HydroClim Minnesota - March 2012

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

State Climatology Office - DNR Division of Ecological and Water Resources, St. Paul
prepared: March 7, 2012

What happened in February 2012:

Many drought-stricken Minnesota counties received above-normal precipitation in February 2012. Monthly precipitation totals topped the historical average by more than one inch over most of southern Minnesota. For numerous southern Minnesota locales, February 2012 was among the five wettest Februaries in the historical record. However, this welcome precipitation only partially mitigated the very large moisture deficits built up during the late summer and autumn of 2011. A continuation of above-normal precipitation patterns will be required in order to improve the drought situation.
[see: February 2012 Climate Summary Table | February 2012 Precipitation Totals Map | February 2012 Precipitation Departure from Normal Map | February 2012 Precipitation Historical Rank Map]
Two notable precipitation events came at the end of February. On February 26, much of the northern one-half of Minnesota received four to eight inches of snow. A large, moisture-laden storm swept across the southern two-thirds of Minnesota on February 28 through March 1. Rainfall amounts of over one and one-half inches were reported in many southern Minnesota communities. The rain changed to snow in central and northern Minnesota during the early-morning hours of February 29. Reports of eight or more inches of moisture-laden snow were common in central and northeastern Minnesota. Many all-time high Leap Day precipitation records were set.
[see: Leap Day Rain and Snow]
Monthly mean temperatures for February 2012 were very warm, topping the historical average by five to eight degrees across Minnesota. It was the fifth consecutive month of abnormally warm temperatures. Preliminary data indicate that the state-average temperature for the meteorological winter (December, January, and February) will likely rank among the warmest winters on record. Extreme temperature values for February ranged from a high of 55 degrees F at numerous western and southwest Minnesota locations on the 1st, to a low of -20 degrees F at Fosston (Polk County) on the 11th.
[see: February 2012 Climate Summary Table]

Where we stand now:

The U. S. Drought Monitor, released on March 1, depicts nearly every Minnesota county as experiencing some level of drought. A section of northeast Minnesota is placed in the Severe Drought category. Stream flow and lake levels in those areas are very low due to the ongoing impact of precipitation deficits accrued during the 2010 growing season and spotty precipitation in 2011. The Drought Monitor also places much of southern Minnesota in the Severe Drought category. Nearly all other Minnesota locales are determined to be in Moderate Drought. As a state, the autumn of 2011 was the driest in Minnesota's modern climate record. Above-normal February precipitation in southern Minnesota only partially mitigated the very large moisture deficits built up during the late summer and autumn of 2011. A continuation of above-normal precipitation patterns will be required in order to improve the drought situation. 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: U.S. Drought Monitor | Minnesota Drought Condition Summary]
The present snow depth across the northern one-half of Minnesota ranges from four to eight inches. Some north central and northeast Minnesota stations report more than eight inches of snow cover as of this writing. A few spots in northeast Minnesota along the Canadian border and along the Lake Superior Highlands have 12 to 18 inches of snow on the ground. Elsewhere in Minnesota, snow depths are generally one to three inches, with many locations reporting a snow-free landscape.
[see: NWS Snow Depth Estimation Map | Snow Depth Maps]
The U.S. Geological Survey reports that stream discharge values (where winter monitoring is possible) are very low in northeast and north central Minnesota watersheds. Stream flow values rank below the 5th percentile for this time of year for rivers in the northern tier of Minnesota counties. For the Red River and some of its tributaries, river flow measurements are above the median when compared with historical data for the date, the lingering impact of a wet autumn 2010 and spring 2011. Elsewhere, stream discharge is near to above normal, indicating runoff from last week's rain/snow event.
[see: USGS Stream flow conditions]
The Lake Superior water level is up two inches from its elevation of a year ago, but down 11 inches from the long-term seasonal average. Water levels on many Minnesota lakes are low when compared with historical averages.
[see: Corps of Engineers Great Lakes Water Levels | White Bear Lake Water Level | Lake of the Woods Control Board Basin Data]
In their final report of the season (November 7), the Minnesota Agricultural Statistics Service reported that topsoil moisture was 28% Very Short, 43% Short, 29% Adequate, and 0% Surplus across the state. Dry soils have heightened concerns about the soil moisture profile for the coming growing season. Late-autumn conditions act as a predictor of the soil moisture situation entering a growing season.
[see: Agricultural Statistics Service Crop Progress and Condition | U. of M. Southwest Research Center (Lamberton) Soil Moisture | U. of M. Southern Research Center (Waseca) Soil Moisture]
The soil is frozen 18 to 28 inches deep at most Minnesota reporting stations. Frost depths typically reach their maximum in late February or early March.
[see: Corps of Engineers Snow, Ice, Frost Data | MnDOT Road Frost Depths | National Weather Service Frost Depth Data]
Minnesota lakes are ice covered. However, ice conditions are highly variable. Lake and river ice is NEVER completely safe for walking or driving.
[see: DNR Conservation Officer Reports]
The potential for wildfires is currently rated by DNR Forestry as Low across Minnesota. It is unusual to discuss wildfire danger in early March. However, burning permits are required whenever there is less than 3 inches of continuous snow surrounding the burn area. A snow-sparse winter has produced this scenario in many counties.
[see: Fire Danger Rating Map]

