HydroClim Minnesota - April 2010

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 Waters
compiled 4/7/2010

What happened in March:

March 2010 precipitation totals were below average nearly everywhere in Minnesota. Only in northwestern Minnesota was precipitation near the monthly average. In most locations, March precipitation fell short of average by one-half to one and one-half inches. Many communities reported a snowless March, a very rare occurrence. In the Twin Cities, the last snow-free March was in 1878.
[see: March 2010 Climate Summary Table | Snowless March]
During the second half of March, precipitation was nearly nonexistent throughout Minnesota. The lack of rain and snow was an extraordinary piece of good fortune for communities involved in the late winter/early spring flood fight. Heavy October rains, a significant winter snow pack, and a rapid snow melt produced major flooding in the Red River, Minnesota River, and Mississippi River watersheds. The dry weather during the final weeks of March kept a serious situation from becoming far worse. In spite of the dry weather, some Minnesota rivers remain at the "Moderate" flood level as of this writing.
[see: Spring Flood Information]
Monthly mean temperatures for March 2010 were well above average across Minnesota. March monthly temperature averages were four to eleven degrees above the historical mean. Extreme temperature values for March ranged from a high of 78 degrees at various southern Minnesota locations on the 31st, to a low of -9 degrees at Roseau on the 1st. Record high maximum and minimum temperatures were set on the 14th, 15th, 18th, 30th, and 31st of March at various locations around the state.
[see: March 2010 Climate Summary Table]

Where we stand now:

The snow depth map prepared on April 1 shows that there is no snow on the ground anywhere in Minnesota. Due to unusually warm temperatures and negligible March snowfall, most Minnesota locales have been free of snow cover since mid-March. This is quite unusual. In far north central Minnesota, the probability of having no snow cover on March 18 is merely one percent (one in one hundred years).
[see: Snow Depth Maps]
The U. S. Drought Monitor, released on April 1, reflects long-term precipitation deficits in a few Minnesota counties. A small area of east central Minnesota remains in the Moderate drought category due to lingering precipitation shortfalls that extend back to early-summer 2008. Impacts from these shortfalls are mostly observed in water levels on larger lakes and wetland complexes. Portions of north central and northeastern Minnesota are categorized as Abnormally Dry, the result of a very dry 2009 growing season and relatively sparse winter snowfall. Most of Minnesota is without drought designation. 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]
The U.S. Geological Survey reports that stream discharge values are high in the upper Red River basin and much of the Minnesota River basin. Stream flow values in many east central and northeastern Minnesota watersheds are below the 25th percentile when compared with historical data for the date. Elsewhere, stream discharge values are near the middle of the historical distribution for this time of year.
[see: USGS Streamflow | DNR Streamflow]
The Lake Superior water level is down two inches from last year at this time and remains below the long-term average. Water levels on many Minnesota lakes and wetlands rose markedly due to the heavy October precipitation. However, water levels on some larger lakes and wetlands complexes in east central Minnesota lakes remain very low. White Bear Lake, on the Ramsey/Washington county border, is just above its all-time record low level.
[see: Corps of Engineers Great Lakes Water Levels | White Bear Lake Water Level]
As of April 4, the Minnesota Agricultural Statistics Service reports that topsoil moisture was 6% Very Short, 9% Short, 64% Adequate, and 21% Surplus. Heavy October 2009 rains amply recharged the soil moisture profile across Minnesota. This greatly improved prospects for forestry, horticultural, and agricultural interests for the early 2010 growing season.
[see: Agricultural Statistics Service Crop Progress and Condition]
Minnesota's lakes are free of ice in most locations. Only larger, deeper lakes in north central and northeastern Minnesota remain ice covered. For many central and northern Minnesota locations, lake ice-out was ten to twenty days earlier than the long-term average. In some northern Minnesota lakes, lake ice-out was the earliest on record.
[see: Lake Ice-out Status]
Soil frost is nearly gone across Minnesota. A lens of soil frost remains in place well beneath the surface under some road surfaces in northern Minnesota. On average, the agricultural soil profile thaws by late March to early April in the south, early April to mid-April in the north. The soil thaws from both the top and the bottom, leaving a mid-layer zone of frozen soil to be the last to climb above freezing.
[see: National Weather Service Frost Depth Data | Corps of Engineers Snow, Ice, Frost Data | MnDOT Road Frost Depths]
The potential for wildfires is currently rated by DNR Forestry as "high" across the northern two-thirds of Minnesota, "low" elsewhere. These conditions can change rapidly in response to warm, sunny, and windy weather. Historically, 80 percent of all wildfires in Minnesota occur during April and May.
[see: Fire Danger Rating Map]

Future prospects:

The April precipitation outlook leans towards above-average conditions statewide. April precipitation normals range from one and one half inches in northwestern Minnesota to around three inches in southeastern 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.
[see: Climate Prediction Center 30-day Outlook | April Precipitation Normal Map]
The April temperature outlook indicates a tilt towards above-average conditions across Minnesota. 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.
[see: Climate Prediction Center 30-day Outlook | April Temperature Normal Map]
The 90-day precipitation outlook for April through June shows no significant tendencies away from climatological probabilities. The April through June temperature projection tilts towards below-average conditions in the western two-thirds of Minnesota, and is inconclusive for the eastern one-third of the state.
[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 are part of the National Weather Service's Advanced Hydrologic Prediction Service (AHPS).
[see: National Weather Service North Central River Forecast Center]

From the author:

None

Notes from around the state:

None

Upcoming dates of note:

April 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 Waters and U of M Dept. of Soil, Water, and Climate
http://www.drought.unl.edu - National Drought Mitigation Center
http://water.usgs.gov/cgi-bin/dailyMainW?state=mn&map_type=weekd - U.S. Geological Survey
http://mndnr.gov/waters - Minnesota Department of Natural Resources, Division of Waters
http://www.lre.usace.army.mil - US Army Corps of Engineers, Detroit District
http://www.nass.usda.gov - USDA, National Agricultural Statistics Service
http://www.mvp-wc.usace.army.mil - US Army Corps of Engineers, St. Paul District
http://www.crh.noaa.gov/ncrfc - National Weather Service, North Central River Forecast Center
http://www.dot.state.mn.us/materials - Minnesota Department of Transportation, Materials Engineering and Testing
http://www.cpc.ncep.noaa.gov - National Weather Service, Climate Prediction Center

To subscribe or unsubscribe to HydroClim Minnesota please notify .

Contributions of information and suggestions are welcome!