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Archived

Avalanche Forecast

Jan 23rd, 2018–Jan 24th, 2018
Alpine
4: High
The avalanche danger rating in the alpine will be high
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
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

The avalanche danger will lower slightly during the day on Wednesday, but the potential for triggering a large avalanche or even a very large avalanche above treeline remains. Recent storm and wind slabs require time to heal, so be patient and match your terrain selection appropriately and avoid avalanche run and stop zones. Tree-well and snow immersion hazards are very dangerous, so keep communication with your partner at all times.

Detailed Forecast

A frontal system will continue to bring significant snowfall to the west slopes of the Cascades Tuesday night, with moderate to occasionally strong crest-level winds and a slight warming trend. On Wednesday, rain and snow showers will be light to occasionally moderate along with lighter crest-level winds. 

Storm slabs developing in many areas Tuesday afternoon will build to 1-2' in many areas by Wednesday morning. Storm slabs will remain touchy Wednesday, with the potential to entrain the deeper lower density snow from the past week that exists in all areas, allowing these slabs to run farther and become larger than you expect. Stick to lower-angle terrain that is well-supported or heavily terrain anchored. 

Moderate winds are transporting the new snow, particularly near and above treeline. These will continue to build touchy large or even very large wind slabs near and above treeline on a variety of aspects. New or recent wind slabs may also produce large avalanches, entraining significant amounts of deeper loose dry snow. Avoid above treeline terrain, terrain avalanche runout zones or wind-loaded terrain elsewhere and consider any aspect to be fair game for wind slabs on Wednesday.

Light to moderate rain will likely mix up to 3000-3500 feet on Wednesday morning. Loose wet hazard will not be listed as an avalanche problem here, but may be encountered at the very lowest elevations.

The avalanche danger will lower slightly during the day on Wednesday, but the potential for triggering a large avalanche or even a very large avalanche above treeline remains. Recent storm and wind slabs require time to heal, so be patient and match your terrain selection appropriately and avoid avalanche run and stop zones. Tree-well and snow immersion hazards are very dangerous, so keep communication with your partner at all times.

Snowpack Discussion

A very active weather pattern over the last week continues to target the Mt Baker area. A significant storm is currently bringing 1-2' of storm snow by Wednesday morning in most locations along with a gradual warming trend and moderate warming is creating a thick storm slab layer, with wind slabs developing in near and above treeline terrain. Large natural avalanche activity was reported in the Mt. Baker vicinity on Tuesday.

Below the recent storm snow, more than 5 feet of settling lower density snow sit above the most recent melt-freeze crust - it is deep out there! 

Strong winds during Sunday's storm transported snow forming wind slabs on a variety of aspects creating very deep wind slabs particularly near and above treeline. Storm slabs were easy to trigger on Sunday and again on Monday and were running long distances. 

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

Observations: 

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. There were various resistant planar interfaces within the storm snow from the past several days and the interface with the weak wet snow above a January 18th crust yielded hard test results.

On Tuesday, Mt. Baker Pro Patrol reported that a large avalanche was heard in the vicinity of Mt. Shuksan.

An avalanche professional in the Glacier Creek area reported little wind and occasionally heavy snow showers on Monday. A reactive storm layer within the most recent storm snow allowed storm slabs of 6-10" to be easily triggered on all aspects up to 5600'.  A few natural storm slabs were observed as well. 

On Monday morning, Mt. Baker pro-patrol reported control results producing widespread and easily-triggered 1'+ soft slab or loose dry avalanches that broke wide and ran far.  Poor visibility prevented observations into the surrounding backcountry terrain. 

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: All elevations.

Likelihood: Likely

Expected Size: 1 - 2