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2025 Hazard Mitigation Plan Kittitas County, Washington dry snow avalanche may turn into a wet snow avalanche as it moves down the mountain where the snow conditions change. The different types of avalanches are explained in Table 4-22..5s Table 4-22. Avalanche Types 5e Avalanche.org. (n.d.) Avalanche Encyclopedia: Avalanche Types. Retrieved from https://avalanche.orq/avalanche-encvcloped ial#avalanche-tvpe. An avalanche that breaks in dry snow. Dry snow can be found when the temperature is below freezing, and it is characterized by frozen ice crystals lacking moisture. Dry avalanches can be either dry loose avalanches or dry slabs. Dry snow fails when additional stress overcomes the strength of the snowpack, either from new snow loading, wind loading, falling cornices, or human triggers. Dry avalanches are characterized by relatively fast flow, often with a powder cloud. They are the most common type of avalanche encountered during typical mid-winter conditions and account for the maioritv of avalanche fatalities. Dry Wet An avalanche that breaks in or entrains wet snow. Wet snow is at its melting point, characterized by some amount of liquid water existing between snow grains. ln certain situations, increased liquid water content causes the snowpack to lose strength and avalanche. These wet avalanches can be released from a single point (wet loose) or as a cohesive slab (wet slab) and can occur from rain on snow, strong solar input, or warm temperatures. Although wet snow avalanches are typically slower than dry snow avalanches, they can move very quickly in steep and constrained terrain, and they produce very dense and destructive debris. They are commonly recognized by the presence of striations on the bed surface, debris leaves along the track, and snowballs in the debris. Wet avalanches account for fewer fatalities than dry snow avalanches. Accidents are often attributed to misjudging the timing of natural avalanches or underestimating the danqer of oettinq cauqht in slow-movinq wet snow debris. Hard Slab A slab avalanche of relatively dense, compacted snow. These slabs are hard and dense enough that it is difficult to push a single finger into them and are often characterized by hard, blocky debris. Hard slabs can be thin, formed from heavily wind compacted snow, or much thicker, formed as snow hardens under the weight of several storm events. Hard slabs are difficult to manage because stiffer slabs tend to give less feedback and are more likely to fail far above you. Hard slabs are notorious for unpredictable failures. You are most likely to trigger one from a thinner or softer part of the slab (e.9., near rock outcrops or near the edge of a slope). Soft Slab A slab avalanche of relatively soft, low density snow. These slabs are soft and low density enough that you can push a gloved hand or fingers into them. They are often characterized by soft, powdery debris. Soft slabs can vary in thickness, and most often form in the upper snowpack from recent storm events. Although soft slabs tend to give more feedback than hard slabs, they can still be triggered remotely or from below the fracture line, dependinq on conditions. An avalanche that releases from a single point and entrains cohesionless snow as it fans downhill. Loose snow avalanches (i.e., sluffs or point releases) vary in size, depending on how much snow is entrained and on the size of the terrain feature where they occur. Loose snow avalanches release immediately below their trigger point and are typically smaller and more predictable than slab avalanches. As a result, they cause fewer avalanche fatalities. Accidents involving loose snow avalanches often result from victims getting dragged into terrain traps (e.9., gullies, cliffs, couloirs, or trees). Wet loose avalanches can pack a heavier punch and qrow to very destructive sizes. Loose Snow Type Description Chapter 4: Hazard ldentification and Risk Assessment 70