The Fargo Snowstorm of 6–8 January 1989

Abstract

This paper documents the snowstorm that hit eastern North Dakota and western Minnesota during 6?8 January 1989. Fargo, North Dakota, set records for both the greatest 24-h snowfall and the greatest single-storm snowfall with a total of 62 cm. Investigation of regional surface observation time series showed that the snowfall occurred during the early stages of a cyclone event, but the entire snowfall ended before primary cyclogenesis began. Instead, an arctic front, not directly associated with the incipient cyclone, was a focus for increasing frontogenesis and ascent over the Dakotas and Minnesota during the event. Upper-level two-dimensional frontogenesis calculations identified a sloping maximum in the lower troposphere associated with an 850-mb wave, which progressed through North Dakota during the period of heaviest snowfall. Snowfall ceased as the cold side of the sloping maximum reached the Fargo area. Small values of equivalent potential vorticity indicate that weak conditional symmetric stability existed, possibly helping the organization of the snowfall in a narrow band. This study points out the gross deficiencies in our knowledge of Northern Plains snowstorms and calls attention to the pitfalls of analyses based on quasigeostrophic flow.