HydroClim Minnesota - July 2012
A monthly electronic newsletter summarizing Minnesota's climate conditions and the resulting impact on water resources. Distributed on the first Monday of each month.
State Climatology Office - DNR Division of Ecological and Water Resources, St. Paul
distributed: July 3, 2012
What happened in June 2012:
- June 2012 monthly precipitation totals created a hodgepodge of very wet and very dry conditions across Minnesota. Due to two exceptional rainfall events, extremely large monthly rainfall totals were reported in portions of northeastern and southeastern Minnesota. Monthly rainfall totals in these areas exceeded 10 inches, more than doubling the historical average. By contrast, rainfall totals across much of Minnesota, especially the southern two tiers of Minnesota counties and some sections of northwestern and north central Minnesota, were short of the historical average by one to four inches.
- Two intense rainfall events led to destructive flooding in June. Heavy thunderstorms on June 14 dropped rainfall totals of six to eight inches on portions of Rice, Dakota, and Goodhue Counties. The axis of the heaviest rainfall totals aligned nearly perfectly with the axis of the Cannon River watershed, amplifying the river flooding. On June 19 and 20, a large area of northeastern Minnesota received six to ten inches of rain over a 24-hour period. The rains, falling upon a landscape already saturated from previous rains, triggered major floods in Aitkin, Carlton, and St. Louis counties. Preliminary damage estimates for public infrastructure alone top 100 million dollars. In terms of rainfall intensity and the geographic extent of the heaviest of the rains, the event ranks among the worst in Minnesota's post-settlement history.
- Monthly mean temperatures for June 2012 were two to four degrees above average over most of Minnesota. It was Minnesota's ninth consecutive month of above-normal temperatures. Extreme temperature values for June ranged from a high of 99 degrees F at Amboy (Blue Earth County) and St. James (Watonwan County) on the 27th, to a low of 28 degrees F at Brimson (St. Louis County) on the 1st. The completion of the July 2011-June 2012 heating season marked the lowest number of seasonal heating degree days (a climatological measure of heating demand) in the 141 year Twin Cities climate record.
Where we stand now:
- The 2012 growing season has been extraordinarily wet across sections of central, east central, and northeast Minnesota. Seasonal precipitation totals starting with April 1 exceed 16 inches in many of these areas, topping the historical average by eight or more inches. By contrast, growing season rainfall for most of northwestern Minnesota has been short of average by two or more inches.
- The U. S. Drought Monitor, released on June 28, places some northwest Minnesota counties in the Moderate Drought category. Roughly one-quarter of the state is rated in the Abnormally Dry category. This week's excessive heat and recent precipitation shortages will likely lead to an expansion of Abnormally Dry areas in the next release. Nonetheless, the most recent release shows substantial improvement in the drought situation when compared with early May when 60 percent of Minnesota was said to be in the Moderate Drought or Severe Drought categories. 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 and Minnesota DNR report that stream discharge values are very low at some northwest Minnesota reporting locations. Stream flow values rank below the 10th percentile for this time of year in some of these watersheds. Stream flows are very high in many east central and northeastern Minnesota basins. Stream discharge values in these watersheds rank above the 90th percentile when compared with historical data for the date.
- Water levels on Minnesota lakes located within areas receiving the season's heaviest rainfalls continued to be very high. Lake Superior water level rose notably in June in response to heavy rains in the eastern portion of the basin.
- In their July 1 report, the Minnesota Agricultural Statistics Service reported that topsoil moisture is 3% Very Short, 19% Short, 69% Adequate, and 9% Surplus across Minnesota. This represents a degradation in conditions when compared with an early-June soil moisture survey reporting only 5% of the landscape Short or Very Short. However, 70 to 80 percent of Minnesota's corn and soybean crop is said to be in good or excellent condition. This is a significantly higher percentage of favorable conditions than those reported by other Corn Belt states.
- The potential for wildfires is currently rated by DNR Forestry as Very High in far northwest Minnesota. For some counties in northern Minnesota, wildfire potential is considered High or Moderate. The wildfire potential is considered Low in most of northeastern Minnesota and all of southern Minnesota.
- The July precipitation outlook projects equal chances of above-normal, near-normal, and below-normal conditions throughout Minnesota. July precipitation normals range from just over three inches in far northwestern Minnesota to over four inches in eastern sections of the state.
- The July temperature outlook is weighted towards above-normal conditions across the state. Normal July high temperatures are in the low to mid-80s. Normal July lows are around 60 degrees. July is historically the warmest month of the year in Minnesota.
- The 90-day precipitation outlook for July through September offers an equal likelihood of below-normal, near-normal, or above-normal conditions across the state. The July through September temperature projection tilts towards above-normal conditions in southern Minnesota, an equal likelihood of below-normal, near-normal, or above-normal conditions in northern Minnesota.
- 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.
Contributions of information and suggestions are welcome!
Last modified: June 26, 2015