HydroClim Minnesota - April 2001

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 4/4/01


- March 2001 precipitation totals were about one inch below normal across most of Minnesota. March precipitation ranged from approximately one quarter inch in the north to roughly one inch in the south. Much of the March precipitation fell during a single storm that dropped six to 10 inches of wet, heavy snow on southern, central and northeastern Minnesota.
(see: http://climate.umn.edu/cawap/monsum/monsum.asp )

- March temperatures were near normal in the northern one third of Minnesota, but finished three to six degrees below normal elsewhere. Heavy winter snows and near to below normal March temperatures caused snow cover to persist into early April in most Minnesota counties.
(see: http://climate.umn.edu/cawap/monsum/monsum.asp )

- the 2000-2001 winter season brought significant snowfall to many Minnesota counties. 2000-2001 seasonal snowfall totals exceeding 60 inches were common throughout western and southern Minnesota. Snowfall totals in excess of 72 inches were reported in northeastern Minnesota. Snowfall totals in 2000-2001 ranked above the 80th percentile across much of southern, western, and northeastern Minnesota. In some communities, seasonal snowfall exceeded the 95th percentile. By contrast, snowfall in areas of far north central Minnesota fell well below the median. Average annual snowfall in the southern one half of Minnesota ranges from 36 inches in the west to around 50 inches in the east. 2000-2001 snowfall topped the historical average by approximately two feet in western Minnesota, and by more than 18 inches in many southern Minnesota counties.
(see: http://climate.umn.edu/doc/journal/flood_2001/snow00-01.htm )


- as of the end of March, many northern Minnesota communities continued to report more than eight inches of snow on the ground. However, much of the northern portion of the Red River valley was nearly free of snow. Snow cover in southern Minnesota is diminishing rapidly, but a significant amount of snow remains in drifted areas. The cold March temperatures delayed snow melt in many Minnesota counties. The March 29 ranking map showed that snow depths in the southern two thirds of Minnesota ranked above the 80th percentile for the date. For some areas of central and southern Minnesota, snow depths were above the 95th percentile.
(see: http://climate.umn.edu/doc/snowmap.htm )

- snow water equivalent data gathered by the National Weather Service showed that the snow pack across Minnesota generally contained two to four inches of water as of March 26. Some areas within the Minnesota River basin, and some locations in Minnesota's Arrowhead region, reported more than four of snow water equivalent. In spite of the relatively cool temperatures, March's high sun angle and long days worked to shrink and consolidate the snow pack. Snow densities vary across the state but are generally around 33% (approximately one inch of water for each three inches of snow cover). Snow at this density will readily give up its water when energy is introduced.
(see: http://www.crh.noaa.gov/ncrfc/html_frames/snowindex.html )

- soil frost depths across the state range from zero to 12 inches in areas receiving early and persistent snow cover, deeper in areas blown free of snow throughout the winter. Frozen soils are thawing from the bottom up and the top down. In many areas the top few inches of soil are experiencing a daily cycle of freezing and thawing. Some snow melt water is entering the topsoils.
(see: http://www.mvp-wc.usace.army.mil/bulletins/Snow_Ice_Frost.html )

- streams are beginning to rise in many locations ... in some cases rapidly. The U.S. Geological Survey indicates that stream flows at some southern Minnesota locations, including sites along the Minnesota River, now exceed the 90th percentile when compared to historical values for the date. Some flooding has begun in these areas, with more significant flooding expected within the next week. Stream flows reported by many gauging stations within the Red River basin are above the historical median as well. Minor flooding has been reported thus far in some areas within the basin. Significant flooding is forecast to occur along the upper Red River within the next five days.
(see: http://water.usgs.gov/cgi-bin/daily_flow?mn )

- all of Minnesota's lakes remain ice covered. On average, lake ice-out occurs during the first week of April in the southern tier of Minnesota counties; near the end of the second week of April in the Twin Cities metropolitan area; towards the end of the third week of April for Brainerd, Alexandria, Detroit Lakes area lakes; and during the final week of April in far northern Minnesota. Assuming near-normal April weather, this year's lake ice-out will be later than historical averages. A later than average ice-out is especially notable coming on the heels of record-breaking or near record-breaking early lake ice-outs in 2000.
(see: http://climate.umn.edu/doc/ice_out/ice_out_status_01.htm )

- as of their March 29 release, the National Drought Mitigation Center - "U.S. Drought Monitor" shows Minnesota to be free of any drought designations. The NDMC index is a blend of science and subjectivity where intensity categories are based on six key indicators and numerous supplementary indicators.
(see: http://enso.unl.edu/monitor/monitor.html )

