|HydroClim Minnesota - March 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 totals for February 2003 were generally below normal across most of Minnesota. Monthly totals averaged around one half inch statewide, roughly one quarter inch below the historical norm. Only within a swath dissecting central Minnesota did precipitation totals top normal. An early February snowstorm dropped six to ten inches of snow along a 50 mile wide band either side of a line extending from Montevideo to Forest Lake. The roughly one half inch of moisture associated with this snow event was the most precipitation received in these areas since mid-October of 2002. WHERE WE STAND NOW
- February was generally a cold month, with brief intrusions of warmer weather during the first few days of the month, and again during the third week of the month. Extremes temperatures around the state ranged from -36 F at Tower on the 25th to 55 degrees F at Theilman (Wabasha County) on the 21st. Across Minnesota, monthly February temperatures finished two to seven degrees below normal.
- as of February 27, snow cover remained sparse south of a line from Moorhead to Duluth. In these areas, snow depths ranged from zero to four inches. Snow cover north of the Moorhead to Duluth transect exceeded four inches. Snow depths greater than eight inches were reported in the far northern tier of counties. The snow depth ranking map shows that snow cover was below the historical median for the date nearly everywhere in Minnesota, and snow depths across large areas of the state ranked below the 20th percentile for the date.
- as of February 25, the National Drought Mitigation Center - U. S. Drought Monitor indicates that much of Minnesota falls within the "D0 - Abnormally Dry" category. Counties in northeastern and north central Minnesota are judged to be in the "D1 - Drought Moderate" category. The NDMC index is a blend of science and subjectivity where intensity categories are based on six key indicators and numerous supplementary indicators.
- the March 1 Palmer Drought Severity Index map from the Climate Prediction Center places almost all of Minnesota in the "Near Normal" category. Only central Minnesota ("Unusual Moist Spell") falls outside of the "Normal" designation. The Palmer Drought Severity Index is used for assessing long-term meteorological conditions.
- soil surface layers across Minnesota are dry in response to the late autumn and winter precipitation deficits. Soil moisture values in the mid and lower layers are ample. The soil moisture profile will change very little until the soil thaws.
- the U.S. Geological Survey indicates that stream discharge values for Minnesota rivers (where winter reporting is possible) are at or below the normal category for the date. Discharge values for northeast Minnesota streams are low, ranking below the 25th percentile for the date.
- soil frost continued to deepen across Minnesota during February. Cold temperatures, combined with limited snow cover, caused soil frost to penetrate beyond 30 inches in depth beneath sod-covered surfaces. Anecdotal reports of 60 inch or deeper frost depths under bare soil or disturbed areas have been noted. For many locations, soil frost is at the deepest levels observed in more than a decade. The deeply frozen soil created problems with septic systems and other below-grade plumbing. Soil frost historically reaches maximum depth in late February.
- Minnesota's lakes and ponds are ice covered. Cold temperatures and sparse snow cover caused lake ice to continue to thicken during February. Ice damage to shoreline property due to "ice jacking" has been reported in some areas (see "FROM THE AUTHOR" below).
- the March precipitation outlook from the Climate Prediction Center shows a tendency towards below normal conditions in the northeastern one half of Minnesota, with no significant tendencies away from climatological probabilities elsewhere in the state. March precipitation normals range from near one inch in northwestern Minnesota to around two inches in southeastern counties. March is a transition month when cold, dry continental air masses are gradually replaced by warmer, moist air on a more frequent basis. This is demonstrated by the fact that March normal precipitation is 50 percent higher than February normal precipitation, the greatest percentage increase between any two successive months.
- the March temperature outlook indicates a strong bias towards above normal conditions throughout Minnesota. Normal March high temperatures climb from the mid to upper 20's early in the month to the low to mid 40's by month's end. Normal March lows begin the month in the single digits above zero in the far north and near 10 degrees in the south. By late March, normal lows are in the low to mid 20's.
- the 90-day precipitation outlook for March through May shows a tendency towards below normal conditions in the eastern one half of Minnesota, with no significant tendencies away from climatological probabilities elsewhere in Minnesota. The March though May temperature outlook 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.
- 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.
FROM THE AUTHOR
- property owners occasionally return to their cabins in the spring to discover that powerful natural forces have been at work over the winter. Limited snow cover, along with Minnesota’s famously cold temperatures, combined to produce shoreline-damaging ice activity this winter. Ice damage to shoreline property is caused by the "jacking action" of an ice sheet. As air temperatures drop, cracks form. These cracks develop from different contraction rates at the top and bottom of the ice sheet and because the edges of the ice are sometimes firmly attached to the shoreline. When water rises in these cracks and freezes, the ice sheet expands slightly. When rising air temperature warms the ice, the additional expansion exerts a tremendous thrust against the shore. The expanding ice sheet moves soil to create "ice ridges" (also know as ice pushes or ramparts) as high as five feet or more. Alternate warming and cooling of an ice sheet causes additional jacking action which has been known to nudge masonry bridge piers out of plumb, push houses off their foundations, and topple retaining walls.
NOTES FROM AROUND THE STATE
- noneUPCOMING DATES OF NOTE
- March 14, Probabilistic Flood Outlooks issued by National Weather ServiceWEB SITES FEATURED IN THIS EDITION
- March 20, Climate Prediction Center releases 30/90 day temperature and precipitation outlooks
- Minnesota Climatology Working Group
http://www.drought.unl.edu/ - National Drought Mitigation Center
http://www.cpc.ncep.noaa.gov - Climate Prediction Center
- U.S. Geological Survey, Minnesota
- U.S. Army Corps of Engineers, St. Paul District
- Minnesota DNR Enforcement
- National Weather Service, Central Region Headquarters
- Minnesota DNR Waters
- Russ Schultz, Supervisor - Lake Management Unit, DNR Waters - Brainerd
- Judy Boudreau, Surface Water Hydrologist, DNR Waters - St. Paul
- Tim Crocker, Area Hydrologist, DNR Waters - Little Falls
- Dr. Mark Seeley, Professor, University of Minnesota - St. Paul
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