|HydroClim Minnesota - March 2004
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
- February 2004 precipitation totals were near to above normal in most Minnesota communities. Only in sections of northwestern and north central Minnesota did precipitation fall short of the historical average. For the first time since June 2003, the monthly state-averaged precipitation total was above normal. While the abundant February snowfall was of great benefit to the winter recreation industry, its impact on Minnesota's hydrologic systems was modest.
- the most significant snow event of the month occurred during a multi-day period from January 31 through February 3 in southern and eastern Minnesota counties. Snowfall totals topped 10 inches in many south central and southeastern Minnesota communities. Another substantial snow event came on February 8, when a winter storm dropped a narrow six to ten inch band of snow from Appleton in west central Minnesota to Duluth.
- February 2004 mean monthly temperatures were near to slightly above normal across Minnesota. Temperatures during the first half the month were near to below normal. However, the later half of February was seasonally warm, with daily temperature climbing 10 to 15 degrees above normal. February extremes ranged from a high of 56 degrees at Canby of Yellow Medicine county on February 18, to a low of -44 degrees at Embarrass of St. Louis county on February 15.
WHERE WE STAND NOW
- tomorrow's (March 4, 2004) snow depth map will indicate that the southern one of half of Minnesota is covered by less than four inches of snow. The snow cover is nearly gone in many of these areas. More than eight inches of snow remains on the ground north of a line from Grand Forks to Duluth. Twelve or more inches of snow covers in ground in the far northern tier of counties, and snow depths of around 24 inches are reported in the Lake Superior highlands.
- a March 1 survey conducted by the National Weather Service indicates that the snow pack contains a modest liquid equivalent. Snow water equivalent values range from near zero in the snow-sparse areas of southern Minnesota, to around two and one half inches in the north. Snow water equivalent values of four to five inches are required for spring snowmelt flooding to become a concern.
- as of February 24, the National Drought Mitigation Center - U. S. Drought Monitor indicated that most of Minnesota was judged to be in the "D0 - Abnormally Dry" or "D1 - Moderate Drought" categories. Southeastern and south central Minnesota counties, and a small area of north central Minnesota, were rated in the "D2 - Severe Drought" classification. The NDMC index is a blend of science and subjectivity where intensity categories are based on six key indicators and numerous supplementary indicators.
- the soil profile remains dry across Minnesota due to late summer and autumn precipitation deficits. Soil moisture is notably short in the second and third foot beneath the surface. The soil moisture profile will change very little until the soil thaws.
- except for heavily wooded areas where soil frost is limited, Minnesota's soils are frozen to a depth of 18 to 36 inches. Historically, soil frost reaches its maximum depth in late February. On average, all layers of the soil profile are thawed by late March to early April in the south, early April to mid-April in the north.
- the March precipitation outlook from the Climate Prediction Center shows no significant tendencies away from climatological probabilities. Normal March precipitation ranges from near three quarters of one inch in northwestern Minnesota to nearly two inches in southern sections of the state. 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 also indicates no significant tendencies away from climatological probabilities. Normal March high temperatures climb from the 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 mid-teens in the south. By late March, normal lows are in the low 20's in the north, near 30 in the south.
- the 90-day precipitation outlook for March through May shows no significant tendencies away from climatological probabilities. The March though May temperature outlook indicates no significant tendencies away from climatological probabilities, except for far western Minnesota where a tilt towards below normal temperatures is indicated.
- the National Weather Service produces long-range probabilistic river stage and discharge outlooks for the Red River, Minnesota River, and Mississippi River basins. The latest model output indicates very low probabilities of significant river flooding between now and mid-April anywhere in Minnesota. The hydrologic model is initialized using current conditions of stream flow and soil moisture across a basin. The model is allowed to run into the future with multiple scenarios using multiple 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
- the chances for spring snowmelt flooding on Minnesota's rivers remains low. Unless conditions change substantially, flooding will not be an issue in the early spring. Of greater concern is Minnesota's ongoing precipitation shortfall. Substantial spring rains are required to refill depleted soil moisture reserves, and replenish surface water systems.
NOTES FROM AROUND THE STATE
UPCOMING DATES OF NOTE
- March 11, Spring Snowmelt Flood Outlook - NWS North Central River Forecast CenterWEB SITES FEATURED IN THIS EDITION
- March 18, 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://www.drought.unl.edu/ - National Drought Mitigation Center
- U.S. Army Corps of Engineers
http://www.cpc.ncep.noaa.gov - Climate Prediction Center
http://www.crh.noaa.gov/ahps - National Weather Service, Central Region Headquarters
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