Stevens Pass Avalanche Forecast

Issued: Dec 28th, 2013 10:00AM

Sat Dec 28th Current Conditions
Alpine Moderate Treeline Moderate Below Treeline Low
Sun Dec 29th 2 Day Outlook
Alpine Moderate Treeline Moderate Below Treeline Low

The alpine rating is moderate, the treeline rating is moderate, and the below treeline rating is low. Known problems include Wind Slabs.

A mixture of supportable or breakable crusts with protected areas maintaining some shallow soft snow over firm underlying and well consolidated snowpack.

Summary

Detailed Forecast

Becoming mostly cloudy Sunday in the north part with a chance of a little light rain or snow along with some cooling. Any light precipitation that may fall Sunday should not change the overall mostly low avalanche danger.

Only mid or high clouds are expected in the central to south part of the zone. 

Above treeline some isolated pockets of wind slab may persist below ridges mainly on shaded high elevation northerly facing terrain. 

Snowpack Discussion

Most areas have a mix bag of surface snow conditions given the lack of recent storm activity as well as periodic warm temperatures, sunshine, rain or shallow new snowfall.  The snowpack can be characterized by a mixture of supportable or breakable crusts with sun and wind protected areas maintaining some shallow soft snow over a firm underlying and well consolidated older snowpack. 

The last avalanche activity of note occurred following a series of frontal passages and warming temperatures from December 20-23. This caused 1-2 feet of heavy snow in the alpine and some very wet snow and rain near and below treeline. The Mt Baker area professional patrol reported widespread 4-14 inch sensitive ski triggered wind slabs on December 20-21 while a professional guide reported a large wet slab avalanche running from Chair Peak near Snoqualmie Pass December 22, along with other signs of wet snow instability.

Other recent observations over the past few days include stable surface crusts, a few minor wet-loose triggered avalanches on solar aspects above treeline as well as some settled powder near treeline on non-solar aspects. Snow profiles and tests at Alpental Thursday should generally stable snow well bonded snow but a few high quality but hard to trigger shears were noted about 60 cm below the surface above old crust layers within softer melt-form crystals. 

The avalanche danger will continue to be low at the lower elevations due to our ongoing lower than normal snowpack. Non-avalanche hazards such as exposed rocks, creeks, and icy surfaces exist and present a travel challenge.

 

Problems

Wind Slabs

An icon showing Wind Slabs

Likelihood

possible

Expected Size

1 - 1

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.

Valid until: Dec 29th, 2013 10:00AM

Forecast Trend

The latest forecast danger ratings, broken down to elevation. See how an elevation is trending.