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HydroClim Minnesota - October 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 10/8/2008

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What happened in September:

• September 2008 precipitation totals fell short of average by one to three inches in the southern one-third of Minnesota. By contrast, heavy rainfalls in some sections of the northern one-half of Minnesota caused monthly rainfall totals to exceed the long-term average by two or more inches. Unfortunately, the bulk of the rainfall missed many of Minnesota's drought-stricken areas. One opportune exception was the four or more inches of September rainfall reported in northwestern Crow Wing, eastern Cass, and southwestern Itasca counties where drought conditions were among the worst found in Minnesota.
  [see: September 2008 Climate Summary Table | Radar-based September Precipitation Estimate]
• Monthly mean temperatures for September 2008 were one to three degrees above historical averages. Extreme temperature values for September ranged from a high of 92 degrees on the 1st at several locations, to a low of 24 degrees at Embarrass (St. Louis County) on the 16th. As was the case throughout the summer, maximum temperatures above 90 degrees were not common. Frosts occurred in several northern counties during September, but the remainder of Minnesota escaped the month without frost, a factor that helped crops reach maturity.
  [see: September 2008 Climate Summary Table]

Where we stand now:

• Much of Minnesota remains impacted by a long-term dry spell. For the sixteen-week period beginning in mid-June and extending into early October, many Minnesota communities received less than eight inches of rainfall. This came at a time of year when rainfall rates average roughly one inch per week. Thus, rainfall deficits over the sixteen-week dry spell topped five inches in many areas. Described another way, sixteen-week rainfall totals were less than 60 percent of normal for the period. Temperatures over the sixteen-week period were very close to historical averages. This held evaporative demand near seasonal norms and mitigated the situation somewhat.
  [see: Drought 2008]
• Growing season precipitation totals to date (April 1 through early October) are significantly below normal in many counties in the southern one-third of the state, and a small portion of north central Minnesota. Conversely, in some portions of west central, east central, 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-September totals in the historical record.
  [see: Weekly Precipitation Maps]
• The U. S. Drought Monitor, released on October 2, classified large sections of Minnesota in the D0 - Abnormally Dry category or worse. Significant portions of the state were placed in the D1 - Moderate Drought classification. 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 highly variable across the state. Some Minnesota streams have flows that are below the 25th percentile in the historical distribution for early October. By contrast, the Red River and many of its tributaries report above-median flows in response to heavy rains that fell in August and September.
  [see: USGS Streamflow  |  DNR Streamflow]
• The Lake Superior water level is up 11 inches from last year at this time. However, dry late-summer/early-autumn weather in the basin has caused the water level to drop notably during the last two months. Levels on inland lakes in Minnesota's drought areas are low. In some cases, water levels are similar to those observed during the droughts of 2006 and 2007.
  [see: Corps of Engineers Great Lakes Water Levels]
• The Minnesota Agricultural Statistics Service reports that as of October 3, topsoil moisture was 7% "Very Short", 22% "Short", 66% "Adequate", and 5% "Surplus". Subsoil moisture was significantly consumed during the 2008 growing season. Autumn rains can lead to significant recharge in the soil moisture profile. Autumn rainfalls are often wide-spread and of low intensity. Autumn plant water use drops to near zero. Any rains before soil freeze-up will improve the subsoil moisture situation.
  [see: Ag. Statistics Service Crop Progress and Condition]
• The potential for wildfires is rated by DNR Forestry as "Moderate" along Minnesota's North Shore. Elsewhere across the state, the fire danger rating is "Low".
  [see: Fire Danger Rating Map]

Future prospects:

• The October precipitation outlook offers equal chances of above, near, or below average conditions. 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 no significant tendencies away from climatological probabilities across Minnesota. Normal October high temperatures fall from the low to mid 60's early in the month, to the upper 40's by month's end. Normal October low temperatures drop from the low 40's 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 indicates no significant tendencies away from climatological probabilities across Minnesota. The October through December temperature projection tilts towards above-normal conditions across the state.
  [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:

• October 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 - 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: October 8, 2008