THE FARGO SNOWSTORM OF 6-8-JANUARY-1989

This paper documents the snowstorm that hit eastern North Dakota and w estern Minnesota during 6-8 January 1989. Fargo, North Dakota, set rec ords for both the greatest 24-h snowfall and the greatest single-storm snowfall with a total of 62 cm. Investigation of regional surface obs ervation time series showed that the snowfall occurred during the earl y stages of a cyclone event, but the entire snowfall ended before prim ary cyclogrenesis began. Instead, an arctic front, not directly associ ated with the incipient cyclone, was a focus for increasing frontogene sis 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 snowfal l. Snowfall ceased as the cold side of the sloping maximum reached the Fargo area. Small values of equivalent potential vorticity indicate t hat 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 quasigeostrop hic Row.