Minnesota Drought Situation Report - July 24, 2007
Drought Monitor - July 17, 2007
The latest U. S. Drought Monitor (see map at right) places portions of north central, northeastern,
east central, central, south central, and southwestern Minnesota in the Moderate Drought category.
Most of the Lake Superior watershed, including an area of northeastern Minnesota, is classified as experiencing a
Severe Drought. Much of the remainder of the eastern three quarters of
Minnesota is depicted as being Abnormally Dry. The drought situation in the northern
one third of Minnesota is the result of the lingering impacts of a very dry 2006, and a snow-sparse 2006-2007 winter. The drought situation
in the southern two thirds of Minnesota is due to a dry 2007 growing season. 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:
Precipitation last week was generally light across Minnesota (see map below). Most locations in the state received less than a quarter inch of rain
for the seven-day period ending Monday morning, July 23. Significant rainfall was reported in just a few areas. Many locations along the southern tier of Minnesota
counties received one to two inches of rain for the week. Heavier rainfall totals were also reported to the south and east of Bemidji, in portions of southern
St. Louis County, and along a narrow band through the heart of the Twin Cities metropolitan area. Weekly temperatures were near
the long-term mean last week. Historically, the last two weeks of July and the first week of August are the warmest of the summer.
Seasonal weather overview:
Dryness has been entrenched across much of the southern two thirds of Minnesota for much of May, June, and July. The timing of the dry weather
is unfortunate. 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 during a warm June, has led to deteriorating crop conditions, lower
stream flows and lake levels, and increased wildfire danger.
Seasonal precipitation totals, departure, and ranking:
Rainfall totals since April 1 are less than eight inches across much of the southern one half of Minnesota (see map below). Growing season rainfall totals
have deviated negatively from historical averages by more than four inches across many central, east central, southwestern, and south central
Minnesota counties (see map below). This is roughly the equivalent of missing all of June's rainfall. Seasonal rainfall deficits exceeding five inches are
reported along a band extending from the metropolitan area through Mankato and
southwestward into Fairmont. Five-inch deficits are also reported in central Minnesota, and in portions of southwestern Minnesota. When compared with other
seasonal rainfall totals-to-date in the historical database, this year's rainfall totals for the season rank below the 20th percentile
(one year in five) across much of southern Minnesota (see map below).
Agriculture - The
Agricultural Statistics Service reports that as of July 20, topsoil moisture across nearly 75% of Minnesota's landscape was "Short" or "Very Short". Corn and soybean
conditions in many areas continue to decline in response to the diminishing soil moisture reserves. Only 40% of Minnesota's corn acreage is rated as "Good" or "Excellent".
Stream flow - Stream discharge in roughly
40% of Minnesota's rivers and streams is below the 25th percentile when compared with historical data for this time of year.
Flow conditions in many northeastern, central, and east central
Minnesota watersheds fall 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 heart of the 2006 drought.
Lake levels -
Lake levels continue to drop throughout Minnesota, exposing shoreline, and in some cases, making water access difficult.
Quantitative lake level data are difficult to obtain in real time. However, anecdotal reports indicate that many lakes, especially in central and east central Minnesota, are a foot or more average
levels for the date. Lake Superior water levels are
near all-time lows for the date and could fall below all-time seasonal lows by early autumn.
Wildfire Danger - Wildfire
danger is Moderate or High across most of Minnesota.
Public water supply - Many Minnesota communities
have imposed watering restrictions due to increased lawn watering demands.
More drought information resources are found at http://climate.umn.edu/doc/journal/drought_information_resources.htm.
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Last modified: July 24, 2007