HydroClim Minnesota: October 2011

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 Division of Ecological and Water Resources, St. Paul
prepared: October 5, 2011

What happened in September 2011:

• September 2011 was an exceptionally dry month across Minnesota. This marked the second consecutive month of widespread rainfall shortfalls. For many locations, September rainfall totals failed to reach one inch. In nearly all counties, monthly precipitation fell short of the historical average by one and one-half to two and one-half inches. In numerous locales, it was the driest September in the modern record.
• Monthly mean temperatures for September 2011 were close to the historical average for most Minnesota communities. Extreme temperature values for September ranged from a high of 94 degrees F at numerous southern Minnesota locations on the 1st, to a low of 19 degrees F at International Fall's (Koochiching County), Embarrass (St. Louis County), and Wannaska (Roseau County) on the 15th. Widespread below-freezing temperatures on September 15 and 16 ended the 2011 growing season in many Minnesota locales. In many communities, all-time low temperature records were set for those dates. In central and southern Minnesota, below-freezing temperatures in mid-September are rare, coming two to three weeks earlier than the historical median first-freeze date.

Where we stand now:

• Significant rainfall shortfalls have been reported across Minnesota over the past two and one-half months. Precipitation totals for the past ten weeks are less than two inches in many southern Minnesota counties, a negative departure from the long-term ten-week average of four to six inches. When compared with the same ten-week period in the historical database, the 2011 precipitation totals rank among the lowest on record.
• The U. S. Drought Monitor, released on September 29, depicts many counties in both southern and northern Minnesota as experiencing drought conditions. Portions of St. Louis, Lake, and Cook counties are said to be undergoing Severe Drought or Moderate Drought. Stream flow and lake levels in those areas are very low due to the lingering impact of precipitation deficits accrued during the 2010 growing season and spotty rainfall this season. The Drought Monitor places a large portion of south central and southwest Minnesota in the Moderate Drought category. The U. S. Drought Monitor index is a blend of science and subjectivity where drought categories (Moderate, Severe, etc) are based on several indicators.
• The U.S. Geological Survey reports that stream discharge values remain high in some western and central Minnesota watersheds, the lingering impact of a wet autumn 2010 and spring 2011. Conversely, stream flow measurements on many northern Minnesota rivers, and a few southern Minnesota rivers, rank below the 25th percentile when compared with historical data for the date. In St. Louis and Lake counties, for the Crow Wing River in north central Minnesota, and for the Le Sueur River in south central Minnesota, stream flow values rank below the 5th percentile for this time of year.
• The Lake Superior water level is the same as last year's elevation at this date, but down 13 inches from the long-term seasonal average. The water level on White Bear Lake (Ramsey/Washington county border) remains quite low. The White Bear Lake elevation is up by over one foot after reaching an all-time record low level mark in November 2010. Lake levels in western Cook, northern Lake, and northern St. Louis counties are very low when compared with historical averages for this time of year.
• As of October 2, the Minnesota Agricultural Statistics Service reported that topsoil moisture was 19% Very Short, 35% Short, 46% Adequate, and 0% Surplus. Topsoil moisture steadily declined through the months of August and September especially in southern Minnesota. The soybean harvest is progressing rapidly.
• The potential for wildfires is currently rated by DNR Forestry as Very High or High across all of Minnesota.

Future prospects:

• The October precipitation outlook shows a strong bias towards above-normal conditions over all of Minnesota. 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.
• The October temperature outlook tilts towards above-normal conditions across 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.
• The 90-day precipitation outlook for October through December no significant tendencies away from historical climatological probabilities anywhere in Minnesota. Likewise, the October through December temperature projection offers an equal likelihood of below-normal, near-normal, or above-normal conditions.
• 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).

From the author:

• Congratulations to State Climatologist, Jim Zandlo, who retired after 31 years of service to the State of Minnesota!