|HydroClim Minnesota - April 2003
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
- precipitation amounts in March 2003 varied widely across Minnesota. Precipitation fell short of normal by more than one inch in west central, central, and southwestern Minnesota. March precipitation totals were somewhat above normal in portions of far northwestern, south central, and southeastern Minnesota. In many areas, precipitation deficits amplified a dry pattern that began in mid-October 2002. WHERE WE STAND NOW
- the period, November 2002 through March 2003, is among the driest five-month periods in Minnesota’s climate history. November 2002 through March 2003 precipitation totals were under two inches for large areas of Minnesota, and under four inches for almost the entire state. When compared with all other November through March periods in the historical data base, November 2002 through March 2003 precipitation ranks below the 25th percentile nearly everywhere, below the 5th percentile in many areas, and below the 1st percentile in a number of west central, north central, and northeastern Minnesota counties. A ranking below the 1st percentile indicates that a location was near or below the all-time minimum record for November through March precipitation.
- two significant precipitation events of note occurred in March 2003. A snowstorm on March 7 and 8 left a four to six inch swath of snow from southwest Minnesota into east central Minnesota. On March 27 and 28 a spring storm drifted through Minnesota, dropping more than an inch of rain in some southeastern Minnesota counties, and more than a foot of snow in north central and northeast Minnesota. An April 7 storm deposited more than eight inches of snow on the far southern tier of Minnesota counties.
- March temperatures were near to somewhat below normal across Minnesota. Very cold temperatures early in the month were offset by mild temperatures in mid-March. Low temperature records were set in some Minnesota communities on March 2, and March 5 through 9. Cold temperatures led to near complete ice cover on Lake Superior in early March. The last time Lake Superior substantially froze over was the winter of 1996-1997. Conversely, record setting high temperatures were reported in many Minnesota communities on March 14 through 17, and March 24. Extreme temperatures for March ranged from -39 degrees F at Tower to 77 degrees F at Jackson.
- Minnesota is nearly free of snow cover at this time. Some snow lingers in the southern tier of counties in the aftermath of this week's late season snowstorm. Some snow also remains in wooded areas of north central and northeastern Minnesota.
- as of April 8, the National Drought Mitigation Center - U. S. Drought Monitor indicates that much of the northern two thirds of Minnesota is judged to be in the "D1 - Drought Moderate" category. Other areas of Minnesota fall within the "D0 - Abnormally Dry" classification. The NDMC index is a blend of science and subjectivity where intensity categories are based on six key indicators and numerous supplementary indicators.
- soil surface layers in many areas across Minnesota are dry due to late autumn and winter precipitation deficits. Soil moisture in the middle and lower portions of the rooting zone is ample in some counties because of the considerable 2002 growing season precipitation.
- the U.S. Geological Survey indicates that stream discharge values for Minnesota rivers are at or below the normal category for the date. Stream flow in one half of Minnesota's rivers and streams are below the 25th percentile for the date, and 15 percent of the state's streams are below the 10th percentile. Minnesota's rivers and streams are typically at high levels at this time of year due to snow melt runoff. The lack of a substantial late winter snow pack significantly reduced runoff volumes, and thus has led to below average stream discharge.
- frost depths this past winter reached their deepest levels in more than a decade. Soil frost is thawing from both above and below at this time. This process leaves a mid-profile ice lens to thaw last. The depth and thickness of this mid-profile lens of ice varies widely across Minnesota.
(see: http://climate.umn.edu/doc/observatory.htm , http://www.mvp-wc.usace.army.mil/projects/reservoirs.shtml
- lakes in the southern one third of Minnesota are now free of ice. Smaller lakes in central Minnesota are also ice free. 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.
- the potential for wildfires is rated by DNR Forestry as moderate in the northwestern one quarter of Minnesota and some central and east central counties. The fire danger rating for all other areas is low.
- the April precipitation outlook from the Climate Prediction Center shows no significant tendencies away from climatological probabilities. April precipitation normals range from one and one half inches in northwestern Minnesota to around three inches in southeastern counties.
- the April temperature outlook also indicates no significant tendencies away from climatological probabilities. 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.
- the 90-day precipitation outlook for April through June shows no significant tendencies away from climatological probabilities. The April though June temperature outlook also indicates no significant tendencies away from climatological probabilities.
- the National Weather Service produces long-range probabilistic river stage and discharge outlooks for the Red River, Minnesota River, and upper Mississippi 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 historical climatological data. The climatological data are weighted by 90-day climate outlooks for temperature and precipitation trends. Model output offers a complete range of probabilistic values of stream stage and discharge for numerous forecast points. The product provides 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 are produced near the middle of each month.
FROM THE AUTHOR
NOTES FROM AROUND THE STATE
- noneUPCOMING DATES OF NOTE
- April 17, Climate Prediction Center releases 30/90 day temperature and precipitation outlooksWEB SITES FEATURED IN THIS EDITION
- Minnesota Climatology Working Group
http://www.drought.unl.edu/ - National Drought Mitigation Center
http://mrcc.sws.uiuc.edu/ - Midwestern
Regional Climate Center
- U.S. Geological Survey, Minnesota
- Minnesota DNR Division of Waters
- U.S. Army Corps of Engineers, St. Paul District
- Minnesota DNR Division of Forestry
http://www.cpc.ncep.noaa.gov - Climate Prediction Center
- National Weather Service, Central Region Headquarters
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