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2025 Hazard Mitigation Plan Kittitas Gounty, Washington ffiLqffi#l Special Avalanche Bulletin lssued when significant public use is expected and dangerous avalanche conditions exist, but the avalanche conditions do not meet the level necessary to issue an Avalanche Warnino. This is an impact-based product. Avalanche Watch lssued when there is high confidence that warning conditions will develop within 24 and 48 hours of the forecast issuance. An Avalanche Watch will likely be upgraded to a warninq closer to the anticipated event. Avalanche Warning lssued when High avalanche danger is expected within 24 hours of the forecast issuance for many areas. Many areas can mean very large geographic areas or several aspects and/or elevations in a specific geographic area. Avalanche Warnings are not issued when the danger is high in specific or isolated areas. Furthermore, warnings can be issued when non-recreationalists or people who would not othenrvise access the avalanche forecast are expected to be adversely impacted. NWAC will always issue an avalanche warning when the danger is at least High or Extreme (per the NAPADS) in all three (3) elevation bands - below treeline, near treeline and above treeline. DefinitionType Table 4-24. Northwest Avalanche Center Avalanche Advisories 4.6.1.4. Probability and Frequency The probability of occurrence for an avalanche occurring in Kittitas County is high because avalanche events occur annually. According to the 2023 Washington State Enhanced Hazard Mitigation Plan, the probability of a future avalanche related disaster declarations each year is less than 1% in the State. Avalanches occur regularly every year in mountain areas. Many weather and terrain factors determine avalanche danger. At lower elevations of the Cascades, the avalanche season begins in November and continues until the last remnants of snow have melted in early summer. ln the high alpine regions, the hazard continues year round. Hundreds of thousands of avalanches are thought to occur each year in the Cascades. While the probability of avalanches occurring each year is very high, there is a very low impact on the planning area due to the remote locations of events and mitigation efforts along developed areas. Avalanches along two (2) main mountain highway passes are limited due to ongoing mitigation to control slides during the winter months. The avalanche annualized frequency value represents the average number of recorded avalanche hazard occurrences, in event days, per year over the period of record. Table 4-25 outlines the annualized frequency for avalanches, based on FEMA NRI data, for Kittitas County. Table 4-25. Avalanche Annualized Frequency (FEMA National Risk lndex) 4.6.1.5. Pasf Events Avalanches occur frequently each year and kill, on average, one (1) to two (2) people annually in Washington and about 28 people annually in the United States.-63'"64 Avalanches have killed more people in Washington than any other hazard during the past century. ln 90% of avalanche fatalities, the weight 63 Washington Emergency Management Division. (n.d.).Avalanche. Retrieved from https://mil.wa.qov/avalanche 6a Federal Emergency Management Agency. (n.d.). Avalanche: lmpact. Retrieved from https://communitv.fema.gov/ProtectiveActionsis/article/Avalanche-lmpact. Kittitas County 7 0.1 events per year Annualized frequency is defined as the expected frequency or probability of a hazard occurrence per year. Annualized FrequencyLocationEvents on Record 1960 - 2019 Chapter 4: Hazard ldentification and Risk Assessment 73