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
WHAT HAPPENED IN
- 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.
- 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
- 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.
- 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.
WHERE WE STAND NOW
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.
- 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
- 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
- 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.
- 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.
- 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".
- 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.
- 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.
- 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.
- 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).
- 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.
NOTES FROM THE AUTHOR
- 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.
NOTES FROM AROUND THE STATE
UPCOMING DATES OF NOTE
- October 18: National
Weather Service releases 30/90 day temperature and precipitation
- October 18: 15th Annual Kuehnast Lecture (see:
WEB SITES FEATURED IN THIS EDITION
http://climate.umn.edu - Minnesota
Climatology Working Group, Minnesota DNR Waters and University of Minnesota
Department of Soil, Water, and Climate
http://www.drought.unl.edu - National
Drought Mitigation Center
- U.S. Geological Survey
- Minnesota DNR Waters
http://www.lre.usace.army.mil - Detroit District,
US Army Corps of Engineers
http://www.nass.usda.gov - USDA,
National Agricultural Statistics Service
- Minnesota DNR Forestry
Climate Prediction Center, National Weather Service
North Central River Forecast Center - Chanhassen, National Weather Service
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