was free of snow cover.
    [see: Weekly Snow Depth and Ranking Maps  |  NWS Snow Depth Estimation Map  |  Midwest Regional Climate Center Snow Depth Map]
  • The U. S. Drought Monitor map released on March 4, 2021 depicts the entire state with some level of drought designation. Last year at this time the state was free of any drought. About 60% of the state was Abnormally Dry, and 40% of the state in Moderate Drought conditions. A small area in Rock County in southwest Minnesota and another in the northwest corner of Kittson County had Severe Drought conditions. The U.S. Drought Monitor index is a blend of science and subjectivity where drought categories (Moderate, Severe, etc.) are based on several indicators.
    [see: Drought Conditions Overview]
  • The U.S. Geological Survey reports that stream discharge values (where winter measurements are possible) are normal to much above the historical median for the date for the few Minnesota rivers that have data. Some streams have below normal discharge values in the northeast. Rivers in general are responding to the snow melt with a slow rise.
    [see: USGS Stream Flow Conditions]
  • In their final report of the 2019 growing season (November 25), the Agricultural Statistics Service reported that topsoil moisture across Minnesota was 0 percent Very Short, 1 percent Short, 64 percent Adequate, and 35 percent Surplus. History has shown that soil moisture conditions observed in the late autumn are indicative of conditions to be expected when the soil thaws. Soil moisture readings at Waseca and at Lamberton finished above the historical median for the final report for 2019. Soil temperatures at the U of M St. Paul Campus Climate Observatory have stayed near 32 degrees at the four inch depth throughout much of the winter.
    [see: Agricultural Statistics Service Crop Progress and Condition  |  U. of M. Southwest Research & Outreach Center (Lamberton)  |  U. of M. Southern Research & Outreach Center (Waseca)]
  • The potential for wildfires is currently rated by DNR Forestry as Low across northern, central and southeast Minnesota and High across southwest and south central Minnesota.
    [see: Fire Danger Rating Map]
  • Frost depths vary quite a bit from eight inches or less in southwest Minnesota, to around a foot in the south central and southeast. At Lamberton, the frost is out over sod, with still a lens of frost between 9-30 inches under bare ground. In east central Minnesota the frost is around a foot and a half. In west central Minnesota, frost depth is closer to two feet and in northeast Minnesota, there is nearly three feet of frost. Frost depth can be highly variable. Dirt roads and exposed ground are thawing in the daytime with some re-freezing at night. Typically the maximum frost depth occurs near the end of February.
    [see: National Weather Service Frost Depth Data  |  MnDOT Road Frost Depths  |  Minnesota Department of Agriculture Six-Inch Soil Temperature Network.]
  • Minnesota lakes and wetland complexes continue to be ice covered, but some streams are opening up. The median date for lake ice to leave lakes in far southern Minnesota is late March. Lake and river ice is never completely safe. There was rapid ice formation on Lake Superior during the month. On February 12, Lake Superior had 14% ice cover. By February 19 Superior was 50% covered. As fast as it formed, it faded away. On March 8, Lake Superior was 14.9% covered by ice. The maximum ice coverage for Lake Superior typically happens in late February.
    [see: DNR Conservation Officer Reports  |  Median Lake Ice-Out Dates  |  Great Lakes Ice Cover ]

Future prospects:

  • The March precipitation outlook has equal chances for below normal and above normal precipitation for all but the northeast, where there is a tilt toward above normal precipitation. Historically, average March precipitation totals range from near three-quarters of an inch in northwestern Minnesota to around two inches in southern sections of the state. March is a transition month when cold, dry continental air masses are gradually replaced by warm, moist air on a more frequent basis. This is demonstrated by the fact that March's normal precipitation is 50 percent higher than February's normal precipitation, the greatest percentage increase between any two successive months.
    [see: Climate Prediction Center 30-day Outlook  | March Precipitation Normal Map]
  • The March temperature outlook indicates a high likelihood for above normal temperatures. Normal March high temperatures climb from near 30 degrees early in the month to the low to mid-40s by month's end. Normal March lows begin the month in the single digits above zero in the far north and mid-teens in the south. By late March, normal lows are in the low 20s in the north, near 30 in the south.
    [see: Climate Prediction Center 30-day Outlook  | March Temperature Normal Map]
  • The 90-day precipitation outlook for March through May indicates equal chances for below, normal and above normal precipitation in the west with slightly better odds of above normal precipitation for the eastern part of the state, especially in the northeast. The March through May temperature projection indicates equal chances for below, normal and above normal temperatures for the north and central, with a slightly better chance for above normal temperatures in the south.
    [see: Climate Prediction Center 90-day Outlook]
  • The National Weather Service produces long-range probabilistic river stage and discharge outlooks for the Red River, Minnesota River, and Mississippi River basins. These products address both high flow and low flow probabilities. Here are the current weather conditions impacting prospects for spring snow melt flooding:
    • overall, the risk for spring flooding remains lower than a typical year throughout Minnesota.
    • on February 22, there was less than an inch of water in the snowpack over western Minnesota and around two inches in eastern Minnesota. By early March, much of the snow pack was gone over southern and western Minnesota.
    • with the current snow melt, rivers are on the rise across the state.
    • moisture in soil profiles were close to average at freeze-up in 2020.
    • frost depths range from about a foot or less in the southwest, to a foot and a half in the east and up to two feet in the west central and up to three feet in the northwest.
    [see: National Weather Service - North Central River Forecast Center]

From the author:

  • While the 2020-21 meteorological winter (December-February) finished above normal for the year, the arctic outbreak was a cold island in an otherwise balmy winter. The Twin Cities International Airport logged 116 hours of zero or colder, the longest stretch since a cold episode in January 1994. International Falls stayed at zero or colder for nine straight days, or the 5th such longest stretch on record. The 2021 outbreak was noteworthy for longevity and how late it was in the season. It also served as a spoiler of sorts to knock the winter of 20-21 out of the top ten warmest and finished tied for the 19th warmest (1895-2021).

[see: February 2021 Cold Outbreak]

Upcoming dates of note:

  • March 18: National Weather Service releases 30/90 day temperature and precipitation outlooks

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Pete Boulay, DNR Climatologist

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