HydroClim Minnesota - August 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: August 4, 2010

What happened in July:

July 2010 rainfall totals fluctuated widely across Minnesota. July rainfalls totals ranged from less than two inches in southern Lake County and southern St. Louis County, to over ten inches in northern Otter Tail County. Historically, average July rainfall totals vary from just over three inches in northwestern Minnesota to just over four inches in eastern Minnesota counties. Very heavy July rainfall was also reported in portions of Beltrami, Koochiching, Itasca, St. Louis, Becker, Wadena, Cass, Douglas, Todd, Jackson, Martin, and Mower counties.
[see: July 2010 Climate Summary Table | July Rainfall - Departure from Normal | July Rainfall Facts for International Falls]
Outbreaks of severe weather and/or heavy rain occurred frequently during July. Tornadoes, hail, damaging winds, and flooding rains were reported in Minnesota on July 1, 3, 10, 13, 14, 17, and 27.
[see: Heavy Rains: July 1 | Heavy Rains: July 3 | Severe Weather: July 14 | Severe Weather: July 17 | Severe Weather: July 27]
Monthly mean temperatures for July 2010 were near, to somewhat above, historical averages across Minnesota. July temperatures were generally one to three degrees above normal. Extreme temperature values for July ranged from a high of 98 degrees at Browns Valley and Wheaton on the 17th, to a low of 35 degrees at Embarrass on the 1st.
[see: July 2010 Climate Summary Table | July Temperatures Facts for Duluth]

Where we stand now:

Growing season precipitation totals through early August are near, to well above, historical averages in most Minnesota communities. Large sections of the state report growing season rainfall totals that rank above the 75th percentile when compared with the historical record for the same April 1-to-present time interval. In some west central and northern Minnesota locales, seasonal precipitation totals rank among the highest in the modern record. Total seasonal rainfall in these areas has topped the historical average by six or more inches. There have been geographically-isolated exceptions to this generally wet pattern. Seasonal precipitation totals have fallen short of average in portions of Minnesota's Arrowhead region, and a small section of west central Minnesota. In these areas, less than 10 inches of precipitation was reported from mid-March through early August, a two to four inch negative departure from average. The high degree of spatial variability is best demonstrated in west central Minnesota. Beginning in mid-March, precipitation totals in north central Otter Tail County exceed 22 inches; whereas only 30 miles to the southwest, precipitation totals for the same period are less than 12 inches.
[see: Weekly and Seasonal Precipitation Maps | Dry Weather, Northeast MN]
The U. S. Drought Monitor, released on July 29, depicts all of Cook County and portions of Lake and St. Louis counties as undergoing Severe drought. Other northeastern Minnesota counties are considered to be under the influence of Moderate drought. Although the U.S. Drought Monitor no longer depicts drought in east central Minnesota, some hydrologic systems in this area remain impacted by long-term dryness that began in June of 2008. This long-term precipitation anomaly is responsible for low water levels in larger lakes and wetland complexes across Anoka, Ramsey, Chisago, and Washington counties. The rest 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 in northeastern Minnesota watersheds are below the 5th percentile when compared with historical data for the date. Stream levels are high to very high in many other Minnesota basins.
[see: USGS Streamflow | DNR Streamflow]
The Lake Superior water level is down six inches from last year at this time and remains below the long-term average. Water levels on some northern, central, and east central lakes are below average. Water levels on a few larger lakes in east central Minnesota lakes remain exceptionally low. White Bear Lake, on the Ramsey/Washington county border, is near its all-time record low level.
[see: Corps of Engineers Great Lakes Water Levels | White Bear Lake Water Level]
As of August 1, the Minnesota Agricultural Statistics Service reports that topsoil moisture was 0% Very Short, 3% Short, 80% Adequate, and 17% Surplus. 90 percent of Minnesota's corn crop is considered to be in Good or Excellent condition. 87 percent of soybeans were rated Good or Excellent.
[see: Agricultural Statistics Service Crop Progress and Condition | U. of M. Southwest Research Center (Lamberton) Soil Moisture]
The potential for wildfires is currently rated by DNR Forestry as Low throughout Minnesota.
[see: Fire Danger Rating Map]

Future prospects:

The August precipitation outlook shows no significant tendencies away from historical climatological probabilities in most Minnesota locales. However, the August outlook leans towards above-normal rainfall in far southwestern Minnesota. August precipitation normals range from under three inches in northwestern and west central Minnesota to over four and one half inches in southeastern counties.
[see: Climate Prediction Center 30-day Outlook | August Precipitation Normal Map]
The August temperature outlook leans strongly towards above-normal conditions across Minnesota. Normal August high temperatures are around 80 degrees to start the month, dropping to the mid-70s by month's end. Normal lows are around 60 degrees early in the month, falling to the mid-50s by late August
[see: Climate Prediction Center 30-day Outlook | August Temperature Normal Map]
The 90-day precipitation outlook for August through October shows no significant tendencies away from historical climatological probabilities in the eastern two-thirds of Minnesota. The outlook depicts a tilt towards above-normal August through October precipitation for western Minnesota. The August through October temperature projection tilts towards above-normal temperatures across most of Minnesota. The exception is southwestern Minnesota where the outlook offers equal chances of above-normal, near-normal, and below-normal conditions for the 90-day period.
[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:

Two of Minnesota's important agricultural commodities, corn and soybeans, are enjoying an excellent growing season. An early plant, ample rain, and adequate heat unit accumulations have created a situation where yield potential is very high.

Notes from around the state:

None

Upcoming dates of note:

August 19: National Weather Service releases 30/90 day temperature and precipitation outlooks
September 16: Kuehnast Lecture

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.crh.noaa.gov/dlh - National Weather Service, Duluth Weather Forecast Office
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://swroc.cfans.umn.edu - University of Minnesota Southwest Research and Outreach Center, Lamberton
http://mndnr.gov/forestry - Minnesota Department of Natural Resources, Division of Forestry
http://www.cpc.ncep.noaa.gov - National Weather Service, Climate Prediction Center
http://www.crh.noaa.gov/ncrfc - National Weather Service, North Central River Forecast Center

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