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 5/8/02

WHAT HAS HAPPENED

- April precipitation totals varied widely across Minnesota. April precipitation totals were somewhat below normal in northern and western Minnesota, falling short of the historical average by approximately one half inch. Precipitation totals in central, east central, and southeastern counties finished the month above the average by more than one half inch. April's precipitation fell in many forms. Winter-like storms dropped snow on April 1, April 21, and April 27. Both the Twin Cities and St. Cloud reported their second snowiest Aprils on record. Thunderstorms on April 16, April 18, and April 24 produced damaging wind, hail and heavy rain.
(see: http://climate.umn.edu/cawap/monsum/monsum.asp , http://climate.umn.edu/doc/journal/snowstorm020401.htm , http://climate.umn.edu/doc/journal/snowstorm020421.htm , http://climate.umn.edu/doc/journal/snowstorm020427.htm )
- April monthly temperatures were near to somewhat below normal statewide. However, the monthly means hide the extraordinary variability observed within the month. Early April temperatures were 10 to 15 degrees below normal. By mid-April the temperatures warmed markedly, rising above historical averages by more than 20 degrees. Much of the southern two thirds of Minnesota topped 80 degrees on April 15, and many maximum temperature records were broken on that day. The Twin Cities reached 91 degrees, the earliest 90 degree temperature ever recorded in the spring in the metropolitan area. Temperatures cooled during the latter half of the month, again dropping below the norm by more than 10 degrees. On April 26, the observer at Embarrass (St. Louis county) reported a minimum temperature of 8 degrees, a new all-time state record low for the date.
(see: http://climate.umn.edu/cawap/monsum/monsum.asp , http://climate.umn.edu/doc/journal/mid-april2002heat.htm )


WHERE WE STAND NOW

- growing season precipitation totals to date (April 1 - May 6) offer a mosaic of differing conditions across Minnesota. Precipitation totals in central, east central, and southeastern Minnesota are above normal for the season, and rank above the 85th percentile. In portions of north central and northeastern Minnesota, growing season precipitation totals to date are less than half of normal, falling below the 20th percentile when compared with historical data for the period. In most other areas, growing season precipitation totals are near the median. 
(see: http://climate.umn.edu/doc/weekmap.asp )
- as of April 30, the National Drought Mitigation Center designates far northwestern Minnesota as undergoing a "Moderate Drought". The western two tiers of counties bordering North and South Dakota are classified as "Abnormally Dry". The remainder of the state is 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://www.drought.unl.edu/dm/monitor.html )
- the May 4 Palmer Drought Severity Index (PDSI) from the Climate Prediction Center places northwestern Minnesota counties in the "Moderate Drought" category. Other areas 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 Minnesota Agricultural Statistics Service reports on May 5 that the state's topsoil moisture was 14% surplus, 83% adequate, 3% short, and 0% very short. Quantitative soil moisture measurements are rare. However, recent measurements from University of Minnesota research locations in southern Minnesota indicate that soil moisture values in those areas are above average. Ground preparation and spring planting operations are keeping pace with historical averages in southern Minnesota; but cool weather is delaying work in northern sections of the state.
(see: http://www.nass.usda.gov/mn/cwmn.htm , http://swroc.coafes.umn.edu/Weather/Charts/Soil/2002/02_soil_water.html , http://climate.umn.edu/img/soil_moisture/wassm12.gif )
- the U.S. Geological Survey indicates that streamflows in many north central and northeastern Minnesota rivers are low, falling below the 25th percentile when compared with historical data for the date. Discharge values for the remainder of Minnesota streams are near to above historical medians for the date. 
(see: http://water.usgs.gov/cgi-bin/dailyMainW?state=mn&map_type=weekd, http://climate.umn.edu/dow/weekly_stream_flow/stream_flow_weekly.asp )
- nearly all of Minnesota's lakes are now free of ice. Some larger lakes along the Canadian border remain partially ice-covered. The extraordinarily warm weather during December, January, and February led to relatively thin and unconsolidated lake ice cover. It appeared certain that lake ice-out would arrive early this spring. However, cold March temperatures delayed ice-out progress. In the final result, lake ice-out dates were quite close to historical averages. 
(see: http://climate.umn.edu/doc/ice_out/ice_out_status_02.htm )
- the potential for wildfires is rated as moderate in many counties in the northern one half of Minnesota. The fire danger rating for all other areas is low.
(see: http://www.dnr.state.mn.us/forestry/fire/ )


FUTURE PROSPECTS

- the May precipitation outlook from the Climate Prediction Center shows no significant tendencies away from climatological probabilities. May precipitation normals range from two and one half inches in northwestern Minnesota to around four inches in southeastern counties. 
- the May temperature outlook also shows no significant tendencies away from climatological probabilities. Normal May high temperatures are near 60 early in the month, rising to the low to mid-70's at month's end. Normal May lows are near 40 to start the month and climb to around 50 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 May through July shows no significant tendencies away from climatological probabilities. The May though July temperature outlook also 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 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 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 are produced near the middle of each month. 
(see: http://www.crh.noaa.gov/ahps/index.html )


FROM THE AUTHOR

(repeated from last month)
- in the coming months you may hear a great deal about the onset of an "El Niño". The El Niño phenomenon is a semi-regular (every two to seven years) warming of the sea surface in the eastern equatorial Pacific Ocean. There are no known connections between El Niño and Minnesota's growing season weather. However, El Niños are often associated with warm and relatively snow free winters in Minnesota. I would like to emphasize that El Niño is not presently in place, but indications are that it may evolve later in the year.


NOTES FROM AROUND THE STATE

- none


UPCOMING DATES OF NOTE

- May 16, Climate Prediction Center releases 30/90 day temperature and precipitation outlooks 


WEB SITES FEATURED IN THIS EDITION

http://climate.umn.edu - Minnesota Climatology Working Group
http://www.drought.unl.edu/ - National Drought Mitigation Center
http://www.cpc.ncep.noaa.gov - Climate Prediction Center
http://www.nass.usda.gov/mn/cwmn.htm - Minnesota Agricultural Statistics Service
http://water.usgs.gov/cgi-bin/dailyMainW?state=mn&map_type=weekd - U.S. Geological Survey, Minnesota
http://www.dnr.state.mn.us/waters/programs/surwat_section/stream_hydro/productsf.html - Minnesota DNR Waters
http://www.dnr.state.mn.us/forestry/fire/ - Minnesota DNR Forestry
http://www.crh.noaa.gov/ahps/index.html - National Weather Service - Central Region Headquarters


ACKNOWLEDGEMENTS

Contributions of information and suggestions are welcome!