Future prospects:

The March precipitation outlook favors above-normal conditions across most of 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.
[see: Climate Prediction Center 30-day Outlook | March Precipitation Normal Map]
The March temperature outlook tilts towards above-normal conditions, especially in southeast Minnesota. Normal March high temperatures climb from the upper 20s 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 offers an equal likelihood of below-normal, near-normal, or above-normal conditions across the state. The March through May temperature projection leans towards above-normal conditions throughout Minnesota.
[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. The probability of significant spring flooding in any Minnesota basin is currently thought to be low.
[see: National Weather Service - North Central River Forecast Center]

From the author:

Without ample, widespread precipitation in the late winter and early spring, Minnesota will face a number of drought-related issues at the beginning of the 2012 growing season. The drought situation will become rapidly apparent in the spring in the form of wildfire potential, deficient soil moisture supplies, and low water levels in wetlands, lakes, and rivers.

Notes from around the state:

None

Upcoming dates of note:

March 15: National Weather Service releases 30/90 day temperature and precipitation outlooks

Web sites featured in this edition:

http://climate.umn.edu - Minnesota Climatology Working Group, Minnesota DNR Eco/Water Resources and U of M Dept. of Soil, Water, and Climate
http://www.drought.unl.edu - National Drought Mitigation Center
http://www.nohrsc.noaa.gov - National Weather Service, National Operational Hydrologic Remote Sensing Center
http://water.usgs.gov/cgi-bin/dailyMainW?state=mn&map_type=weekd - U.S. Geological Survey
http://www.lre.usace.army.mil - US Army Corps of Engineers, Detroit District
http://mndnr.gov/waters - Minnesota Department of Natural Resources, Division of Ecological and Water Resources
http://lwcb.ca/ - Lake of the Woods Control Board
http://www.nass.usda.gov - USDA, National Agricultural Statistics Service
http://swroc.cfans.umn.edu - University of Minnesota, Southwest Research and Outreach Center, Lamberton
http://sroc.cfans.umn.edu - University of Minnesota, Southern Research and Outreach Center, Waseca
http://www.mvp-wc.usace.army.mil - U.S. Army Corps of Engineers, St. Paul District
http://www.dot.state.mn.us/materials/index.html - Office of Materials & Road Research, MnDOT
http://www.crh.noaa.gov/ncrfc - National Weather Service, North Central River Forecast Center
http://mndnr.gov/enforcement - Minnesota Department of Natural Resources, Division of Enforcement
http://mndnr.gov/forestry - Minnesota Department of Natural Resources, Division of Forestry
http://www.cpc.ncep.noaa.gov - National Weather Service, Climate Prediction Center

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