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Archived

Avalanche Forecast

Jan 25th, 2018–Jan 26th, 2018
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
3: Considerable
The avalanche danger rating at treeline will be considerable
Below Treeline
3: Considerable
The avalanche danger rating below treeline will be considerable
Alpine
4: High
The avalanche danger rating in the alpine will be high
Treeline
4: High
The avalanche danger rating at treeline will be high
Below Treeline
3: Considerable
The avalanche danger rating below treeline will be considerable

Dangerous avalanche conditions will persist on Friday due to additional light snowfall, an uptick in wind transported snow, and cold temperatures preserving recent storm instabilities. Avoid steep open slopes connected to large avalanche paths until we exit this storm cycle. Give safe margins near and below growing cornices. Tree-well and snow immersion hazards are very dangerous, so keep communication with your partner at all times. 

Detailed Forecast

Dangerous avalanche conditions will persist on Friday due to additional light to moderate snowfall, an uptick in wind transported snow near and above treeline, and cold temperatures preserving recent storm instabilities. Due to lower density surface snow available for transport and moderate W-SW winds forecast above treeline, wind slabs may develop below treeline or further downslope than you might expect Friday.  Avoid travel on slopes if you encounter wind stiffened surface snow, especially on steeper exposed terrain and steep roll-overs.  

The potential for large and destructive avalanches remains in bigger terrain. Avoid travel on or below slopes connected to large avalanche paths until we exit this storm cycle. Give safe margins near and below growing cornices. There's plenty of good snow out there, so maintain a conservative approach to terrain selection. 

Significantly transformed snow conditions have taken place during this extended storm cycle. Tree-well and snow immersion hazards are very dangerous, so keep communication with your partner at all times.

Snowpack Discussion

An extended storm cycle continues. Over the past 8 days, Mt Baker has received roughly 9 ft of storm snow!  Cool temperatures beginning Wednesday night have slowed the rate of settlement of the most recent storm snow. The most recent 1/18 crust is several feet down. Cool and generally light showers were seen on Thursday with increasing snowfall intensity early Thursday evening.  

Warming early Wednesday, along with heavy snowfall and strong winds led to a widespread natural avalanche cycle. Slab avalanches of 2 ft or more were common and traveled long distances. Avalanches were releasing in terrain well below treeline leading to an update and issuance of an avalanche warning in this zone.

Poor visibility and frequent storm conditions have limited observations above treeline during this period. 

Observations: 

Wednesday, Mt Baker Pro Patrol reported a very active avalanche cycle was ongoing. There were large natural avalanches releasing from Shuksan Arm and all avalanche paths in area were sensitive to ski triggering with slabs of 2 ft or more running long distances.  

On Tuesday, NWAC Pro Observer Lee Lazara was in the Baker Lake area in below treeline terrain where he experienced significantly less snow accumulated above the recent crust (approximately 2') relative to Bagley Lakes. New storm instabilities had not yet developed in this location.

Avalanche Problems

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

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: Alpine, Treeline.

Likelihood: Likely

Expected Size: 1 - 2