- the March 31 Palmer Drought Severity Index (PDSI) depicts some of Minnesota as experiencing an "Unusual Moist Spell". Counties in southwestern, central, and northwestern Minnesota fall in this grouping. Counties in the rest of the state are categorized as "Near Normal". The Palmer Drought Severity Index is used for assessing long-term meteorological conditions.
(see: http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/regional_monitoring/palmer.gif )


- the 30-day outlook from the Climate Prediction Center shows no significant tendencies (equal chances of below, near, and above normal) in April precipitation for Minnesota. April precipitation normals range from an inch and a half in northwestern Minnesota to near three inches in the southeast. The April temperature outlook tilts towards below normal values. Normal April high temperatures are in the low to mid 40's early in the month, rising to near 60 by month's end. Normal April lows are near 30 to start the month and climb to around 40 as the month ends.
(see: http://www.cpc.ncep.noaa.gov/products/predictions/multi_season/13_seasonal_outlooks/color/seasonal_forecast.html )

- the 90-day precipitation outlook for April through June tilts towards above normal precipitation. The April through June temperature outlook calls shows no significant tendencies away from climatological probabilities.
(see: http://www.cpc.ncep.noaa.gov/products/predictions/multi_season/13_seasonal_outlooks/color/seasonal_forecast.html )

- the National Weather Service now produces long-range probabilistic river stage and discharge outlooks for the Red River and Minnesota River basins. A hydrologic model is initialized using the current conditions of the river, water equivalent of the snow cover, soil moisture, and soil temperature. The model is then allowed to run into the future with multiple scenarios using more than 30 years of climatological data. The climatological data are weighted by the 90 day outlooks for temperature and precipitation trends. The model output offers a complete range of probabilistic values of stream stage and discharge for numerous forecast points. The product offers a risk assessment tool which can be used in long-range planning decisions involving flooding or low-flow concerns. These products are part of the National Weather Service's Advanced Hydrologic Prediction Service (AHPS) and will be produced near the middle of each month. The AHPS service will be available for the Mississippi River Basin in the autumn of 2002.
(see: http://www.crh.noaa.gov/fgf/ahps/ahpsmain.htm for the Red River basin, http://www.crh.noaa.gov/mpx/ahps/index.html for the Minnesota River basin)


- the late-season snow cover has all but guaranteed spring snow-melt flooding this year in some areas. Those with interests in flood-prone areas should carefully monitor National Weather Service flood forecasts. National Weather Service offices with forecast responsibilities for Minnesota's rivers offer excellent Web sites which present the latest flood forecast information.
(see: http://www.dnr.state.mn.us/waters/climate/flood_2001/index.html )

- (repeated from February newsletter) the U.S. Geological Survey is testing a new Web site designed to offer water resources data for Minnesota (and other states). See: http://water.usgs.gov/mn/nwis . The USGS would appreciate comments from water resource professionals.


- from Dan Lais, DNR Waters Area Hydrologist - Stearns and Benton counties
(April 2) Most tributary streams and watercourses are open in the main channel with bank ice still present. Most ditches and storm sewers are open and conveying water. Frost depths vary. In some areas the frost is absent and groundwater recharge should be occurring. Lakes and wetlands remain ice covered with relatively good ice conditions yet for fishing. The snow pack appears depleted, with bare spots showing up in most crop fields. Snow pack conditions will likely change quickly with the warm weather predicted for this week. I have not received any reports of isolated flooding from runoff or stream flows. Hopefully this trend will continue.


- April 12, Climate Prediction Center releases 30/90 day temperature and precipitation outlooks


http://climate.umn.edu - Minnesota Climatology Working Group
http://www.crh.noaa.gov/ncrfc - National Weather Service - North Central River Forecast Center
http://enso.unl.edu/ndmc - National Drought Mitigation Center
http://www.cpc.ncep.noaa.gov - Climate Prediction Center
http://water.usgs.gov/cgi-bin/daily_flow?mn - U.S. Geological Survey, Minnesota
http://www.crh.noaa.gov/fgf - National Weather Service Forecast Office - Grand Forks
http://www.crh.noaa.gov/mpx - National Weather Service Forecast Office - Chanhassen
http://www.mvp-wc.usace.army.mil - U.S. Army Corps of Engineers, St. Paul District
http://water.usgs.gov/mn/nwis - U.S. Geological Survey - Water Resources for Minnesota test site


- Dan Lais, DNR Waters Hydrologist - Sauk Rapids
- Dana Dostert, DNR Waters Hydrologist - St. Paul

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