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2025 Hazard Mitigation Plan <br />Kittitas County, Washington <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.9., 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 />DescriptionType <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. ln 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-l 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 />e.-lr*ft <br />t"6 <br />gF r:9 <br />+Tic nspo r.l3 tir rr Ri ut€s Vu ln€ ra tJ l€ lo Av,it 13 nchs <br />Rscrsetiisr A$.g.s Vulnerabls to A"leHnchs <br />Bpproxlrrale er,eei <br />xefil rar*e +tgir*tll, <br />'/tET$- |f <br />lhEii: <br />tuc <br />EIllltr <br />8a{Garl.r fif-'i*rf <br />ftrr.,4:.: <br />.*:ry <br />Ltr+r 5F443-a <br />Garrts4+ <br />?lrnvr$rf, <br />CFa31 <br />S-{iar <br />8tr3'"d ii.:t+: <br />Earyr <br />dlrar: <br />grin66l F:rr- *r,F a Frlr <br />li#it i'slilrrlEdr Frrr <br />YEtr:ftFEr <br />Ext.-:rl <br />4.6.1.3. Hazard ExtenUlntensity <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 <br />Chapter 4: Hazard ldentification and Risk Assessment 71