Minnesota Drought Situation Report - July 17, 2007
Drought Monitor - July 10, 2007
The latest U. S. Drought Monitor 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 the southern one half of Minnesota. Most locations in this area received less than a quarter inch of rain
for the seven-day period ending Monday morning, July 16. Rainfall amounts topped one inch for the week in northwestern and north central Minnesota.
Monday rain occurring after the Monday morning map deadline ranged
from one half inch to one inch in portions of southern Minnesota. It was a seasonally cool week with temperatures averaging three to five degrees below average. Cooler temperatures
reduce evaporation rates and ease drought stress somewhat.
Seasonal weather overview:
Dryness has been entrenched across much of the southern two thirds of Minnesota for much of May, June, and into mid-July. The timing of the dry weather
has been 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 in June, has led to deteriorating crop conditions, low
stream flows and lake levels, and increased the danger of wildfire.
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. Growing season rainfall totals
have deviated negatively from historical averages by more than four inches across many east central, central, southwestern, and south central
Minnesota counties. Seasonal rainfall deficits exceeding five inches are reported along a band extending from the metropolitan area through Mankato and
southwestward into Fairmont. Spotty four-inch deficits are also reported in central Minnesota, and in southwestern Minnesota. When compared with other
seasonal rainfall totals to date in the historical database, this year's rainfall totals for the period rank below the 20th percentile
(one year in five) in the driest areas.
Agriculture - The
Agricultural Statistics Service reports that as of July 13, topsoil moisture for 68% of Minnesota's landscape was "Short" or "Very Short". This is a 10% increase
from the previous week. Corn and soybean conditions in many areas continue to decline in response to the diminishing soil moisture reserves.
Stream flow - Stream discharge in roughly
one third of Minnesota's rivers and streams is below the 25th percentile when compared with historical data for this time of year.
Flow conditions in some northeastern and east central
Minnesota watersheds are near the
protected flow threshold (lowest 10th percentile), leading the Department of Natural Resources to carefully monitor surface water appropriations
in these areas. Mississippi River flow conditions remain very low along all of the upper reaches of the river.
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 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. The wildfire danger is rated as Low
in southeastern counties.
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 17, 2007