Drought Situation Report - July 21, 2006

More drought information resources are found at http://climate.umn.edu/doc/journal/dry_summer_2006.htm.

Recent rain brings some relief
Some welcome rain fell on July 19, 2006 focused primarily on south central and southeastern Minnesota. Martin and Faribault counties were among the drier places in the southern half of the state. The two to four inch rain in these counties was beneficial to agricultural interests. Another streak of heavier rain, roughly from Mankato to Rochester, fell upon an area that has been somewhat better off than the rest of southern Minnesota There was no significant widespread rain north of a line from Ortonville to Forest Lake.

Seasonal weather overview:
Dryness has been entrenched in Minnesota for nine weeks. Large-scale, precipitation-producing weather systems have been absent since mid-May. For much of this time, Minnesota has been under the influence of weak northwesterly flow in the upper atmosphere. During the summer, such a weather pattern leads to geographically-isolated and short-lived showers and thunderstorms, along with comfortable temperatures. During the past week, Minnesota joined much of the continental U.S. under an enormous dome of high pressure, continuing the dry weather and elevating temperatures. The timing of the dry weather has been most unfortunate. The period from late-May into mid-July is historically one of the wettest times of the year. 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, led to the rapid onset of drought. The precipitation shortfalls have led to deteriorating crop conditions, low stream flows, and increased wildfire danger.

Weather this past week:
Rainfall for the past week was plentiful in some areas of west central and southeastern Minnesota. However, the rain was not widespread and did little to alleviate Minnesota's rapidly developing drought conditions. Weekend temperatures reached the upper 90's in most locales. Saturday temperatures climbed to 100 degrees in some places. The extreme heat boosted evapotranspiration rates, baking an already parched landscape.

Drought Monitor Map

Drought status:
The latest National Drought Mitigation Center Drought Monitor released Thursday, July 20, places northwestern, central, and east central Minnesota in the "Severe Drought" category. All other Minnesota locations, with the exception of southern Minnesota, are depicted in the "Moderate Drought" classification. Southern Minnesota is depicted in the "Abnormally Dry" classification. Possible impacts for landscapes depicted as experiencing "Severe Drought" include: "Crop or pasture losses likely; water shortages common; water restrictions imposed". Possible impacts for landscapes depicted as experiencing "Moderate Drought" include: "some damage to crops, pastures; streams, reservoirs, or wells low, some water shortages developing or imminent; voluntary water-use restrictions requested". The next Drought Monitor will be released on Thursday, July 27. Without significant, wide-spread rain, many areas of Minnesota will either maintain or experience worsening drought conditions. The rains that fell across southern Minnesota on July 19th, will help the southern counties.

Sector briefs:
Agriculture - The Agricultural Statistics Service reports that topsoil moisture for 78% of Minnesota's landscape is now "Short" or "Very Short". This is a tremendous increase in areal extent from only a few weeks ago. Minnesota's corn crop is in the midst of its critical reproductive stages. Heat and moisture stress during this period leads to significant yield loss.
Stream flow - Stream flow in one half of Minnesota's rivers and streams falls below the 25th percentile when compared with historical data. Flow conditions in many northern and eastern Minnesota watersheds have dropped below the "Protected Flow" threshold (lowest 10th percentile), leading the Department of Natural Resources to suspend surface water appropriation permits in these areas.
Public water supply - Many Minnesota communities are imposing watering restrictions or outright watering bans.
Wildfire - Wildfire danger is "Very High" in northern and central Minnesota counties. The Cavity Lake Fire in the BWCA area of the Superior National Forest is reported at 28,500 acres as of July 21. This includes the total acres of land and water combined. Actual burned acres are about 22,000.

Nine-week precipitation totals, departure, and ranking:
Rainfall totals over the past nine weeks were less than four inches in many counties and less than two inches in some areas. Nine-week rainfall totals deviated negatively from historical averages by more than three inches in most areas. Rainfall deficits exceeded four inches in portions of northwest, central, and southeast Minnesota. When compared with other May 16 to July 17 rainfall totals in the historical database, this year's rainfall totals for the period rank among the lowest on record in some locales. The situation is especially acute in northwest Minnesota where near-record low precipitation totals are common across a multi-county area.

May 16 to July 17 2006 Precipitation Map May 16 to July 17 2006 Precipitation Departure Map y 16 to July 17 2006 Precipitation Ranking Map

More drought information resources are found at http://climate.umn.edu/doc/journal/dry_summer_2006.htm.

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URL: http://climate.umn.edu/doc/journal/drought_situation_report_2006_060721.htm
Last modified: July 21, 2006