Winter Storm in Iowa, January 6 to 7, 2010

The third winter storm in a months time struck Iowa on the 6th and 7th. A cold airmass was in place over the central U.S. as a strong upper level trough approached from the northwest. The trough intensified as it moved into Iowa with the 500 mb low pressure area closing off over the state. There was a weak reflection at the surface however. During the first part of the storm, all that was noted at the surface was an inverted trough of low pressure. As the storm gained strength, a weak circulation developed over Iowa, and then moved eastward slowly with the upper low. Snow began over western Iowa on the morning of the 6th and spread east very slowly as the precipitation fought the dry air to the east. By late afternoon, snow was falling over all of Iowa. The snow was light and fluffy in nature, with snow ratios in the 20:1 to 30:1 range. For the most part, accumulations were gradual, generally a half inch or less per hour, however the snow continued for an extended period of time. Heavy snowfall occurred over the northwest part of the DMX CWA with reports of 8 inches of snow west of the Estherville Airport in Emmet County, and also in Pocahontas County at Pocahontas. Seven inch amounts were reported in the Fort Dodge area of Webster County, in Boone County south of Boone, and also Hancock County at Kanawha. The main problem with this system was not the snow amounts however. The fresh fluffy snow fell on a deep snowpack already present across the state. Due to previous storms, many of the ditches had already drifted over, setting the stage for much more blowing and drifting than would normally be expected. As the surface low exited the area, strong northwest winds overspread the state with speeds in the 25 to 35 MPH range, with gusts to near 45 MPH at times. The winds picked up the light snow and caused considerable blowing and drifting of the snow. Whiteout conditions were reported at times across much of the state and travel became hazardous. Many of the state's schools were closed due to the storm on the 6th, with a large percentage remaining closed on the 7th as roads in many areas drifted shut and became impassible. Snow crews were taken off of the roads in many locations as it became too dangerous to clear the roads due to poor visibility and the fact that the roads drifted shut nearly as fast as the crews could clear them. Accidents were too numerous to mention and driving was not recommended across most of the state on the 7th. Numerous major roads were closed by drifts of 6 feet in height or more. Reports indicated that along U.S. Highway 20, drifts were up to 8 feet high and three blocks long, completely closing the highway. Winds diminished to 15 to 25 MPH during the evening of the 7th, however cold temperatures combined with the winds to produce wind chill indices in the 20 to 40 below zero range.