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HydroClim Minnesota - April 2009

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 4/7/2009 (early distribution by one day)

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What happened in March:

• March 2009 was an extraordinarily wet month across much of Minnesota. Large areas of central and northern Minnesota received three to five inches of precipitation for the month, in many cases tripling the historical monthly average. Monthly total precipitation records were set in locations such as Fargo (4.62 inches), St. Cloud (4.66 inches), and Grand Rapids (4.24 inches). By contrast, most southeastern Minnesota locales reported March precipitation totals that fell short of the historical average by approximately one inch.
  [see: March 2009 Climate Summary Table]
• Three major winter storms impacted the upper Midwest during the month of March. Heavy snow, high winds, and bitter cold temperatures pummeled northern Minnesota on March 10 and 11. During a four-day period from March 22 to March 25, a slow-moving, moisture-ladened storm dropped unprecedented, and devastating, amounts of rain, ice, and snow across much of the state. The month ended with yet another major winter storm that dropped wet, heavy snow from west central Minnesota through northeast Minnesota from March 30 through April 1.
  [see: March 10-11 Blizzard  |  March 22-25 Heavy Rain, Ice, and Snow  |  March 31 Winter Storm]
• Monthly mean temperatures for March 2009 were near to slightly below historical averages across Minnesota. Cold temperatures during the first half of the month were offset by very warm weather in the third week of March. Extreme temperature values for March ranged from a high of 69 degrees in Marshall on the 16th, to a low of -36 degrees in Embarrass (St. Louis County) on the 12th.
  [see: March 2009 Climate Summary Table]
• Major early-spring flooding occurred during the later half of March in the Red River basin and a few other Minnesota watersheds. In the Red River basin, major flooding is still underway as of this writing, and a significant secondary crest is expected. The flooding event was remarkable for its early onset, and for its unparalleled magnitude at some reporting stations. Five components are often cited as contributors to major flooding along the Red River:
      - Heavy autumn precipitation. Precipitation totals for the meteorological autumn (September through November) were far above long-term averages in the Red River basin. Precipitation values exceeded historical averages by four or more inches across most of the watershed. Both Fargo and Grand Forks set all-time autumn precipitation records for the three-month period.
      - Deeply and solidly frozen soil. Very cold temperatures in arrived in December before a significant snow cover. The cold temperatures, along with a saturated soil profile, resulted in "concrete frost", an impervious layer highly conducive to runoff.
      - Heavy winter snowfall. Record-setting snowfall totals were reported in southern sections of the Red River basin in December and in March. These totals, combined with near-average snowfall in January and February, made the snow season of 2008-2009 one of the snowiest ever in this region.
      - An unfavorable melt pattern. The middle of March brought a ten-day period of relative warmth to the Red River Valley. For eight of the ten days, temperatures climbed approximately ten degrees above the historical average. The warm weather came in conjunction with ...
      - Heavy rain on melting snow. Precipitation totals in some portions of southeastern North Dakota, central Minnesota, and northern Minnesota ranged from two to four inches for the period March 22 through March 25. For historical context, the MONTHLY NORMAL precipitation for that region is approximately one and one quarter inches. In some locations, 24-hour precipitation totals for March 23 and March 24 set all-time records for those dates. In a few cases, 24-hour precipitation totals were the greatest ever recorded for ANY March date. The four-day precipitation total at Fargo, 2.76 inches, is greater than the all-time MONTHLY March precipitation record of 2.62 (set in 1995).

Where we stand now:

• The snow depth map prepared on April 2 shows that most of the southern one-half of Minnesota is snow free. Snow depths in the northern one-half of the state exceed four inches. Sections of west central, north central, and northeastern Minnesota report more than 12 inches of snow cover.
  [see: Snow Depth Maps]
• The U. S. Drought Monitor, released on April 2, classified some Minnesota counties in the D0 - Abnormally Dry category. Portions of east central and southeastern Minnesota were placed in the D1 - Moderate Drought classification. Precipitation during the last half of 2008 was five to eight inches short of average for many southeastern Minnesota communities. The U. S. Drought Monitor index is a blend of science and subjectivity where intensity categories are based on several indicators.
  [see: U.S. Drought Monitor]
• The U.S. Geological Survey reports that stream discharge values are high in the Red River basin, in the Upper Minnesota River basin, and along the upper Mississippi River. Stream flow measurements in these areas are above the 90th percentile when compared with the historical distribution for this time of year. Stream discharge values in southeastern Minnesota are below the historical median for the date.
  [see: USGS Streamflow  |  DNR Streamflow]
• The Lake Superior water level is up six inches from last year at this time but remains below the long-term average. Levels on inland lakes in Minnesota's drought areas are low. In some cases, east central Minnesota lake levels are similar to those observed during the droughts of 2006 and 2007.
  [see: Corps of Engineers Great Lakes Water Levels]
• In their final soil moisture summary of 2008, the Minnesota Agricultural Statistics Service reported that late-November topsoil moisture was 1% "Very Short", 6% "Short", 77% "Adequate", and 16% "Surplus". Surplus soil moisture conditions are found throughout the Red River basin. Subsoil moisture supplies were reported as 2% "Very Short", 16% "Short", 71% "Adequate", and 11% "Surplus". The focus of subsoil moisture deficits is on east central and southeast Minnesota. With soils now thawed, subsoil moisture recharge will be possible with early spring precipitation.
  [see: Ag. Statistics Service Crop Progress and Condition]
• Soil frost remains in place in the northern two-thirds of Minnesota, with some thawing near the top of the profile. Frost has left the ground in most southern Minnesota locations. In areas with deep frost, the soils will thaw rapidly as the sun angle increases, the days get longer, and warm rain acts as a heat-transfer mechanism. On average, the 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 lens 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]
• Large lakes in central and northern Minnesota remain ice covered. Many lakes in the southern one-quarter of Minnesota lost their ice during the third week of March due to a spell of warm rain and high winds.
  [see: Lake Ice-Out Status]
• The potential for wildfires is currently rated by DNR Forestry as "high" in central and east central 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 offers equal chances of above, near, or below average conditions. 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 offers equal chances of below-normal, near-normal, or above-normal conditions. Normal April high temperatures are in the mid to upper 40's early in the month, rising to the low 60's 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 30's 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 indicates no significant tendencies away from climatological probabilities across Minnesota. The April through June temperature projection also offers equal chances of below, near, and 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 are part of the National Weather Service's Advanced Hydrologic Prediction Service (AHPS). The probability of major flooding in the Red River basin remains high. Elsewhere in Minnesota, flood potential is of lesser concern.
  [see: National Weather Service River Forecast Center]

From the author:

• None

Notes from around the state:

• None

Upcoming dates of note:

• April 16: 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.crh.noaa.gov/ncrfc - National Weather Service, North Central River Forecast Center
• http://www.mvp-wc.usace.army.mil - US Army Corps of Engineers, St. Paul District
• http://www.dot.state.mn.us/mnroad - Minnesota Department of Transportation, Cold Weather Road Research
• http://mndnr.gov/forestry - Minnesota Department of Natural Resources, Division of Forestry
• http://www.cpc.ncep.noaa.gov - National Weather Service, Climate Prediction Center

Acknowledgements

• None

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Last modified: April 7, 2009