Minnesota Drought Situation Report - October 4, 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 2, 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 in central Minnesota last week eliminated Extreme Drought designations
and substantially decreased the geographic extent of the Severe Drought polygon.
This week's drought monitor presents worsening drought conditions in northwestern Minnesota. The drought classification in the northern Red River
Valley was downgraded from Abnormally Dry to
The drought situation in north central and northeastern 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 worsening
situation in northwestern Minnesota is a reflection of very dry weather in late summer and early autumn 2007.
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 1 were moderate to heavy across all but northwestern Minnesota. Weekly rainfall
totals in excess of three inches were common in southeastern Minnesota (see map at left). One to three inch totals were
reported in many central Minnesota communities. Long-term average rainfall rates are now around one half inch per week.
Temperatures last week were warm, averaging four to six degrees above normal. Temperatures in nearly all Minnesota locations
climbed into the 80's at least once last week.
Summer Dryness (June 5 - October 1):
Dryness was entrenched across northern and central Minnesota for much of the summer. September rains significantly improved the situation in many areas. However, rainfall
for the seventeen-week period from June 5 through October 1 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 seventeen-week time frame, 2007 values ranked at
or below the 10th percentile (one year in ten occurrence) in some counties (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 September 28, topsoil moisture across 17% 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 7% 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 third 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 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 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 most of Minnesota. Wildfire danger in far northwestern
Minnesota is categorized as Moderate.
More drought information resources are found at http://climate.umn.edu/doc/journal/drought_information_resources.htm.
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Last modified: October 4, 2007