February 23-25, 2007 Ice Storm

 

A widespread and crippling ice and snow storm affected eastern Iowa, northwest and western Illinois, and extreme northeast Missouri in late February 2007Low pressure developing in the central Plains, spread a swath of freezing rain, snow and sleet across northeast Iowa and extreme northwest Illinois during the evening of February 23, 2007.  This storm system would then develop into a major ice storm the next day on February 24, 2007.

Ice accumulations of around one inch were common, with some reports to near two inches! To make matters worse, east winds gusting over 50 mph, combined with the heavy ice accumulation, brought down numerous tree branches and power lines, along with several thousand power poles. There were even whole trees crashing down from the weight of the ice. Widespread power outages occurred, affecting over 180,000 people, which lasted more than a week in some of the rural areas. Many shelters were opened to accommodate those without power. Widespread tree and power line damage was reported across much of the northeast two thirds of Iowa.  Reports of 345 KV transmission lines down were received from Tama and Black Hawk Counties in Iowa.  During this time, easterly winds were blowing in the 20 to 40 MPH range, exacerbating the problem.  Tama County reported 75 miles of power lines down.  Butler County Iowa reported at least 250 power poles snapped already by the evening of the 24th. At the height of the storm, at least 265,000 customers were without power.  Interstate Power and Light Company reported that 1000 miles of transmission line was down at one point and 2000 utility poles were snapped in their area covered by Alliant Energy.  MidAmerica Energy reported 360 miles of transmission line down and 1600 utility poles snapped in their area.  Final statewide damage figures for the three utility entities involved in the ice storm were $70,000,000 damage to Alliant Energy equipment, $36,000,000 damage to MidAmerica Energy equipment, and $32,000,000 damage to Rural Electric Cooperative equipment.  The freezing rain changed over to sleet, and eventually snow late on the 24th into the 25th.

In the northern portions of the region in the colder air, snow was the problem. Accumulations of up to 7 inches occurred, with strong winds combining to create blizzard conditions. There was one direct death and one indirect serious injury due to the ice storm in northwest Illinois.  Six to twelve inches of snow was common across much of Iowa northwest of a Bedford, to Des Moines, to Grundy Center line. Some of the heavier amounts include 11.5 inches at Algona in Kossuth County, and 10 inches at Dana in Greene County and Estherville in Emmet County. Along with the snow, many areas reported occasional visibility near zero in blowing snow on the night of the 24th into the 25th. Travel became very hazardous with many roads closed due to the combination of snow, blowing snow, fallen wires, and fallen trees. Numerous activities were canceled on the 25th as well. By the afternoon of the 25th, Iowa Governor Chet Culver had already given 60 counties the state disaster declaration by the afternoon following the storm. Subsequently, 46 of the counties, mostly in northeast Iowa, received a Presidential Disaster Declaration. Some of the hardest hit areas were in Poweshiek, Marshall, Tama, and Black Hawk Counties. Costs in the city of Waterloo, for example, were over $2,000,000 during the first week after the storm.

This winter storm went into the books as one of the worst winter storms in many years. Although ice storms are not documented all that well, this storm appears to be the worst ice storm in Iowa in the past 40 years due to the large areal extent of the storm. Farther to the south and west the precipitation fell as rain. Enough rain fell to cause some minor flooding on the Chariton and Middle Rivers. The Middle River crested about a foot over flood state in Indianola, while the Chariton River crested a little over 2 feet over flood stage in Chariton.

Technical Note:

A major winter storm affected Iowa through the 24th and 25th of February.  A powerful upper low moved onto the west coast during the middle of the week, and advanced east through the Rockies during the end of the week.  Strong warm air advection took place over the top of a shallow polar airmass that was in place over Iowa.  The east-southeasterly flow at the surface drew cool and dry air into the state from the east, setting the stage for a significant ice storm.  The main area of precipitation overspread the state during the early morning hours of the 24th and persisted through much of the 25th.  Initially, very warm air aloft meant that the precipitation fell in the form of freezing rain and sleet. 


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