Minnesota Drought Situation Report - October 11, 2007
Announcement: Due to improving conditions, and a less drought-sensitive time of year, this situation report
will be updated monthly instead of weekly during the autumn and winter. The narrative will be prepared on the first Thursday of each month. The
document will be revised more frequently if notable changes in the drought situation occur.
Drought Monitor - October 9, 2007
The latest U. S. Drought Monitor (see map at right)
shows continued improvement in drought conditions for many Minnesota counties (view previous week's map).
Heavy rains across much of Minnesota last week eliminated the Severe Drought
designation in southern St. Louis and southern Lake counties, and substantially decreased the geographic extent of the
Moderate Drought polygons in central and northwestern Minnesota. The primary areas of concern at this time are pockets of Severe Drought
centered on Wadena and International Falls.
The drought situation in northern Minnesota is the result of a very dry 2006, a snow-sparse 2006-2007 winter, and
dry 2007 mid-summer weather. The drought situation in the central third of Minnesota is due to an extremely dry 2007 growing season
(see: 12-week U.S. Drought Monitor animation).
The U. S. Drought Monitor index is a blend of science and subjectivity where intensity categories are based on several indicators.
Last week's weather:
Rainfall totals for the week ending Monday morning, October 8 were moderate to heavy across much of the southeastern two-thirds of Minnesota. Weekly rainfall
totals in excess of two inches were common in these areas (see map at left). After Monday's map data deadline, an
additional one to two inches of rain fell in northwestern Minnesota on October 8.
Long-term average rainfall rates are now around
one half inch per week. Temperatures last week were very warm, averaging eight to twelve degrees above normal. Temperatures
in many Minnesota locations climbed into the 80's at least once last week.
Rainfall since early June:
Dryness was entrenched across northern and central Minnesota for much of the summer. September and early October rains significantly improved the situation in many areas.
However, rainfall for the eighteen-week period from June 5 through October 8 totaled less than ten inches for some locations in west central and central Minnesota
(see map below). In these areas, rainfall totals for the period were four or more inches short of the
historical average (see map below). When compared with historical rainfall totals for the same eighteen-week time frame, 2007 values ranked at
or below the 10th percentile (one year in ten occurrence) in some areas of west central Minnesota (see map below). The period from May through September is historically
the wettest time of the year in Minnesota. Long-term average rainfall rates during the heart of the summer are around one inch per week. Very dry weather, occurring during a
time of year when ample rain is typical, leads to the rapid intensification of drought. The lack of precipitation, along with very high evaporation rates, produced
deteriorating crop conditions, lower stream flows and lake levels, and increased wildfire danger.
Agriculture - The
Agricultural Statistics Service reports that as of October 5, topsoil moisture across 12% of Minnesota's landscape was "Short" or "Very Short". This is a substantial
improvement from the conditions reported in early August when nearly 85% of the state reported less than adequate soil moisture conditions. The growing season ended in
mid-September for Minnesota's row crops. Because the plants will not longer consume water, rainfall that occurs during the remainder of the autumn will be very effective at
replenishing the soil moisture profile. Fall 2007 rainfall will strongly influence the soil moisture status at the start of the 2008 growing season.
Stream flow - Stream discharge values in only a few of
Minnesota's rivers and streams now rank below the 25th percentile when compared with historical data for this time of year. This is a substantial improvement
from early September when stream flow in one third of the state's rivers and streams ranked in the lowest quartile. By contrast, stream discharge in roughly one half of the state's
rivers presently ranks in the highest 25th percentile historically.
Lake levels -
water levels remain low on many Minnesota lakes, exposing shoreline, and in some cases, making water access difficult. Anecdotal reports indicate that lake levels in
central and northern Minnesota have rebounded in response to significant September and October rain. However, lakes are often the last hydrologic systems to show drought recovery.
The Lake Superior water level was at an all-time record
low monthly average for the month of September. In spite of the September and October rains, further record low levels are possible in the coming months.
Wildfire Danger - The Department of Natural Resources - Division of Forestry classifies current
wildfire danger as Low across all of Minnesota.
More drought information resources are found at http://climate.umn.edu/doc/journal/drought_information_resources.htm.
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Last modified: October 11, 2007