HydroClim Minnesota - October 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: October 6, 2010

What happened in September:

September 2010 rainfall totals were exceptionally high across much of Minnesota. A preliminary analysis of monthly rainfall totals indicates that September 2010 was the wettest September in Minnesota's modern climate record. The state-average September rainfall total was 6.46 inches, topping the previous high of 6.20 inches from 1900. By far, the biggest contribution to the new state-wide record came from the southern one-third of Minnesota where monthly totals in excess of ten inches were common. For much of southern Minnesota, September rainfall totals exceeded the historical average by five or more inches. When compared with other Septembers in the historical record, September 2010 rainfall ranked near or above all-time high values for nearly every location in the southern three tiers of Minnesota counties.
[see: September 2010 Climate Summary Table | Record Wet September]
September's heavy rainfall totals were primarily the result of an extraordinary rainfall event that occurred on September 22 and 23. More than six inches of rain fell over a 5000 square mile area of southern Minnesota. Rainfall totals of more than eight inches were reported in portions of 10 counties. The heavy rain, falling on soils already sodden from a wet summer, led to numerous reports of major rural and urban flooding. For many monitoring locations in southern Minnesota, stream discharge resulting from the deluge was the highest ever seen during an autumn flood event.
[see: Heavy Rains: September 22-23 | Heavy Rains and Severe Storms: September 2]
Monthly mean temperatures for September 2010 were somewhat cool across Minnesota, falling short of the historical average by one to three degrees. Extreme temperature values for September ranged from a high of 90 degrees at a few southwestern Minnesota locations on the 20th, to a low of 22 degrees at Brimson and Embarrass on the 26th.
[see: September 2010 Climate Summary Table]

Where we stand now:

Magnified by the wet September, warm season precipitation totals are well above historical averages in nearly all Minnesota communities. Large sections of the state report growing season rainfall totals that rank above the 90th percentile when compared with the historical record for the same April 1-to-present time interval. In some locales, seasonal precipitation totals are near, or above, all-time highs. Total seasonal rainfall in these areas has topped the historical average by eight or more inches, the statistical equivalent of receiving two extra summer months worth of precipitation. There is a geographically-isolated exception to this generally wet pattern. Seasonal precipitation totals have fallen short of average in portions of Minnesota's Arrowhead region. In these areas, less than 18 inches of precipitation was reported from mid-March through late September, a two to five inch negative departure from average.
[see: Weekly and Seasonal Precipitation Maps | Wet September | Wet Summer | Dry Weather, Northeast MN]
The U. S. Drought Monitor, released on September 30, depicts all of Cook County and portions of Lake County as undergoing Severe drought. Other northeastern Minnesota areas are considered to be under the influence of Moderate drought or are Abnormally Dry. 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 at many Red River, Minnesota River, and Mississippi River monitoring locations are at all-time highs for the date. Conversely, stream discharge values for some northeastern Minnesota rivers are below the 10th percentile when compared with historical data for the date.
[see: USGS Streamflow | DNR Streamflow]
The Lake Superior water level is down seven inches from last year at this time and down 11 inches from the long-term October 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 up only slightly from its all-time record low level mark set in mid-September.
[see: Corps of Engineers Great Lakes Water Levels | White Bear Lake Water Level]
As of October 3, the Minnesota Agricultural Statistics Service reports that topsoil moisture was 0% Very Short, 0% Short, 53% Adequate, and 47% Surplus. 86 percent of Minnesota's corn crop is considered to be in Good or Excellent condition. 84 percent of soybeans were rated Good or Excellent. In several counties, fields have dried rapidly allowing fieldwork to resume.
[see: Agricultural Statistics Service Crop Progress and Condition]
The potential for wildfires is currently rated by DNR Forestry as Moderate throughout the northern two-thirds of Minnesota due to recent dry weather and sunny skies. The fire danger rating is Low in the southern one-third of Minnesota.
[see: Fire Danger Rating Map]

Future prospects:

The October precipitation outlook depicts no significant tendencies away from historical climatological probabilities in most Minnesota locales. For a few southwestern Minnesota counties, the outlook tilts towards below-normal precipitation. Normal October precipitation ranges from one and one half inches in northwestern Minnesota, to over two and one half inches in portions of north central and northeastern Minnesota.
[see: Climate Prediction Center 30-day Outlook | October Precipitation Normal Map]
The October temperature outlook indicates a strong tendency towards above-normal temperatures throughout Minnesota. Normal October high temperatures fall from the low to mid 60s early in the month, to the upper 40s by month's end. Normal October low temperatures drop from the low 40s early in the month to near 30 by late October.
[see: Climate Prediction Center 30-day Outlook | October Temperature Normal Map]
The 90-day precipitation outlook for October through December shows no significant tendencies away from historical climatological probabilities across Minnesota. The October through December temperature projection tilts towards above-normal temperatures, especially in northeastern Minnesota counties.
[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:

A note of concern from the author ... saturated soils in the Red River basin along with high autumn stream base flows enhance the possibility of spring flooding along the Red River and its tributaries in 2011.

Notes from around the state:

None

Upcoming dates of note:

October 21: 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://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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