Heavy Snow in Iowa, January 4 to 6, 2005

The seasons first major winter storm hit Iowa from late in the afternoon of the 4th into the predawn hours of the 6th. The storm was a long and drawn out storm with a series of short waves lifting northeast across the area in a broad southwest flow aloft. Deep moisture was available for the system with a tropical connection in place. The main mechanism for the precipitation was isentropic lift. During the early stages of the storm a considerable amount of warm air was drawn in over cool polar air at the surface. The result was a mixture of freezing rain, ice pellets, and snow over the southeast third of the CWA during the first 6 to 12 hours of the event. Much of the snow fell in two rounds, though snowfall occurred during the entire period. The first came during the late evening of the 4th and early morning of the 5th and layed down a swath of several inches of new snow. The second round came as low pressure formed along a stationary front to the south of Iowa. Initially, the snow was the result of the warm air advection ahead of the low, then the deformation snow fell in the wake of the low. The heaviest snow fell during the evening of the 5th, with another several inches of new snowfall. The heaviest snow amounts fell from west central Iowa, from around Audubon, east through Ames, to near Waterloo.In this band, snowfall amounts in the 10 to 18 inch range were common. Some of the heavier snowfall included 17.5 inches in Bremer County at Denver, 16.5 inches northeast of Ames in Story County, 16 inches in Bremer County at Frederika, 15 inches in Roland in Story County, and 14.6 inches in Polk County at Johnston. To the south of the heavy snow band, icing was a common problem. Much of Iowa south of Interstate 80 received at least some icing with one tenth of an inch or more common. Over the south two tiers of Iowa Counties, one quarter to as much as three quarters of an inch of ice accumulated before the freezing rain changed to snow. Travel was hazardous across the state with many roads snow blocked and the Iowa D.O.T. recommending no travel. Nearly every school district in the CWA cancelled classes on the 5th and numerous other activities were cancelled or postponed. Winds during the storm were generally in the 20 to 25 MPH range with some higher gusts to around 35 MPH. There were reports of some blowing snow in open areas and considerable drifting occurred at all locations.