HydroClim Minnesota for Early May 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: May 6, 2021
What happened in April 2021:
- The rain returned to the north half of the state in April 2021, while the southeast was left mostly dry. The wettest areas in April was a wide swath of two to four inches from Browns Valley though Grand Rapids and Duluth. The highest precipitation total found so far by an observer from the National Weather Service was Collegeville in Stearns County with 5.20 inches or 2.48 inches above normal. Ely wound up with 4.63 inches. Ottertail in west central Minnesota had 4.38 inches or 2.26 inches above normal. In the dry southeast corner of the state the lowest precipitation value found was Caledonia with .62 inches or 3.27 inches below normal. The preliminary statewide average for Minnesota was 2.22 inches or .55 inches below normal.
[see: April 2021 Precipitation Total Map | April 2021 Precipitation Departure Map | April 2021 Climate Summary Table | April 2021 Percent of Normal Precipitation Map]
- The main precipitation event of April 2021 was a 10-day period of seemingly-endless clouds and precipitation took a bite out of ongoing drought, which had been escalating through the winter and spring in Minnesota. The highest total with this event was 5.94 inches by a CoCoRaHS observer in the Sartell area, just north of St. Cloud.
[see: Wild Spring Weather Provides Much-Needed Rain]
- April featured a roller-coaster temperature ride with high heat at the start of the month, a very chilly middle and seasonable weather to end the month. The April 5th heat wave notched some of the highest temperatures recorded in early April in Minnesota. The summer-like temperatures at the start and at the end were just enough to counterbalance the spring chill and overall the state finished with a preliminary average of 43.1 degrees or .4 (four tenths) of a degree above normal. The highest temperature found was 88 degrees on April 5th at Lamberton and Redwood Falls in southwest Minnesota, the lowest temperature found was 1 degree above zero near Brimson in northeast Minnesota.
[see: Record Heat, April 5, 2021 | <April 2021 Climate Summary Table | 2021 April Departure from Normal Temperature Map
Where we stand now:
- Seasonal precipitation totals so far (April 1 through May 4) ranked well below the historical median in south central and parts of southeast Minnesota, with a large swath in the 70th percentile or above from west-central to north central and northeast Minnesota.
[see: Seasonal Precipitation, Percent Normal and Ranking Maps]
- The final snow depth map of the season was produced on April 1, as the state's snowpack dwindled. Snow depths up to 12 inches were reported on that date in parts of Cook County. The Wolf Ridge Environmental Learning Center in Lake County lost its snow cover by early April and had one final inch of snowfall on April 24. [see: Snow Depth Maps]
- The U. S. Drought Monitor map released on May 6, 2021 depicts 37% of the state with some level of drought designation. This is much improved since April. Last year at this time 4% of the state was Abnormally Dry. On May 6, 2021, about 21% of the state was Abnormally Dry, and 15% of the state in Moderate Drought conditions. A small area in Kittson and Marshall County in northwest Minnesota 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 are generally near normal across the state, with some streams below normal in the northwest, south central, and southeast. Four streams on May 6 were below the 10th percentile. These were: The Thief River near Thief River Falls, the Straight River near Park Rapids, the Knife River near Two Harbors and the South Fork Zumbro River at Rochester.
[see:USGS Stream Flow Conditions]
- Water levels on most Minnesota lakes vary depending on lake and location in the state. The Mille Lacs lake level for early May was very near the median and about a half-foot lower than this time last year. The ice left Mille Lacs on April 7, nineteen days earlier than last year and eighteen days earlier than the median. On May 5, Minnetonka was at 929.23 feet, about a tenth of a foot lower than last year. The Gray’s Bay Dam continues to be closed. It was last open on October 16, 2020. White Bear Lake was at 924.58 on May 6, (.4) four tenths of a foot lower than last year. Lake of the Woods was at its 55th percentile for April 27th, at 1058.45ft. Lake Superior was forecast to be at 602.07 feet on April 30, nine inches higher than the monthly average for late April and four inches lower than late April 2020.
[see: Mille Lacs Lake Water Level | Lake Minnetonka Water Level | White Bear Lake Water Level | Lake of the Woods Control Board Basin Data | Corps of Engineers Great Lakes Water Levels]
- A fairly dry April and early May assisted spring crop planting. 60% of the corn crop was planted by May 2. This was behind 2020, but well ahead of the five year average. The Agricultural Statistics Service reported on May 2 that topsoil moisture supplies across Minnesota are 8 percent Very Short, 27 percent Short, 60 percent Adequate, and 5 percent Surplus.
[see: Agricultural Statistics Service Crop Progress and Condition]
- This spring so far has featured occasional days with sun, heat and wind and this caused the potential for wildfires to be elevated at times. The potential for wildfires on May 6, rated by DNR Forestry as ranging from Very High over much of the west half of Minnesota, south central, central and the Duluth area. High in the northwest, north central and east central Minnesota. Moderate conditions are present in southeast and northeast Minnesota.
[see: Fire Danger Rating Map]
- Lake ice out began during the third week of March, about one to two weeks earlier than the median. Lake ice out rapidly progressed northward, with the majority of lakes in the state ice free by late April. Greenwood Lake in Cook County was the last to shed its ice on May 1. Lake ice out for many lakes were from ten days to two weeks ahead of the median.
[see: 2021 Lake Ice-Out Dates | DNR Conservation Officer Reports]
- The May precipitation outlook has equal chances of below-normal, near-normal, or above-normal conditions for the state. May precipitation normals range from just over two inches in northwest Minnesota to just less than four inches in southeastern counties. The historical probability of measurable precipitation for any given day in May ranges from 25 percent in the northwest to near 40 percent in the southeast.
[see: Climate Prediction Center 30-day Outlook | May Precipitation Normal Map]
- The temperature outlook for May calls for a tilt for below normal temperatures from the Twin Cities, through St. Cloud northwest to Grand Forks, with equal chances of below, above and normal temperatures over southwest and west central Minnesota. Normal May high temperatures are in the low to mid-60s early in the month, rising to the low to mid-70s at month's end. Normal May low temperatures are in the mid-30s to near 40 to start the month, and climb to the mid-40s to low 50s as the month ends.
[see: Climate Prediction Center 30-day Outlook | May Temperature Normal Map]
- The 90-day precipitation outlook for May through July indicates equal chances of below-normal, near-normal, or above-normal conditions across the state. The May through July temperature projection shows a broad area covering much of the United States with a tendency for above-normal conditions.
[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.
[see: National Weather Service - North Central River Forecast Center]
From the author:
- The National Centers of Environmental Information (NCEI) released the 1991-2020 normals on May 4, 2021. NCEI has Quick Access to the 1991-2020 Normals. For example: Here's 1991-2020 Normal information for the Twin Cities. This page compares the 1981-2010 Normals to the 1991-2020 Normals for the Twin Cities.
Upcoming dates of note:
- May 20: National Weather Service releases 30/90 day temperature and precipitation outlooks
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Pete Boulay, DNR Climatologist