HydroClim Minnesota - December 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 12/5/01


- November precipitation was well above average in southwestern, south central, west central, and central Minnesota. Precipitation totals in these areas were one and one half to three and one half inches above normal. Elsewhere, precipitation was near normal in northwestern and southeastern Minnesota, and somewhat above normal in north central, northeastern, and east central Minnesota. Precipitation was scarce during the first three weeks of November, then two large-scale events dropped significant amounts of precipitation on much of the state in the last eight days of the month. A slow moving storm system moved through the Midwest on the 23rd and 24th, drawing warm, moist air into Minnesota. The storm dropped one to three inches of rain over a broad area of Minnesota. Yet another major storm moved through the region only two days later on the 26th and 27th of the month. This storm left a blanket of wet, heavy snow across many Minnesota counties. Snowfall totals topped 24 inches in Kandiyohi county, and exceeded 12 inches in many southwestern and central Minnesota communities. Heavy winds associated with this major winter storm created Lake Superior waves that pounded Duluth's lakefront and led to some damage.
(see: http://climate.umn.edu/cawap/monsum/monsum.asp , http://climate.umn.edu/cawap/nwssum/011126.txt , http://climate.umn.edu/doc/journal/011127storm.html )
- November temperature averages finished 9 to 13 degrees above the historical mean across the state. It was Minnesota's warmest November on record. Nearly every community in Minnesota set a monthly temperature record. When compared with the long-term November mean, and the corresponding variation around that mean, the average November temperature for the Twin Cities was among the most extreme positive monthly temperature departures ever recorded.
(see: http://climate.umn.edu/cawap/monsum/monsum.asp , http://climate.umn.edu/doc/journal/warm1101.htm )


- the heavy late November rainfall and snowfall brought relief to areas affected by precipitation deficits established during the later part of the 2001 growing season. Growing season precipitation totals in southwestern, central, east central Minnesota counties were significantly below normal, and the lack of soil moisture reserves available for the 2002 growing season was a concern. However, because the considerable November precipitation fell before soil freeze-up, the soil moisture profile has been amply recharged. While the soil laid first claim to the November precipitation, water levels in surface hydrology systems such as lakes, rivers, and wetlands are rising in response to the rain and snow melt.
- the November 26-27 snow storm dropped heavy snow across much of central Minnesota. The November 29 snow depth map shows a swath of more than 12 inches of snow cover from Pipestone to Pine City. As seen in the companion snow depth ranking map, some counties were at or above all-time record snow depths for the date. Temperatures in the days that followed climbed well above normal, rapidly settling and melting the snow. The warm air temperatures, plus a warm soil surface, have diminished snow cover to near zero in many areas.
(see: http://climate.umn.edu/doc/snowmap.htm )
- as of November 27, the National Drought Mitigation Center shows Minnesota to be free of any drought designation. 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 December 1 Palmer Drought Severity Index (PDSI) from the Climate Prediction Center depicts all Minnesota counties in the "near normal" category. 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 )
- in their final report of the season, the Minnesota Agricultural Statistics Service reported that topsoil moisture as of November 9 was rated 6% surplus, 56% adequate, 32% short, and 6% very short. This survey was conducted before the heavy rains and snow of late November. Anecdotal reports indicate that late-November precipitation was very efficient in replenishing the still unfrozen soil moisture profile.
(see: http://www.nass.usda.gov/mn/cwmn.htm )
- the U.S. Geological Survey indicates that 95 percent of Minnesota's streams are in the normal or above normal categories for the date. 25 percent of Minnesota's stream gauging stations report stream discharge above the 90th percentile for this time of year. The highest stream flows (relative to historical data) are found in the Red River basin, scattered areas of northern Minnesota, and southeastern Minnesota.
(see: http://water.usgs.gov/cgi-bin/dailyMainW?state=mn&map_type=weekd )
- most soil temperatures in Minnesota continue to remain above freezing. The extraordinarily warm temperatures of November and the insulating effect of the late November snow have combined to delay soil freeze up. Similarly, the formation of lake ice has been delayed or slowed by this combination of factors. While some smaller and shallower lakes are thinly covered with ice, many larger Minnesota lakes remain ice-free.
(see: http://climate.umn.edu/cawap/soilpan/011202.txthttp://climate.umn.edu/doc/observatory.htm  )


- the December precipitation outlook from the Climate Prediction Center shows no significant tendencies away from climatological probabilities. December precipitation normals range from around one half inch in western Minnesota to just over one inch in eastern sections of the state. The median snow cover at the end of December ranges from over 10 inches on the ground in northeastern Minnesota (20 inches in the Lake Superior highlands), to under 5 inches in the southwest. The December temperature outlook also shows no significant tendencies away from climatological probabilities. Normal December high temperatures are in the mid to upper-20's to start the month, dropping to the near 20 by month's end. Normal lows are around 10 degrees early in the month, falling to near zero by late December.
(see: http://www.cpc.ncep.noaa.gov/products/predictions/multi_season/13_seasonal_outlooks/color/seasonal_forecast.html )
- the 90-day precipitation outlook for December through February shows no significant tendencies away from climatological probabilities. The December though February temperature outlook tilts towards below normal conditions. An important factor influencing winter weather in the Midwest is the state of sea surface temperatures in the equatorial Pacific (El Niņo and La Niņa). At this time, neither El Niņo nor La Niņa conditions are prevalent. Climatologist sometimes jokingly refer to this as a "La Nada" condition. During "La Nada", winter weather in the Midwest can be quite variable, alternating between cold and mild spells, with intermittent snowy and dry periods.
(see: http://www.cpc.ncep.noaa.gov/products/predictions/multi_season/13_seasonal_outlooks/color/seasonal_forecast.html )
- the National Weather Service 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 stream flow and soil moisture across a basin. The model is 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/ahps/index.html )


- none


- none


- December 13, Climate Prediction Center releases 30/90 day temperature and precipitation outlooks


http://climate.umn.edu - Minnesota Climatology Working Group
http://enso.unl.edu/ndmc/ - National Drought Mitigation Center
http://www.cpc.ncep.noaa.gov - Climate Prediction Center
http://www.nass.usda.gov/mn/ - Minnesota Agricultural Statistics Service
http://water.usgs.gov/cgi-bin/dailyMainW?state=mn&map_type=weekd - U.S. Geological Survey, Minnesota
http://www.crh.noaa.gov/ahps/index.html - National Weather Service - Central Region Headquarters


- Amy Loiselle, DNR Waters Hydrologist - Eveleth

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