HydroClim Minnesota - October 2007

A monthly electronic newsletter summarizing Minnesota climate conditions and the resulting impact on water resources.

Distributed on the Wednesday following the first Monday of each month.

State Climatology Office - DNR Waters

compiled 10/3/2007


- September 2007 rainfall totals were well above historical averages in many Minnesota counties. Drought-stricken regions of central and northern Minnesota received welcome rains, improving the situation considerably. Monthly rainfall totals in excess of four inches were common in these areas, as well as in sections of southeastern Minnesota. In some counties, rainfall totals topped six inches for the month. For a few locations in Minnesota's Arrowhead region, monthly rainfall totals set new September records by exceeding ten inches. This is more than triple the historical average for the month. By contrast, September rainfall in some northwestern and southwestern counties fell short of the historical average by nearly two inches.
(see: http://climate.umn.edu/cawap/monsum/monsum.asp )
- on September 6, a strong weather system moving through the Midwest dropped over six inches of rain on portions of St. Louis, Lake, and Cook counties. Rainfall totals surpassed eight inches in central St. Louis County. The deluge led to overtopped and washed out sections of roads and highways. The situation was greatly tempered by the long-term drought conditions that existed prior to the rain event. A storm of this magnitude and intensity would have certainly had a greater impact had the landscape not been so dry. Another heavy rain event also affected portions of the Iron Range on September 18 when intense precipitation flooded Highway 169 near Grand Rapids.
(see: http://climate.umn.edu/doc/journal/flash_floods/ff070906.htm , http://climate.umn.edu/doc/journal/rain070918.htm )
- intense rains doused west central and central Minnesota on September 20 and 21. Three to five inches fell along an arc that bisected Minnesota from near Ortonville to Hinckley. The rain drenched portions of Stevens, Pope, Douglas, Todd, Stearns, and Morrison counties; an area that was suffering most intensely from the 2007 drought.
(see: http://climate.umn.edu/doc/journal/rain070920.htm )
- monthly mean temperatures for September 2007 were two to four degrees above the historical average in most locations. Extreme values for September ranged from a high of 97 degrees at Breckenridge (Wilken County) on the 3rd, to a low of 18 degrees at Embarrass (St. Louis County) on September 15. Three mid-month frosts effectively ended the growing season in most parts of the state. The most notable cold-snap occurred on September 15 when many Minnesota locations reported temperatures in the 20s. Some all-time low temperature records were set that morning.
(see: http://climate.umn.edu/cawap/monsum/monsum.asp , http://climate.umn.edu/weathertalk/070921.txt )


- growing season rainfall (April 1 - early October) was extraordinarily variable across time and space in 2007. In many locations, a very dry June and July was more than offset by very wet weather in August and September. Growing season rainfall totals vary from around 16 inches in some central Minnesota locations to over 40 inches in southeastern Minnesota counties. In the wetter areas, growing season rainfall topped the historical average by more than eight inches. In sharp contrast, rainfall deficits in a few central Minnesota communities were more than eight inches for the period. As a result, the growing season rainfall ranking map is a patchwork quilt depicting historically wet and historically dry polygons ... sometimes in close proximity of their climatic opposites.
(see: http://climate.umn.edu/doc/weekmap.asp )
- the U. S. Drought Monitor released on September 27 places portions of central and northern Minnesota in the "Severe Drought" category. Much of the rest of the northern one-half of Minnesota falls in the "Moderate Drought" or "Abnormally Dry" designation. Substantial September rains produced two-category improvements in drought designations across much of the northern two-thirds of the state. The U.S. Drought Monitor will be updated on October 4, and will likely depict continued drought improvement in many locales. Drought conditions are not improving in all areas of Minnesota. Late-summer and early-autumn dryness in northwestern Minnesota is a concern. Future U.S. Drought Monitor products will stay abreast of that developing situation. 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. The U. S. Drought Monitor index is a blend of science and subjectivity where intensity categories are based on several indicators.
(see: http://climate.umn.edu/doc/journal/drought_situation_report_2007_070927.htm , http://droughtmonitor.unl.edu/ )
- the U.S. Geological Survey reports that stream discharge values in only 7% of Minnesota's rivers and streams now rank below the 25th percentile when compared with historical data for this time of year. This is a substantial improvement from early September when stream flow in one third of the state's rivers and streams ranked in the lowest quartile. By contrast, roughly one third of the state's rivers and streams now report stream discharge that ranks in the highest 25th percentile historically.
(see: http://water.usgs.gov/cgi-bin/dailyMainW?state=mn&map_type=weekd , http://climate.umn.edu/dow/weekly_stream_flow/stream_flow_weekly.asp )
- water levels remain 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 in response to significant September rain. However, lakes are often the last hydrologic systems to show drought recovery. The Lake Superior water level was at an all-time record low monthly average for the month of August, and may also have set a September record. In spite of the September rains, further record low levels are possible in the coming months.
(see: http://www.glerl.noaa.gov/data/now/wlevels/levels.html , http://www.dnr.state.mn.us/lakefind/ )
- the Minnesota Agricultural Statistics Service reports that as of September 28, topsoil moisture across 17% 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.
(see: http://www.nass.usda.gov/Statistics_by_State/Minnesota/Publications/Crop_Progress_&_Condition/index.asp )
- the DNR Division of Forestry classifies current wildfire danger as "Low" across most of Minnesota. Wildfire danger in far northwestern Minnesota is categorized as "Moderate".
(see: http://www.dnr.state.mn.us/forestry/fire/ )


