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2025 Hazard Mitigation Plan <br />Kittitas County, Washington <br /> <br /> <br />Chapter 4: Hazard Identification and Risk Assessment 71 <br />Type Description <br />Cornice Fall <br />An overhanging mass of wind-deposited snow that breaks off of a ridgeline and tumbles <br />down the slope. Cornices typically form on the leeward side of a sharp, wind-exposed <br />terrain break (e.g., a ridge crest or summit). Cornice falls can trigger additional slab <br />avalanches on the slope below, or they can simply consist of the cornice and any <br />additional snow entrained by the cornice blocks. Accidents typically involve cornices <br />breaking unexpectedly below ridgeline travelers, or occasionally from natural cornice <br />falls that overtake travelers on slopes below. <br />4.6.1.2. Hazard Location <br />The Cascade Range in the western half of Kittitas County receives extensive precipitation due to its size <br />and orientation to the flow of Pacific marine air. In the local maritime climate, it is common for air <br />temperatures to rise above freezing and for precipitation to change from snow to rain during mid-winter <br />storm cycles. Temperatures can change several degrees within minutes, causing abrupt changes in <br />precipitation type. These conditions frequently cause the release of avalanches. Figure 4-1 shows the <br />areas vulnerable to avalanches in Washington State, including the westernmost portion of Kittitas County, <br />which includes the Snoqualmie Pass. The majority of this area is included in Unincorporated Kittitas <br />County. The cities of Roslyn and Cle Elum, and the Town of South Cle Elum are located on the edge of <br />this hazard area. Due to their location on the periphery and mitigation efforts, these jurisdictions have <br />very low levels of risk from avalanche. <br />Figure 4-1. Areas Vulnerable to Avalanches <br /> <br />4.6.1.3. Hazard Extent/Intensity <br />The Northwest Avalanche Center (NWAC) produces daily avalanche forecasts for 10 zones across the <br />State of Washington and northern Oregon during the winter season. Field-based avalanche forecasters