Minnesota Drought Situation Report - September 13, 2007
Drought Monitor - September 11, 2007
The latest U. S. Drought Monitor (see map at right)
places portions of Minnesota's Arrowhead region and portions of central Minnesota in the Extreme Drought
category. Much of the rest of the northern two-thirds of Minnesota falls in the Severe Drought
or Moderate Drought designation. Most of northwestern Minnesota is described as being
Abnormally Dry. This week's Drought Monitor map includes two notable changes from the
previous week's map. Drought conditions in sections of northeastern Minnesota were improved by
one to two categories due to a heavy rain event on Thursday, September 6. By contrast, conditions continue to deteriorate in
west central Minnesota. A one-category decline in drought conditions is indicated for portions of Becker, Otter Tail, and Wadena counties.
The drought situation in the northern one third of Minnesota is the result of the lingering impacts 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 10 were quite large in northeastern Minnesota (see map at left). All,
or most, of Koochiching, Itasca, St. Louis, Lake, and Cook counties reported at least two inches of rain for the week. Five or more inch totals
were common in central St. Louis, northern Lake, and western Cook counties. In drought-stricken areas of west central Minnesota, rainfall totals for the week were
small, generally less than one quarter of an inch. Sections of already-soggy southeastern Minnesota received one to three inches of rain last week.
Temperatures last week were very warm,
averaging three to eight degrees above normal. Many locations reported at least one temperature of over 90 degrees.
Summer Dryness (June 5 - September 10):
Dryness has been entrenched across north central, northeastern, west central, and central Minnesota for much of the summer. Rainfall for the fourteen-week period from June 5
through September 10 totaled less than six inches for many locations in west central and central Minnesota (see map below).
In these areas, rainfall totals for the period were six or more inches short of the historical average (see map below).
When compared with historical rainfall totals for the same fourteen-week time frame, 2007 values ranked at or below the 5th percentile (one year in twenty occurrence)
for many counties (see map below). In a few areas, the June 5 - September 10 rainfall totals were near all-time record low values.
The period from May through September is historically the wettest time of the year in Minnesota. Long-term average rainfall rates during this time interval 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, led to deteriorating crop conditions, lower stream flows and lake levels, and increased wildfire danger.
Agriculture - The
Agricultural Statistics Service reports that as of September 7, topsoil moisture across nearly 40% 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. On August 7, a
federal agricultural disaster was declared for 24 Minnesota counties suffering from drought.
Farmers and ranchers in an additional 32 adjacent counties are also eligible for drought recovery assistance.
Stream flow - Stream discharge in
27% of Minnesota's rivers and streams remains below the 25th percentile when compared with historical data for this time of year.
Flow conditions in many north central, northeastern, central, and east central
Minnesota watersheds rank below the 10th percentile for the date. Mississippi River flow conditions remain very low along the upper reaches of the river.
Mississippi River discharge near Anoka is at roughly the same flow rate as it was during the 2006 drought, but above the all-time record
low for the date set in 1934. National Weather Service projections
indicate that flow in Mississippi through the Twin Cities may drop to near-historic low levels by mid-October.
Lake levels -
Water levels are very low on many Minnesota lakes, exposing shoreline, and in some cases, making water access difficult. Anecdotal reports indicate that many lakes in northern,
west central, central, and east central Minnesota are a foot or more below average levels for the date. The
Lake Superior water level is expected to be at an all-time low
for September when the final statistics are calculated.
Wildfire Danger - The Department of Natural Resources - Division of Forestry classifies current
wildfire danger as Low to Moderate across Minnesota.
More drought information resources are found at http://climate.umn.edu/doc/journal/drought_information_resources.htm.
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Last modified: September 13, 2007