Register
Get forecast notifications
Create an account to receive email notifications when forecasts are published.
Login
Archived

Avalanche Forecast

Feb 7th, 2015–Feb 8th, 2015
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
2: Moderate
The avalanche danger rating at treeline will be moderate
Below Treeline
2: Moderate
The avalanche danger rating below treeline will be moderate
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
2: Moderate
The avalanche danger rating at treeline will be moderate
Below Treeline
2: Moderate
The avalanche danger rating below treeline will be moderate

Expect a decreasing avalanche danger Sunday with a break between systems. Watch for areas where more significant new snow has accumulated, mainly above treeline and on the volcanoes where new storm and wind slab are likely. 

Detailed Forecast

A break between systems is expected during the daylight hours Sunday. This should give time for any recent shallow storm slab or wet new snow to settle and possibly refreeze to form new surface crust layers. This should allow for a slightly decreasing danger at higher elevations where more recent snow may have accumulated. Watch for wind transported new snow on some higher elevation lee slopes, mainly N-E facing.

The snowpack below treeline should continue to drain, but small wet loose avalanches will still be possible on steeper slopes below treeline. 

Do note as a result of the unseasonably low snowpack, especially at lower elevations, numerous terrain hazards such as open creeks, partially covered rocks and vegetation are widespread.  

Snowpack Discussion

Yet one more cranked facet of warm and wet weather over the past three days has put another soaking into the meager snowpack that remains. I will not mention the amounts of greatest recent rainfall, nor where it fell, but it may have been near where the record annual snowfall occurred! However, there has been some cooling Saturday along with more precipitation and wet snowfall above about 4000 feet in the north and 5000 feet in the central and south. Reports Saturday afternoon indicate about 2 to 6 inches of wet snow has accumulated above these mentioned elevations.

The wet snow overlies previous rain soaked snow and there was no strong distinctive bed surface. Very little in the way of avalanche activity was reported other than a few small purposefully triggered slides by the Crystal Patrol, testing the 4 inches of wet snow in the upper mountain. There was just beginning to be enough accumulation to initiate isolated slides that behaved more like wet snow avalanches rather than slab releases. 

The Mt Baker patrol Saturday, tested the about 2 feet of unsupported and saturated snow overlying rock bed surface with 50 lb explosive charges, with no results. Some slopes now have glide cracks opening, more typical of late spring. 

Observer Tom C. was in the Rainy Pass area near Stevens on Thursday. With a transition to rain in the late morning, Tom observed natural small wet loose and wet slabs releasing on steeper slopes below treeline involving the most recent snow over a rain crust. Wet loose involving the most recent snow were also ski cut by professional patrollers at Crystal and Alpental Thursday.  By Friday, no significant wet loose slides were observed below treeline by professional patrols across the west slopes.  Dallas Glass in the Skyline area of Stevens on Friday found above 5000 feet (approaching near treeline), there was enough recent storm snow for more significant natural or skier triggered wet snow avalanches and observed pinwheeling of the surface snow.     

Small wet loose, Rainy Creek. 2-5-15 by T. Curtis

The mid and lower snowpack west of the crest should consist of layers of stable consolidated rounded grains or melt forms and crusts from multiple warm periods this winter.

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: North, North East, East, South East, North West.

Elevations: Alpine, Treeline.

Likelihood: Possible

Expected Size: 1 - 1

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: Alpine, Treeline.

Likelihood: Possible

Expected Size: 1 - 1