HydroClim Minnesota for Early April 2013

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: April 4, 2013

What happened in March 2013:

  • March precipitation totals were near to above historical averages for most Minnesota counties except for southwest Minnesota where monthly precipitation totals fell short of the historical monthly average.
  • The first three weeks of March 2013 featured a number of late-winter snow events. One of the more noteworthy storms of the month dropped over eight inches of snow across much of Minnesota on March 4 and 5. In another event, snow and high winds led to significant travel difficulties during a winter storm that occurred March 17-19.
  • March average monthly temperatures in Minnesota were four to ten degrees below the historical average. It was Minnesota's second consecutive month of below-average monthly temperatures. Extremes for the month ranged from a low of -29 degrees at Embarrass (St. Louis County) on the 17th, to a high of 61 degrees on the 29th at Pipestone (Pipestone County) and Marshall (Lyon County).

Where we stand now:

  • Year-to-date precipitation totals top historical averages in nearly all areas except for southwest Minnesota. 2013 year-to-date precipitation totals exceed historical averages by more than two inches along a 75 mile-wide band centered along a transect from Wilkin County to northwest St. Louis County.
  • The U. S. Drought Monitor, released on April 4, places portions of northwest, west central, central, southwest, and south central Minnesota in the Extreme Drought category. Much of the rest of Minnesota is deemed to be in Severe Drought. In total, 67% of Minnesota's landscape is in Extreme Drought or Severe Drought. This is down from 84% in late January. The drought situation in northwest Minnesota is the result of a historically dry autumn in 2011, a snow-sparse 2011-2012 winter, and a dry 2012 growing season. The moisture deficits elsewhere in Minnesota developed rapidly due to very hot and very dry conditions that began in late-June and continued through autumn 2012. In southwest and south central Minnesota, June 2012-through-March 2013 precipitation totals were more than 10 inches below the historical average. The U. S. Drought Monitor index is a blend of science and subjectivity where drought categories (Moderate, Severe, etc) are based on several indicators.
  • Snow depths range from zero in the southern one-third of Minnesota to over 20 inches west central Minnesota, north central Minnesota, and in the Lake Superior highlands.
  • The amount of water content in the snow pack is estimated to be in excess of five inches in some west central and north central Minnesota counties. The large amount of water on the landscape, lying upon an impervious frozen surface, has led to a high risk for major flooding in the Red River basin.
  • The U.S. Geological Survey and Minnesota DNR report that stream discharge values vary widely across the state. After the initial flush of snow melt runoff recedes, stream discharge values will quickly fall below historical medians unless there is a very wet spring.
  • Water levels on most Minnesota lakes are low due to the dry summer and autumn of 2012. Lake Superior's water level is approximately one foot lower than its historical average for this time of year.
  • In their final report of the 2012 growing season, the Minnesota Agricultural Statistics Service reported that topsoil moisture was 27% Very Short, 42% Short, 29% Adequate, and 2% Surplus across Minnesota. Subsoil moisture was said to be 88% Very Short or Short. Soil moisture measurements made during November at University of Minnesota Research and Outreach Centers indicated extraordinarily dry conditions in the soil profile. Soil moisture content in the top five feet of soil at these locations was near all-time low values. Ample early-spring rains are critically needed to replenish soil moisture reserves before the commencement of the 2013 growing season.
  • Soil frost depth is highly variable across Minnesota (8 to 40 inches). The soil is frozen solidly and deeply in most locations. In southern Minnesota counties free of snow cover, the soil is slowly beginning to thaw from the top. Typically the soil will thaw from both top and bottom, leaving a frozen lens around 12 to 18 inches below the surface to thaw last.
  • Minnesota lakes are ice covered. The historical median lake ice-out date for far southern Minnesota is around April 1. Typically, lake ice-out progresses northward during the month of April with Minnesota/Canada border lakes losing their ice around May 1. The present thickness of lake ice and the absence of warm temperatures in the weather forecast imply that lake ice-out dates will be later than average. This marks a sharp contrast with 2012 when Minnesota's lakes lost their ice remarkably early.
  • The potential for wildfires is currently rated by DNR Forestry as Low across Minnesota. Historically, 80 percent of all wildfires in Minnesota occur during April and May.

Future prospects:

  • The April precipitation outlook offers equal chances of below-normal, near-normal, or above-normal conditions across Minnesota. April precipitation normals range from one and one-half inch in northwest Minnesota to around three inches in southeast counties. The historical probability of measurable precipitation for any given day in April ranges from 20 percent in the far northwest to 35 percent in the southeast.
  • The April temperature outlook favors below-normal conditions in the northern two-thirds of Minnesota, and equal chances of below-normal, near-normal, or above-normal conditions elsewhere in the state. Normal April high temperatures are in the mid to upper 40s early in the month, rising to the low 60s by month's end. Early April normal low temperatures are near 20 in the north, near 30 in the south. By month's end, low temperatures average in the mid 30s in the north, near 40 in the south.
  • The 90-day precipitation outlook for April through June projects above-normal conditions for the southeast  Minnesota, with equal chances of below-normal, near-normal, or above-normal conditions elsewhere in the state. The April through June temperature projection tilts towards above-normal conditions in the southern one-third of the state, and offers equal chances of below-normal, near-normal, or above-normal conditions elsewhere.
  • 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. The most recent outlooks indicate a high risk for major flooding along Red River and a risk for minor flooding in a few other Minnesota watersheds.

From the author:

  • The deeply and solidly frozen soil assured that little overwinter precipitation made it into the ground. As of late autumn, the soil moisture content in the plant rooting zone was near all-time low levels at many locations. Without abundant spring rains, a number of critical drought issues involving agriculture, forestry, horticulture, tourism, and public water supply will begin to emerge.

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Greg Spoden, DNR Climatologist

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