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HydroClim Minnesota - August 2008

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 8/6/2008

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What happened in July:

• July 2008 precipitation totals were short of average by one to two inches in most locales. For a few locations, July rainfall amounts fell short of normal by two or more inches. Isolated heavy rain events permitted a handful of communities to match or exceed historical averages for the month, however a general pattern of dryness prevailed across Minnesota in July.
  [see: July 2008 Climate Summary Table]
• In spite of the persistent dryness across Minnesota in July, there were some episodes of severe weather and heavy rain, especially during an active seven-day period from July 10 through July 17.
  [see: Severe Weather: July 10  |  Severe Weather: July 10  |  Severe Weather: July 14  |  Severe Weather: July 16  |  Heavy Rains: July 16-17  |  Severe Weather: July 31]
• Monthly mean temperatures for July 2008 were very near historical averages. Extreme temperature values for July ranged from a high of 96 degrees on the 11th at Canby (Yellow Medicine County), to a low of 34 degrees at Embarrass (St. Louis County) on the 3rd and the 15th.
  [see: July 2008 Climate Summary Table]

Where we stand now:

• Much of Minnesota is in the midst of a mid-summer dry spell. For the seven-week period during the last two weeks of June and into early August, many Minnesota communities received less than three inches of rainfall. This came at a time of year when rainfall rates average roughly one inch per week. Thus, rainfall deficits over the seven-week dry spell topped three inches in many areas. Described another way, seven-week rainfall totals were less than 50 percent of normal for the period. Temperatures over the seven-week period were at, to slightly below, historical averages. This kept evaporative demand near seasonal norms and mitigated the situation somewhat. In 2007, late-June and early-July temperatures were well above average, amplifying evaporation and transpiration rates, and enhancing the drought situation.
  [see: Dry Mid-Summer 2008]
• Growing season precipitation totals to date (April 1 through early August) remain below average in northern sections of the Red River Valley, a small area of north central Minnesota, and a 40-mile wide band that bisects central Minnesota. In some small portions of northeastern and southeastern Minnesota, growing season rainfall totals are well above average, surpassing the 95th percentile (one year in twenty) when compared to other April-through-July totals in the historical record.
  [see: Weekly Precipitation Maps]
• The U. S. Drought Monitor, released on July 29, rated a large portion of central and southern Minnesota, and some counties in northern Minnesota as D0 - Abnormally Dry. A portion of Traverse County was placed in the D1 - Moderate Drought category. All other Minnesota locales are deemed to be free of drought conditions. 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 near the historical mid-range for the date across most of Minnesota. However, stream flows are trending downward, and in a few watersheds flow conditions have dropped below the 25th percentile for the date.
  [see: USGS Streamflow  |  DNR Streamflow]
• The Lake Superior water level is up 17 inches from last year at this time and climbing closer to the long-term average.
  [see: Corps of Engineers Great Lakes Water Levels]
• The Minnesota Agricultural Statistics Service reports that as of August 1, topsoil moisture was 8% "Very Short", 21% "Short", 68% "Adequate", and 3% "Surplus". Some of the driest topsoil conditions were found in central Minnesota and a small section of north central Minnesota. Fortunately, stored moisture lower in the soil profile supported crop conditions into early August. In the August 4 "Crop Progress and Condition Report", 72 percent of corn and 74 percent of soybeans were rated in good or excellent condition.
  [see: Ag. Statistics Service Crop Progress and Condition]
• The potential for wildfires is rated by DNR Forestry as "Moderate" in some sections of northeastern Minnesota, "Low" elsewhere.
  [see: Fire Danger Rating Map]

Future prospects:

• The August precipitation outlook projects a tilt towards above-normal rainfall in the southeastern one quarter of Minnesota. Elsewhere in Minnesota, the outlook offers equal chances of above, near, or below average conditions. 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 offers no significant tendencies away from climatological probabilities. Normal August high temperatures are around 80 degrees to start the month, dropping to the mid-70's by month's end. Normal lows are around 60 degrees early in the month, falling to the mid-50's by late August.
  [see: Climate Prediction Center 30-day Outlook  |  August Temperature Normal Map]
• The 90-day precipitation outlook for August through October indicates no significant tendencies away from climatological probabilities across most of Minnesota. The long-term precipitation outlook tilts towards above-normal conditions in extreme southwestern Minnesota. The August through October temperature projection offers equal chances of above, near, or below average conditions throughout most of the state. The temperature outlook leans towards above-normal conditions in Minnesota's Arrowhead region.
  [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 River Forecast Center]

From the author:

• None

Notes from around the state:

• None

Upcoming dates of note:

• August 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.crh.noaa.gov/mpx - National Weather Service Forecast Office, Chanhassen
• 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 - Detroit District, US Army Corps of Engineers
• 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 - Climate Prediction Center, National Weather Service
• http://www.crh.noaa.gov/ncrfc - North Central River Forecast Center, National Weather Service

Acknowledgements

• None

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Last modified: August 6, 2008