Minnesota Drought Situation Report - September 27, 2007
Drought Monitor - September 25, 2007
The latest U. S. Drought Monitor(see map at right)
shows significant improvement from the previous week's map. Heavy
rains last week eliminated Extreme Drought designations in northeastern Minnesota
and substantially decreased the geographic extent of Extreme Drought areas in central Minnesota. Drought conditions across sizeable
sections of northern and central Minnesota improved by two categories; advancing from Severe Drought to
Abnormally Dry. Most of the Twin Cities metropolitan area is now free of any
drought designation. In spite of the improvement, lingering drought conditions continue across central and northern Minnesota.
Portions of Otter Tail, Wadena, Todd, Cass, Morrison, and Crow Wing counties remain in Extreme Drought.
The drought situation in the northern one third of 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, September 24 were quite heavy across large sections of northern and central Minnesota. Weekly rainfall
totals in excess of three inches were common (see map at left). Northwestern and southern Minnesota counties were missed by
the heavy rains. Long-term average rainfall rates rainfall totals are beginning to drop off at this time
of year to around one half inch per week.
Temperatures last week were warm, averaging four to six degrees above normal. Temperatures in some southern and western Minnesota
locations topped 90 degrees at least once last week.
Summer Dryness (June 5 - September 24):
Dryness was entrenched across northern and central Minnesota for much of the summer. September rains have significantly improved the situation in many areas. However, rainfall
for the sixteen-week period from June 5 through September 24 totaled less than eight inches for some locations in west central and central Minnesota
(see map below). In these areas, rainfall totals for the period were five or more inches short of the
historical average (see map below). When compared with historical rainfall totals for the same sixteen-week time frame, 2007 values ranked at
or below the 5th percentile (one year in twenty 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 21, topsoil moisture across roughly 20% Minnesota's landscape was "Short" or "Very Short". This is a significant
improvement from the previous week when one half of the state's topsoil was reported as deficient. The growing season has ended 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 in
about 10% of Minnesota's rivers and streams remains below the 25th percentile when compared with historical data for this time of year. At the beginning of
September, 33% of Minnesota's rivers and streams were experiencing low flow conditions. Flow conditions in a
few north central and northwestern Minnesota watersheds continue to rank below the 10th percentile for the date.
Lake levels -
Water levels are 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 somewhat in response to the September rains.
Lake Superior water level is expected to be at an all-time low
for September when the final monthly statistics are calculated.
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.