A monthly electronic newsletter summarizing Minnesota's climate conditions and the resulting impact on water resources. Distributed on the first Thursday of each month.
State Climatology Office - DNR Division of Ecological and Water Resources, St. Paul
distributed: March 7, 2013
What happened in February 2013:
- February precipitation totals were above historical averages statewide. Monthly precipitation totals topped the historical average by approximately one-half inch in many locations, and by over one inch in west central and north central Minnesota counties. February precipitation totals set new all-time high records in communities such as Breckenridge, Benson, and Rothsay.
- February 2013 featured a number of significant snow events. One of the more noteworthy weather occurrences of February was a winter storm that dropped over 18 inches of snow on portions of west central Minnesota on February 9-11. Heavy snow and high winds created travel problems throughout much of Minnesota during the event.
- February average monthly temperatures in Minnesota were two to four degrees below the historical average. For a number of communities, it was only the second time in 21 months that the mean monthly temperature was below average. Extremes for the month ranged from a low of -39 degrees at International Falls (Koochiching County) and Northome (Koochiching County) on the 2nd, to a high of 45 degrees on the 26th at Grand Rapids (Itasca County) and Big Falls (Koochiching County). The warm temperatures in northern Minnesota on the 26th were the result of the "pine tree effect", caused by solar energy absorption in the dark-colored coniferous forests and light low-level winds limiting mixing with the colder air aloft.
Where we stand now:
- Year-to-date precipitation totals top historical averages in all areas except for southwest Minnesota, and far northeast Minnesota. 2013 year-to-date precipitation totals exceed historical averages by more than one and one-half 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 March 7, places portions of northwestern, west central, central, southwestern, and south central Minnesota in the Extreme Drought category. Much of the rest of Minnesota is deemed to be in Severe Drought. In total, 70% of Minnesota's landscape is in Extreme Drought or Severe Drought. This is down from 84% in late January. A one-category improvement was assigned to some west central and north central Minnesota counties due to heavy February snowfall. 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 the autumn. For large portions of Minnesota, August 2012-through-February 2013 precipitation totals ranked below the 5th percentile historically. In southwest and south central Minnesota, June 2012-through-February 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 vary widely across Minnesota. Many locations in west central Minnesota, north central Minnesota, and in the Lake Superior highlands report more than 20 inches of snow cover. Whereas, snow depths in southwest Minnesota counties are less than six inches. Elsewhere in Minnesota, snow depths range from 15 to 20 inches. The present snow depth, when compared with other years on this date, is above the historical median in nearly all locations.
- The amount of water content in the snow pack also varies widely across Minnesota. For most of the state, the snow water content is estimated to be two to four inches. Some west central, north central, and northeast Minnesota counties report snow water equivalence values in excess of four inches. Along the southern two tiers of Minnesota counties, snow water equivalence is estimated to be less than two inches.
- The U.S. Geological Survey and Minnesota DNR report that many stream discharge values are low at Minnesota reporting locations where winter monitoring is possible. At these locations, stream flow values rank below the 25th percentile when compared with historical data for this time of year.
- Water levels on most Minnesota lakes are low due to the dry summer and autumn. 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 (October 31), 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 under sod ranges from 18 to 44 inches across Minnesota. Frost typically reaches maximum depth in late February or early March.
- Minnesota lakes and rivers are ice covered. Lake and river ice is never completely safe. Caution is always advised when venturing onto the ice.
Future prospects:
- The March precipitation outlook offers equal chances of below-normal, near-normal, or above-normal conditions across Minnesota. 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 warmer, moister 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.
- The March temperature outlook favors below-normal conditions for the state. Normal March high temperatures climb from the 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.
- The 90-day precipitation outlook for March through May projects above-normal conditions for the eastern one-half of Minnesota, with equal chances of below-normal, near-normal, or above-normal conditions for western Minnesota. The March through May temperature projection tilts towards above-normal conditions for all but northwest Minnesota, where the outlook offers equal chances of below-normal, near-normal, or above-normal conditions.
- 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 of moderate to major flooding along Red River.
From the author:
- The drought situation will remain unchanged until spring because the deeply and solidly frozen soil assures that very little winter precipitation will make 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