Avalanche Forecast

Storm slabs were confirmed on 12/23 and were widespread and reactive in control work at Mt. Hood Meadows. More snow has fallen at high intensity, so these slabs are expected to remain quite sensitive to human trigger on Monday. Avoid open slopes, convex rolls, unsupported slopes or slopes steeper than 35 degrees to keep yourself out of an avalanche.

Release of a soft cohesive layer (a slab) of new snow that breaks within the storm snow or on the old snow surface. Storm-slab problems typically last between a few hours and few days. Storm-slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.

You can reduce your risk from Storm Slabs by waiting a day or two after a storm before venturing into steep terrain. Storm slabs are most dangerous on slopes with terrain traps, such as timber, gullies, over cliffs, or terrain features that make it difficult for a rider to escape off the side.

Storm slabs usually stabilize within a few days, and release at or below the trigger point. They exist throughout the terrain, and can be avoided by waiting for the storm snow to stabilize.

Mt. Hood Meadows Pro Patrol reported two very large wind slab avalanches triggered by small explosives in previously uncontrolled terrain on 12/23. With moderate winds continuing to transport snow overnight, avalanche start zones will continue to load or reload. Winds will shift from westerly to easterly during the day, so don’t count on active wind loading patterns to indicate terrain where sensitive wind slabs have developed. Avoid open slopes and unsupported slopes steeper than 35 degrees located below ridge-features and keep in mind that very large avalanches may travel quite far.

Release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.

Wind Slabs form in specific areas, and are confined to lee and cross-loaded terrain features. They can be avoided by sticking to sheltered or wind-scoured areas..

Wind Slab avalanche. Winds blew from left to right. The area above the ridge has been scoured, and the snow drifted into a wind slab on the slope below.

Wind slabs can take up to a week to stabilize. They are confined to lee and cross-loaded terrain features and can be avoided by sticking to sheltered or wind scoured areas.