HydroClim Minnesota - April 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: April 4, 2012

What happened in March 2012:

March 2012 precipitation totals were highly variable across Minnesota. In some northern Minnesota communities, monthly precipitation totals topped the historical March average by more than one inch. Conversely, in many west central and southern Minnesota counties, March 2012 precipitation totals were one-half inch or more short of average.
[see: March 2012 Climate Summary Table | March 2012 Precipitation Departure from Normal Map]
Two notable precipitation events came near the end of March. On March 23, a sequence of thunderstorms dropped early spring rain along a swath that extended from Grand Forks to International Falls. Portions of Marshall, Beltrami, Lake of the Woods, and Koochiching counties reported one to two inches of welcome rain. Winter made a brief return on March 28 and 29 when a storm system deposited one to five inches of snow on some far northern Minnesota communities.
Monthly mean temperatures for March 2012 were astoundingly warm, topping the historical average by 10 to 17 degrees across Minnesota. It was the six consecutive month of abnormally warm temperatures. Preliminary data indicate that March 2012 will rank as Minnesota's, and the country's, warmest March of the modern record. Hundreds of daily high temperature and daily warm low temperature records were set across Minnesota on numerous dates. The extraordinarily warm weather rapidly advanced signs of spring such as perennial plant development and lake ice out by three to four weeks. Extreme temperature values for March ranged from a high of 84 degrees F at Madison (Lac Qui Parle) on the 18th, to a low of -18 degrees F at Embarrass and Babbitt (St. Louis County) on the 5th and 6th.
[see: March 2012 Climate Summary Table | Mild March 2012 | March Madness]

Where we stand now:

The U. S. Drought Monitor, released on March 29, 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, and winter snowfall totals were quite meager. Over the last eight months, precipitation totals are short of normal by more than six inches in many Minnesota communities. 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]
There is no snow on the ground anywhere in Minnesota. Snow left by a late-March storm along some of the northern tier of Minnesota counties has melted.
[see: NWS Snow Depth Estimation Map | Snow Depth Maps]
The U.S. Geological Survey reports that stream discharge values are very low in northeast Minnesota. Stream discharge values are also very low in most southern Minnesota watersheds. Stream flow values rank below the 5th percentile for this time of year at numerous measuring points in these areas. Elsewhere in Minnesota, river flows rank near the middle of the historical data distribution for the season, but are falling. Exceptions to this overall downward trend are a few north central Minnesota rivers responding to recent, isolated heavy rainfalls.
[see: USGS Stream flow conditions | MNDNR Weekly Stream Flow Maps and Tables]
Water levels on many Minnesota lakes are low when compared with historical averages for this time of year. Lake levels on some northeast and east central Minnesota lakes rank below the 10th percentile when compared with historical lake level data for the season. The Lake Superior water level is up five inches from its elevation of a year ago, but down nine inches from the long-term seasonal average.
[see: Lake Minnetonka Water Levels | White Bear Lake Water Level | Lake of the Woods Control Board Basin Data | Corps of Engineers Great Lakes Water Levels]
In their April 2 report, the Minnesota Agricultural Statistics Service reported that topsoil moisture is 12% Very Short, 42% Short, 43% Adequate, and 3% Surplus across Minnesota. The subsoil moisture is rated 18% Very Short, 50% Short, 32% Adequate, and 0% Surplus. Dry soils have heightened concerns about the soil moisture profile for the coming 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 thawed at all Minnesota reporting stations. The soils are warming rapidly. Soil temperatures at a four-inch depth under bare soil averaged from the low 40s to near 50 degrees last week.
[see: Soil Temperature Tables | Corps of Engineers Snow, Ice, Frost Data | MnDOT Road Frost Depths | National Weather Service Frost Depth Data]
Nearly all Minnesota lakes are free of ice. Only a few larger, deeper Canadian border lakes retain some ice. Almost every lake in the southern two-thirds of Minnesota was free of ice before March 25. Most lakes in the northern one-third of Minnesota were ice-free by April 1. Lake ice out dates were three to four weeks earlier than historical averages. For the majority of Minnesota lakes, 2012 ice out dates were the earliest on record.
[see: Lake Ice Out Dates | DNR Conservation Officer Reports]
The potential for wildfires is currently rated by DNR Forestry as High for nearly all of Minnesota. A High rating indicates that "fires start easily and spread at a fast rate. All fine dead fuels ignite readily and fires start easily from most causes. Unattended campfires are likely to escape. Fires spread rapidly and short-distance spotting is common. High-intensity burning may develop on slopes, or in concentrations of fine fuel. Fire may become serious and difficult to control unless they are hit hard and fast while small." Historically, 80 percent of all wildfires in Minnesota occur during April and May.
[see: Fire Danger Rating Map]

Future prospects:

The April precipitation outlook projects equal chances of above-normal, near-normal, and below-normal conditions. 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.
[see: Climate Prediction Center 30-day Outlook | April Precipitation Normal Map]
The April temperature outlook tilts heavily towards above-normal conditions, especially in southern 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. Agricultural and horticultural interests should note that a warm March offers no indication of when Minnesota locales will experience the last frost date of spring. The median date of the final occurrence of 32 degrees or less in the spring ranges from near May 1 in far southern Minnesota and the metropolitan heat island, to the last week of May in the far north.
[see: Climate Prediction Center 30-day Outlook | April Temperature Normal Map | Median Frost Dates | Date of Final Spring Frost]
The 90-day precipitation outlook for April through June offers an equal likelihood of below-normal, near-normal, or above-normal conditions across the state. The April through June temperature projection also indicates an equal likelihood of below-normal, near-normal, or 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:

Without ample, widespread precipitation in the spring, Minnesota will face a number of drought-related issues during the 2012 growing season. The drought situation will become rapidly apparent in the form of wildfire potential, deficient soil moisture supplies, and low water levels in wetlands, lakes, and rivers. Defining "ample, widespread precipitation" is subjective. However, as a general rule-of-thumb, the total amount of April-plus-May precipitation needed to reduce drought impacts is around five to seven inches, falling over large sections of the state. This is roughly two inches above historical averages for the two-month period.

Notes from around the state:

None

Upcoming dates of note:

April 19: 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://water.weather.gov/precip/ - National Weather Service, Advanced Hydrologic Prediction Service
http://www.esrl.noaa.gov - NOAA, Earth System Resource Laboratory
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://mndnr.gov/waters - Minnesota Department of Natural Resources, Division of Ecological and Water Resources
http://www.minnehahacreek.org - Minnehaha Creek Watershed District
http://lwcb.ca/ - Lake of the Woods Control Board
http://www.lre.usace.army.mil - US Army Corps of Engineers, Detroit District
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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