-  the October precipitation outlook from the Climate Prediction Center indicates no significant tendencies away from climatological probabilities across Minnesota. Normal October precipitation ranges from one and one half inches in northwestern Minnesota, to over two and one half inches in portions of north central and northeastern Minnesota.
, http://climate.umn.edu/img/normals/precip/precip_norm_10.htm )
- the October temperature outlook indicates no significant tendencies away from climatological probabilities across Minnesota. Normal October high temperatures fall from the low to mid 60's early in the month, to the upper 40's by month's end. Normal October low temperatures drop from the low 40's early in the month to near 30 by late-October.
(see: http://www.cpc.ncep.noaa.gov/products/predictions/30day , http://climate.umn.edu/img/normals/temp_norm_adj/temp_norm_adj_10.htm )
- the 90-day precipitation outlook for October through December indicates no significant tendencies away from climatological probabilities across Minnesota. The October through December temperature projection tilts towards above-normal conditions in all Minnesota counties.
(see: http://www.cpc.ncep.noaa.gov/products/predictions/90day/lead01/index.html )
- the National Weather Service produces long-range probabilistic river stage and discharge outlooks for the Red River, Minnesota River, and Mississippi River basins. These products are part of the National Weather Service's Advanced Hydrologic Prediction Service (AHPS).
(see: http://www.crh.noaa.gov/ncrfc/ )
- although drought conditions have improved greatly in the Upper Mississippi River basin, the National Weather Service continues to routinely produce low flow projections for the Mississippi River near Anoka and at St. Cloud.
(see: http://www.crh.noaa.gov/crnews/display_story.php?wfo=ncrfc&storyid=9487&source=0 )


- the Minnesota Drought Task Force continues to share information among the many entities monitoring and responding to the 2006-2007 drought situation. Facilitated by the DNR Division of Waters, this information sharing involves meetings, e-mail distributions, and Web postings.


- none


- October 18: National Weather Service releases 30/90 day temperature and precipitation outlooks
- October 18: 15th Annual Kuehnast Lecture  (see: http://climate.umn.edu/doc/journal/kuehnast_lecture )


http://climate.umn.edu - Minnesota Climatology Working Group, Minnesota DNR Waters and University of Minnesota Department of Soil, Water, and Climate
http://droughtmonitor.unl.edu/ - National Drought Mitigation Center
http://water.usgs.gov/cgi-bin/dailyMainW?state=mn&map_type=weekd - U.S. Geological Survey
http://www.dnr.state.mn.us/waters - Minnesota DNR Waters
http://www.nass.usda.gov - USDA, National Agricultural Statistics Service
http://www.dnr.state.mn.us/forestry - Minnesota DNR Forestry
http://www.cpc.ncep.noaa.gov - Climate Prediction Center, National Weather Service
http://www.crh.noaa.gov/ncrfc - North Central River Forecast Center - Chanhassen, National Weather Service


- none

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