HydroClim Minnesota - February 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 HAS HAPPENED
- January 2007 precipitation totals were below average across most of Minnesota. January precipitation was short of the historical normal by more than one half inch in many places. A few locations in the southern one quarter of Minnesota reported near normal, to above normal, precipitation for the month.
(see: http://climate.umn.edu/cawap/monsum/monsum.asp )
- monthly mean temperatures for January 2007 were warmer than average throughout Minnesota. Mean temperatures for the month ranged from five to eight degrees above normal. The first part of January was exceptionally warm. Temperatures in early January were 15 to 30 degrees above normal. High temperature records and warm low temperature records were tied or set on January 3rd, 4th, and 5th. Temperatures returned to typical January readings by mid-month and remained near, to below, normal for the remainder of the month. Extreme values for January ranged from 48 degrees at Winona on the 3rd, to -34 degrees at Embarrass on the 16th.
(see: http://climate.umn.edu/cawap/monsum/monsum.asp , http://climate.umn.edu/doc/journal/streak061209_070111.htm )
WHERE WE STAND NOW
- the snow depth map to be prepared on February 8 will show that much of Minnesota is covered by four to eight inches of snow. The greatest snow depths (eight to twelve inches) are reported in far northwestern Minnesota, locations in and near the Boundary Waters Canoe Area Wilderness, and along the southern two tiers of Minnesota counties. Snow depths are four inches or less across a large portion of central and north central Minnesota. With the exception of far southern counties, Minnesota's snow cover is significantly less than the historical median for the date. For many central and north central Minnesota counties, snow depths are near all-time lows for this time of year.
(see: http://climate.umn.edu/doc/snowmap.htm , http://climate.umn.edu/doc/journal/snowdrought0607.htm )
- dryness has been entrenched across northern and central Minnesota for nearly nine months. Nine-month precipitation totals have deviated negatively from historical averages by more than six inches across most of the northern one half of Minnesota.
(see: http://climate.umn.edu/doc/journal/drought_situation_report_2007.htm )
- the National Drought Mitigation Center (NDMC) - U. S. Drought Monitor to be released on February 8 will continue to indicate that most northern Minnesota counties remain in the "Extreme Drought" or "Severe Drought" categories. The northern reaches of the Red River Valley are depicted in the "Moderate Drought" or "Abnormally Dry" classification. The "Abnormally Dry" polygon covers much of central and southern Minnesota. The NDMC index is a blend of science and subjectivity where intensity categories are based on several indicators.
(see: http://www.drought.unl.edu/dm/monitor.html )
- stream discharge in northern Minnesota watersheds remains low. Mississippi River flow conditions are very low due to long-term precipitation deficits in the headwaters area.
(see: http://water.usgs.gov/cgi-bin/dailyMainW?state=mn&map_type=weekd )
- soil frost depths are generally between 18 and 36 inches. However, soils in areas where snow can be readily trapped (turfgrass surfaces, forests, and swamps) have less frost. Historically, soil frost reaches maximum depth in late February.
(see: http://climate.umn.edu/doc/observatory.htm , http://www.mvp-wc.usace.army.mil/projects/reservoirs.shtml )
- the seasonally cold temperatures in late January, and the bitterly cold temperatures in early February, increased lake ice thickness dramatically. Nonetheless, ice conditions continue to be unpredictable in some locations and caution is advised when venturing onto Minnesota's lakes.
- the February precipitation outlook from the Climate Prediction Center tilts significantly towards below normal conditions across Minnesota. Historically, February is Minnesota's driest month with precipitation normals ranging from near one half inch in northwestern Minnesota to just over one inch in far eastern sections of the state. The median snow depth at the end of February ranges from under 5 inches in southwest Minnesota to over 18 inches on the ground in northeastern Minnesota (greater than 30 inches in the Lake Superior highlands).
(see: http://www.cpc.ncep.noaa.gov/products/predictions/30day , http://climate.umn.edu/img/normals/precip/precip_norm_02.htm )
- the February temperature outlook leans towards above-normal conditions in western Minnesota counties. Elsewhere in Minnesota, the outlook indicates no significant tendencies away from climatological probabilities. Normal February high temperatures range from the low-teens in the north to near 20 in the south early in the month, climbing to the mid-20's to low 30's by month's end. Normal February low temperatures range from near minus 10 degrees in the far north to the single digits above zero in southern Minnesota early in the month; ascending to the low single digits in the north, mid-teens in the south by the end of February.
(see: http://www.cpc.ncep.noaa.gov/products/predictions/30day , http://climate.umn.edu/img/normals/temp_norm_adj/temp_norm_adj_02.htm )
- the 90-day precipitation outlook for February through April indicates no significant tendencies away from climatological probabilities across Minnesota. The February through April temperature outlook indicates a considerable tilt towards above-normal conditions throughout the state.
(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/ )
FROM THE AUTHOR
NOTES FROM AROUND THE STATE
- Northern Minnesota will face many lingering drought issues in 2007. In order to recover rapidly from the 2006 precipitation deficits, spring and summer rainfall totals will need to greatly exceed historical normals. This is possible, but not climatologically likely. The drought was quick to develop, but most likely its impacts will be slow to repair. In keeping with the dry pattern established in 2006, snowfall totals during winter of 2006-2007 have thus far been well short of average. Some drought concerns for the 2007 growing season include:
* antecedent dry conditions, along with a continuation of sparse winter snow cover, could lead to a significant increase in spring wildfire risk
* streams dropping below protected flow thresholds after the spring melt runoff
* low lake water levels and associated water access issues
* ground water levels lowering in lagged response to precipitation deficits. Ground water levels will also respond to increased pumping pressures.
* inadequate soil moisture conditions further impacting agriculture, especially forage crops
* inadequate soil moisture conditions further stressing forest communities, making them more vulnerable to pests
UPCOMING DATES OF NOTE
- February 15, National Weather Service releases 30/90 day temperature and precipitation outlooks
- February 22, Minnesota Drought Task Force meets
- on or before February 23, National Weather Service releases probabilistic outlooks for spring flooding
WEB SITES FEATURED IN THIS EDITION
http://climate.umn.edu - Minnesota Climatology Working Group
http://www.drought.unl.edu - National Drought Mitigation Center
http://water.usgs.gov/cgi-bin/dailyMainW?state=mn&map_type=weekd - U.S. Geological Survey
http://www.mvp-wc.usace.army.mil - US Army Corps of Engineers, St. Paul District
http://www.cpc.ncep.noaa.gov - Climate Prediction Center
http://www.crh.noaa.gov/ncrfc - National Weather Service North Central River Forecast Center - Chanhassen
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