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2024 Hennepin County All -Jurisdiction Hazard Mitigation Plan <br />Volume 2 — Hazard Inventory <br />Southwest Minnesota Ice <br />Storm, April 9-11, 2013. <br />A slow -moving low-pressure <br />system pumped copious <br />amounts of moisture up into a <br />subfreezing air mass, resulting <br />in up to 48 hours of nearly <br />continuous freezing rain in <br />southwestern Minnesota, <br />eastern Nebraska, <br />northwestern Iowa, and <br />eastern South Dakota. Just <br />north of the freezing rain, <br />heavy, wet snow accumulated <br />6-14 inches. In southwestern <br />Minnesota, hundreds of trees <br />and power poles were snapped <br />by the ice, which accumulated <br />to nearly 1" thick near Worthington. Extensive secondary damage occurred to residences and <br />vehicles, as tree limbs snapped off and crashed through windows. Power outages lasted days in <br />some areas. Governor Dayton issued Executive Order 13-03, to authorize state assistance for <br />recovery efforts in southwestern Minnesota. <br />There have been no other incidents that are within the scope of this plan. <br />4.3.13.8. Future trends/likelihood of occurrence Ble <br />Little is known about future trends with respect to ice storm activity. On one hand, damaging ice storm <br />frequency may decrease, as more and more winter events fall as above -freezing liquid. Another argument <br />is that more events that would have been snowstorms will contain freezing rain, and hence, more ice <br />storms. Yet another line of reasoning suggests that increased wintertime moisture will result in more heavy <br />precipitation events, including heavy rain and freezing rain. The topic has received little research attention, <br />so there is virtually no "consensus" about what is likely to happen. <br />4.2.13.9. Indications and Forecasting <br />The Twin Cities/Chanhassen forecast office of the National Weather Service is the official forecasting <br />authority for major winter weather events affecting Hennepin County, including ice storms. High -intensity <br />winter storms are usually well anticipated by the numerical weather prediction models, often up to a week <br />in advance, and forecasters tend to have high awareness of potentially dangerous winter conditions two <br />days or more before they develop. The potential for significant ice accumulation 1-3 days out is also <br />monitored by the Weather Prediction Center, at NOAA/NWS headquarters. <br />4.3.13.10. Detection & Warning <br />Warning authority for ice storms also lies with the Twin Cities/Chanhassen forecast office of the National <br />Weather Service. An urgently severe ice storm will be covered by an Ice Storm Warning, which indicates <br />211 <br />