A monthly electronic newsletter summarizing Minnesota's climate conditions and the resulting impact on water resources. Distributed on the first Thursday of each month.
State Climatology Office - DNR Division of Ecological and Water Resources, St. Paul
distributed: December 6, 2012
What happened in November 2012:
[see: November 2012 Climate Summary Table | November 2012 Monthly Precipitation Map | November 2012 Precipitation Departure from Normal Map]
[see: Late Season Tornadoes]
- November was another dry and warm month - keeping with a theme established throughout 2012. Nearly all observers reported below normal precipitation for the month of November, except for a few spots in northern Minnesota where some heavier snows pushed monthly precipitation totals above average. Some of the heavier November monthly snowfalls totals included International Falls with 9.2 inches, Duluth with 10.1 inches, Red Lake Falls with 14.0 inches, and Isabella with 17.0 inches.
- November average monthly temperatures in Minnesota ranged from near normal to as much as five degrees warmer than normal. The larger positive departures in temperatures were in the southern counties. Extremes for the month ranged from a low of -11 degrees at Fosston (Polk County) on the 26th, to a high of 75 degrees on the 10th at various southern Minnesota communities. A number of maximum temperature records were set on November 10 and 11, as well as numerous days during the week of Thanksgiving.
- The warmth on November 10 contributed to the formation of tornadoes, a rare occurrence in Minnesota in November. Tornadoes were reported at various locations around the Twin Cities. Only a handful of tornadoes have been observed in Minnesota in November in the past.
What happened in November 2012:
- The U. S. Drought Monitor, released on December 6, places portions of northwestern, west central, central, southwestern, and south central Minnesota in the Extreme Drought category. Most of the rest of Minnesota is deemed to be in Severe Drought. In total, 83% of Minnesota's landscape is in Extreme Drought or Severe Drought. This is double the land area reported in the Extreme Drought or Severe Drought categories at the start of November. 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 elsewhere in Minnesota developed rapidly due to very hot and very dry conditions that began in late-June and continued through the autumn. For large portions of Minnesota, July-through-November 2012 precipitation totals rank at or below the lowest on record. The U. S. Drought Monitor index is a blend of science and subjectivity where drought categories (Moderate, Severe, etc.) are based on several indicators.
- A few locations in the Lake Superior highlands of northeast Minnesota report four to six inches of snow cover as of this writing. Elsewhere in Minnesota, snow cover is sparse to nonexistent. In all locations, the present snow depth is below the historical median.
- The U.S. Geological Survey and Minnesota DNR report that stream discharge values are extremely low at numerous Minnesota reporting locations. Many stream flow values rank below the 10th percentile when compared with historical data for this time of year.
- Water levels on most Minnesota lakes are very low due to the dry summer and autumn. Lake Superior's water level is well below its historical average for this time of year.
- In their final report of the season (October 31), the Minnesota Agricultural Statistics Service reported that topsoil moisture was 27% Very Short, 42% Short, 29% Adequate, and 2% Surplus across Minnesota. Subsoil moisture is said to be 88% Very Short or Short. Soil moisture measurements made during November at University of Minnesota Research and Outreach Centers indicate extraordinarily dry conditions in the soil profile. Soil moisture content in the top five feet of soil at these locations is near all-time lows for this time of year. Ample early-spring rains are critically needed to replenish soil moisture reserves before the commencement of the 2013 growing season.
- Soil frost is either shallow or nonexistent in most Minnesota locales.
- Some Minnesota lakes and rivers are ice covered, especially in northern counties. However, many lakes have open water or are entirely free of ice. Lake and river ice is NEVER completely safe for walking or driving.
- The December precipitation outlook presents an equal likelihood of below-normal, near-normal, or above-normal conditions statewide. December precipitation normals range from around one-half inch in western Minnesota to over one and one-quarter inches in eastern sections of the state. The median snow cover at the end of December ranges from under five inches in southwest counties, to over 10 inches on the ground in northeast Minnesota (20 inches in the Lake Superior highlands).
- The December temperature outlook is weighted towards above-normal conditions in far southeastern Minnesota, equal chances of below-normal, near-normal, or above-normal conditions for the rest of the state. Normal December high temperatures are in the mid 20s to near 30 to start the month, dropping to the mid-teens to near 20 by month's end. Normal lows are around 10 degrees early in the month, falling to the mid-single digits above and below zero by late December.
- The 90-day precipitation outlook for December through February offers an equal likelihood of below-normal, near-normal, or above-normal conditions statewide. The December through February temperature projection tilts towards below-normal conditions across 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.
From the author:
- It is reasonable to assume that the present drought status will remain relatively unchanged throughout the winter. The historical average precipitation over the next three months is a meager two and one-half inches and the topsoil will soon be sealed by frost. Therefore, Minnesota will be highly dependent on abundant spring rains to ease the situation. Without abundant spring rains, a number of critical drought issues involving public water supply, agriculture, horticulture, tourism, and others will rapidly surface in the spring.
Contributions of information and suggestions are welcome!