1999-10-28_AgendaPacket - Laserfiche WebLink

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Page 10 A,1" L ~C Summer 1999 State Climatology Office DNR Waters The winter of 1998-1999 followed an autumn of mild temperatures and well-placed precipitation patterns. Figure 1 shows above normal September through November precipitation in northeastern Minnesota. This region experienced a very dry growing season, therefore, the additional precipitation brought welcome relief. Conversely, much needed dry weather benefitted southeastern Minnesota, an area where the growing season had been quite damp. Temperatures in the autumn continued ayear-long trend of warmth. The statewide average temperature was two to four degrees above normal in October and November. Above normal temperatures in November came even though a period of cold weather followed a massive storm on November 10th. This storm brought heavy snow, damaging winds and arecord-breaking low pressure to many locations. The weather soon modified and late November was extraordinarily warm. The warmth continued into early December. Minnesota was 15 to 20 degrees above normal for the first two weeks of the month. Many locations broke all- time high temperature records. The mild weather permitted outdoor activity not typically seen during a Minnesota December. Warm temperatures in November and. early December resulted in a delay of lake freeze- up across the state. Historical records of "ice-in" dates are sketchy, however, it appears that many lakes experienced their latest permanent "ice-in" date of the century. Another interesting hydrologic impact of this balmy weather was unusually high December stream flows in many rivers. December precipitation was very light, but the mild temperatures allowed. water in small tributaries to contribute flow to the larger sys- tems. Typically these smaller streams and ditches are ice-bound in early December. Arctic air finally reached Minnesota by mid- December, dropping temperatures below the average. The landscape, free of snow, was exposed to the arctic blast. This caused the soil to freeze rapidly. continued on page 11...