Avalanche Forecast
Regions: Cascades - North West.
Significant snow fall and wind has created very dangerous avalanche conditions in the Mt Baker backcountry. While the likelihood of natural and human triggered avalanches is decreasing Monday, very large and destructive avalanches can still occur. Pay attention to terrain above you and avoid areas where large avalanches may run and stop.
Detailed Forecast
Monday will bring a relative break in the weather with decreasing snow showers, decreasing winds, and increasing visibility. While this will allow the avalanche danger to decrease, very dangerous avalanche conditions will continue with the possibility for very large and destructive avalanches.
Wind slabs have been reported at all elevations. Many of these wind deposits are very deep. Wind slabs may step down into older weak layers formed early in the storm and entrain significant amounts of snow allowing avalanche to grow larger than expected.
Warming temperatures Sunday formed storm slabs over the cold light snow from Saturday. Storm slabs will become increasingly difficult to trigger but have the possibility to grow large and travel significant distances.
Extra caution should be taken if traveling in the backcountry on Monday. Natural avalanches are becoming less likely but are not out of the question. Due to significant amounts of new snow, avalanche may become much larger than you might expect. Be aware of overhead terrain where avalanches may run well into the tracks and runouts.
Deep snow exists throughout the Mt Baker area. Snow immersion and tree-well hazards continue to increase and pose significant danger. Maintain constant communication with your travel partners.
Snowpack Discussion
A very active weather pattern targeted the Mt Baker area Wednesday through Sunday night. Three to five feet of snow sits above the most recent melt-freeze crust.
High snowfall intensities, warming air temperatures, and strong winds created significant weak layers within the upper snowpack Sunday. [Note that the strong winds have not been accurately represented by the NWAC station data from Mt. Baker due to riming of the wind sensor late Saturday night and Sunday morning].
Strong winds transported snow forming wind slabs on a variety of aspects. Many of these wind slabs are very deep.
Poor visibility limited observations near and above treeline Saturday and Sunday. A natural avalanche cycle likely occurred Sunday but is currently not verified.
Observations
Saturday Mt Baker ski patrol reported generally soft surface snow conditions with limited slab development in sheltered areas. While winds were decreasing, wind transportation from Friday night was observed near treeline.
On Friday, NWAC professionals traveled to near treeline in the Baker backcountry. They avoided exposed terrain above treeline due to potential for large and dangerous wind slabs. Active wind transport and new snow occurring throughout the day redistributed the deep storm snow. There was evidence of a large wind slab avalanche near treeline on a N-facing slope.
Avalanche Problems
Wind Slabs
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.
Aspects: All aspects.
Elevations: All elevations.
Likelihood: Very Likely
Expected Size: 1 - 2
Storm Slabs
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.
Aspects: All aspects.
Elevations: All elevations.
Likelihood: Likely
Expected Size: 1 - 1