HydroClim Minnesota - September 2012

A monthly electronic newsletter summarizing Minnesota's climate conditions and the resulting impact on water resources. Distributed on the Thursday following the first Monday of each month.

State Climatology Office - DNR Division of Ecological and Water Resources, St. Paul
prepared: September 6, 2012

What happened in August 2012:

With a few exceptions, August 2012 monthly precipitation totals were very low across Minnesota, especially in the eastern one-half of the state. August rainfall totaled one to three inches in most locations, falling short of historical averages by one to two and one-half inches. A few areas received August downpours of three to five inches in just a few hours. However, these areas were very small in geographic extent and the heavy rain did little to impact the overall drought situation.
[see: August 2012 Climate Summary Table | August 2012 Monthly Precipitation Map | August 2012 Precipitation Departure from Normal Map]
Monthly mean temperatures for August 2012 were very close to the historical average throughout Minnesota. Preliminary data indicate that the statewide average was just a tenth of a degree F below the normal. The streak of ten consecutive months of above-normal statewide temperatures may have come to end, but only by a whisker. The preliminary data also show that the statewide average temperature for the summer season (June-August) was among the ten warmest on record. Extreme temperature values for August ranged from a high of 102 degrees F at Canby (Yellow Medicine County) on the 1st; to a low of 33 degrees F at Embarrass (St. Louis County) on the 17th, 18th, and 19th; and at Brimson (St. Louis County) on the 19th.
[see: August 2012 Climate Summary Table]

Where we stand now:

The U. S. Drought Monitor, released on September 6 places portions of southwestern and south central Minnesota in the Extreme Drought category. Many northwestern Minnesota counties, and many of Minnesota's southernmost counties are said to be in Severe Drought. In total, approximately 63 percent of Minnesota is considered to be in the Abnormally Dry category or worse. The drought situation in northwest Minnesota and in far southeast Minnesota is the result of an historically dry autumn in 2011, a snow-sparse winter, and a dry 2012 growing season. The moisture deficits in southern Minnesota developed rapidly due to very hot and very dry conditions that began in late June and continue as of this writing. Over the past 11 weeks, rainfall totals in many Minnesota counties fell short of average by four or more inches. This is the climatological equivalent of missing an entire summer's month worth of precipitation. In some south central Minnesota communities, late summer rainfall deficits are in excess of six inches. 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: Minnesota Drought Condition Summary | Red River Basin Drought Decision Support System]
The U.S. Geological Survey and Minnesota DNR report that stream discharge values are very low at numerous Minnesota reporting locations. Stream flow values rank below the 10th percentile for this time of year in some of these watersheds.
[see: USGS stream flow conditions | MNDNR Weekly Stream Flow Maps and Tables]
Water levels on many Minnesota lakes are very low in response to the dry, hot summer. Lake Superior water level is similar to the 2011 level at this time of year, but below the long-term average for the date.
[see: Lake Minnetonka Water Levels | White Bear Lake Water Levels | Lake of the Woods Control Board Basin Data | Corps of Engineers Great Lakes Water Levels]
In their September 2 report, the Minnesota Agricultural Statistics Service reported that topsoil moisture was 22% Very Short, 41% Short, 37% Adequate, and 0% Surplus across Minnesota. This represents a significant degradation in conditions when compared with an early-June soil moisture survey reporting only 5% of the landscape Short or Very Short. Soil moisture measurements from University of Minnesota Research and Outreach Centers indicate extraordinarily dry conditions in the top three feet of the soil profile. Ample autumn rains are critically needed to replenish soil moisture reserves. The Agricultural Statistics report also indicates that roughly 85% of Minnesota's corn and soybean crop is in fair, good, or excellent condition. This is a significantly higher percentage of favorable conditions than those found in other Corn Belt states.
[see: Agricultural Statistics Service Crop Progress and Condition | U. of M. Southwest Research & Outreach Center (Lamberton) Soil Moisture | U. of M. Southern Research & Outreach Center (Waseca)]
The potential for wildfires is currently rated by DNR Forestry as Very High in northern tier counties, High across much of the northern one-half of Minnesota and in southeastern Minnesota, and Moderate elsewhere in the state.
[see: Fire Danger Rating Map]

Future prospects:

The September precipitation outlook projects below-normal conditions throughout Minnesota. September precipitation normals range from near two inches in far western Minnesota to around three and one-half inches in eastern sections of the state.
[see: Climate Prediction Center 30-day Outlook | September Precipitation Normal Map]
The September temperature outlook is weighted towards above-normal conditions across the state. Normal September high temperatures are in the mid-70s to start the month, dropping to the low to mid-60s by month's end. Normal lows are in the mid-50s early in the month, falling to around 40 by late September.
[see: Climate Prediction Center 30-day Outlook | September Temperature Normal Map]
The 90-day precipitation outlook for September through November offers an equal likelihood of below-normal, near-normal, or above-normal conditions across Minnesota. The September through November temperature projection tilts strongly towards above-normal conditions statewide.
[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:

None

Notes from around the state:

None

Upcoming dates of note:

September 20: National Weather Service releases 30/90 day temperature and precipitation outlooks
November 8: 20th Annual Kuehnast Lecture

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.drought.unl.edu - National Drought Mitigation Center
http://www.rrbdin.org/rddss - Red River Basin Drought Decision Support System, International Water Institute
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://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://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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