Avalanche Forecast

Close to another foot of snow fell Wednesday, adding to already impressive storm snow totals from the past week. Strong winds may have created unstable wind slabs on leeward slopes near ridgelines and on the sides of gullies. Expect to encounter larger and more reactive wind slabs along with deeper and drier snow as you travel up in elevation, particularly above Tuesday’s rain line. Fresh cornices, blowing snow, and smooth pillow-like features are signs that wind effect has taken place and wind slabs are possible. If these signs are present, avoid slopes greater than 35 degrees and don’t travel below fresh cornices. 

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.

Don’t overlook the huge volume of water we just received in a relatively short amount of time on top of the New Year’s Day crust. Although natural avalanche activity is trending downward, several notable avalanches as large as D3 in the neighboring West North zone have been reported in the past few days. Use caution on slopes 35 degrees and steeper, convexities, and unsupported slopes where you could trigger avalanches more easily. 

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.