2002 Annual

Monday, 14 January 2002
The Atmospheric Phenomena of a mid-fall Blizzard
Jennifer L. Hanson, Univ. of North Dakota, Grand Forks, ND; and F. G. Martin, M. R. Estrem, D. L. Jacklitch, A. D. Kleinsasser, and J. E. Randall
During the evening of 23 October 2001, most models indicated a one to three inch snowfall event for the Northern Plains. By 4:20 a.m. the following morning, the National Weather Service (NWS) issued a snow advisory for a five county region centered around Grand Forks, ND, in anticipation of a three to five inch snowfall. With continued heavy snow and northwesterly winds sustained at 35 miles per hour, the NWS upgraded to a 15 county blizzard warning at 8:55 a.m. By early afternoon snowfall accumulation had exceeded 10 inches. Along with school and business closings, approximately 400 vehicles were stranded over a 10-mile stretch of Interstate 29 south of Grand Forks.

The models and local forecasts did not anticipate this blizzard. We attempt to resolve aspects that lead to both the storm and the missed forecasts. These aspects include how the storm developed (from both synoptic and mesoscale perspectives), why models and forecasters, both individually and collectively, were not able to properly forecast the blizzard, and developmental storm signatures that might be used for early identification of similar conditions.

Storm development progressed as follows. Initially, in a state of zonal, a "lead low" with weak upper level dynamics tracked east-southeast from British Columbia. While skirting along the U.S.-Manitoba border, this system pulled moisture northward into the tri-state region of North Dakota, South Dakota, and Minnesota. A trailing surface low, following a similar, but more southerly path, ran headlong into this pool of moisture. Fueled by this moisture, the trailing system strengthened considerably in the upper levels. The trailing surface low then slowly from approximately the Aberdeen, SD area into the arrowhead region of Minnesota. During this period the trailing system produced heavy snow and, through the attendant intense surface pressure gradient across North Dakota, strong surface winds. Meanwhile, a significant tongue of low- to mid-level moisture extending into the lower peninsula of Michigan was pulled to the weak lead surface low positioned north of Lake Superior. The lead surface low rapidly intensified with the help of both this moisture and the coupling of the upper level dynamics with the trailing low. During this intensification of the lead system the trailing surface low became uncouple and subsequently dissipated in the arrowhead region. As the trailing low weakened and the lead low strengthened, the snow dissipated across the area while strong winds remained. Later, the now coupled lead low continued to produce strong winds with little or no precipitation in Eastern North Dakota.

We plan to further resolve these aspects of this storm by looking at the storm's synoptic framework as well as its mesoscale details. Furthermore, model projections and forecasts will be analyzed and compared to actual events. Finally, some socioeconomic impacts of this storm on the area will be summarized.

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