4.7 SR 06-01-2020 - Laserfiche WebLink

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Sherburne County Multi -Hazard Mitigation Plan, 2020 To determine the probability of future winter storm events in Sherburne County, all past -observed winter -related storm events (i.e. blizzard, heavy snow, ice storm, lake -effect snow, sleet, winter storm, and winter weather) and the period in which they occurred are examined. Based on the records in the NCEI Storm Events Database, the relative frequency of winter -related storm events in the County is 2.7 events per year. This relative frequency can be used to inferthe probability of these events occurring in the future. Severe Winter Storms and Climate Change Historically, winter storms have had a large impact on public safety in Minnesota. This will continue, with a possible increase in snowstorm frequency and annual total snowfall. Winter weather is often a cause of power outages. Pressures on energy use, reduced reliability of services, potential outages and the potential rise in household costs for energy are major climate change risks to public health. According to the 2015 Minnesota Weather Almanac, a recent study of seasonal snowfall records across the state from 1.890-2000 showed that 41 of 46 climate stations recorded an increase in average annual snowfall, by as much as io inches. Higher snowfall levels can result in greater runoff potential during spring snowmelt, and many watersheds in Minnesota have shown more consistent measures of high - volume flows during spring, often at or above flood stage (Seeley M. , 203.5). Severe Winter Storms and Electrical Outages The leading cause of electric outages in Minnesota during 2oo8 to 203.3 was weather/falling trees. Between 2oo8 and 203.3, the greatest number of electric outages in Minnesota occurred during the month of March (U.S. Department of Energy, 203-5). Vulnerability The number of heavy snowfall years forthe Midwest has fluctuated between igoo and 2oo6. The periods of 1900-3.92o and 3.96o-3.985 had numerous years with snowfall totals over the gosh percentile. In the past three decades, the number of heavy seasonal snowfall totals has been much lower. Despite these generally lower seasonal snowfall totals, some areas of the Midwest have still experienced significant snow totals in the most recent decade. The ioo-year lineartrends based on decadal values show that the upper Midwest had statistically significant (i% level) upward lineartrends in snowstorm frequency from 1901 to 2000 (Kunkel, et al., 2013). Winter storms affect Sherburne County each year, so there is a i00% probability that the county and its jurisdictions will be affected annually. The amount of snow and ice, number of blizzard conditions, and days of sub -zero temperatures each year are unpredictable and within Sherburne County the vulnerability ofjurisdictionsto winter storms does not vary geographically. Citizens living in climates such as these must always be prepared for situations that put their lives or property at risk. It is not always the size of the storm or the depth of the cold, but an unprepared individual with a vehicle breakdown or lack of a personal winter safety kit that are at risk. Rural citizens are more vulnerable to issues with deep snow. Page 167