Heavy Snow in Iowa, January 9 to 10, 2009

Low pressure moved into Kansas and deepened during the afternoon of the 9th and moved east across northern Missouri during the night and morning hours of the 10th. A very strong temperature contrast became established along a frontal boundary extending through the low. Polar air was in place over northern Iowa and areas north with temperatures in the teens. In contrast, temperatures were in the low 50s over southern Iowa and in the 50s and 60s to the south of Iowa. Moisture streamed north into the system during the late afternoon and evening hours with surface dew point values reaching the 40s to low 50s south of the low. The airmass was dry initially, but was overcome by the evening hours. Very warm air did stream in aloft with 850 mb temperatures above +10 C. over southern Iowa during the early afternoon. This set the stage for a band of ice pellets and some freezing rain during the initial stages of the snow event. With the dry atmosphere, temperatures aloft cooled quickly and changed the ice pellets to snow fairly quickly. Other than the initial onset of the precipitation, most of the precipitation fell as snow. A band of moderate snow set up across central into east central Iowa as a strong deformation zone set up to the north of the low pressure track. A band of 6 to 8 inch snowfall occurred in a band about two counties wide between the Interstate 80 and U.S. Highway 30 corridors from just west of Interstate 35 east. Some of the heavier snowfall totals included 8.1 inches just southwest of Newton in Jasper County, 7.6 inches in Boone County in Boone, 7.5 inches in Marshall County at Marshalltown, 7.4 inches in Tama County at Garwin, 7.2 inches in Jasper County at Kellogg, and 7 inches just northeast of Des Moines in Polk County. Roadways became quite slippery, however the snow was generally of light consistency with little wind during the event. As a result, the heavy snowfall was more of an inconvenience rather than a life threatening event.