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2025 Hazard Mitigation Plan <br />Kittitas County, Washington <br /> <br /> <br />Chapter 4: Hazard Identification and Risk Assessment 199 <br />The NWS Pendleton, Oregon Area Forecast Office is responsible for issuing winter weather advisories, <br />as conditions warrant. Table 4-151 outlines the winter weather advisories.263F <br />263 <br />Table 4-151. NWS Winter Weather Advisories <br />Type Definition <br />Winter Weather Advisory <br />Issued when snow, blowing snow, ice, sleet, or a combination of these wintry <br />elements is expected but conditions should not be hazardous enough to meet <br />warning criteria. Be prepared for winter driving conditions and possible travel <br />difficulties. <br />Winter Storm Watch <br />Issued when conditions are favorable for a significant winter storm event (e.g., heavy <br />sleet, heavy snow, ice storm, heavy snow and blowing snow, or a combination of <br />events). <br />Winter Storm Warning <br />Issued for a significant winter weather event including snow, ice, sleet or blowing <br />snow, or a combination of these hazards. Travel will become difficult or impossible in <br />some situations. <br />Blizzard Warning <br />Issued for frequent gusts greater than or equal to 35 mph accompanied by falling <br />and/or blowing snow, frequently reducing visibility to less than 1/4 mile for three (3) <br />hours or more. A Blizzard Warning means severe winter weather conditions are <br />expected or occurring. Falling and blowing snow with strong winds and poor <br />visibilities are likely, leading to whiteout conditions making travel extremely difficult. <br />Ice Storm Warning <br />Usually issued for ice accumulation of around 1/4 inch or more. This amount of ice <br />accumulation will make travel dangerous or impossible and likely lead to snapped <br />power lines and falling tree branches. <br />Details on extreme cold weather advisories (i.e., wind chill, freeze and frost advisories, watches, and warnings) are available under the <br />Severe Weather section of this Plan. <br /> <br />The Winter Storm Severity Impact Index (WSSI) is a tool that assists NWS operational forecasters in <br />maintaining situational awareness of the possible significance of weather related impacts based upon <br />the current official forecast. Additionally, it helps enhance communication to external partners (e.g., <br />emergency managers, public safety officials), media, and general public of the expected severity of <br />potential societal impacts due to the expected winter weather hazards and their distribution. Table 4-152 <br />outlines the WSSI impact definitions.264F <br />264 <br />Table 4-152. NWS Winter Storm Severity Index <br />Index Description <br /> Winter Weather Area Expect Winter Weather. <br />• Winter driving conditions. Drive Carefully. <br /> Minor Impacts Expect a few inconveniences to daily use. <br />• Winter driving conditions. Use caution while driving. <br /> Moderate Impacts <br />Expect disruptions to daily life. <br />• Hazardous driving conditions. Use extra caution while driving. <br />• Closures and disruptions to infrastructure may occur. <br /> Major Impacts <br />Expect considerable disruptions to daily life. <br />• Dangerous or impossible driving conditions. Avoid travel if possible. <br />• Widespread closures and disruptions to infrastructure may occur. <br /> <br />263 National Weather Service. (n.d.). Winter Weather Warnings, Watches, and Advisories. Retrieved from <br />https://www.weather.gov/safety/winter-ww. <br />264 National Weather Service. (2023). Winter Storm Severity Index (WSSI): Product Description Document. <br />Retrieved from https://www.wpc.ncep.noaa.gov/wwd/wssi/WSSI_PDD_2022-23.pdf.