menu

West Slopes North - Canadian Border to Skagit River

Issued: 3:02 PM PST Saturday, March 3, 2018
by Robert Hahn

While the Avalanche Danger is decreasing, dangerous conditions remain above treeline. You can trigger Wind Slabs near and above treeline and Persistent Slab avalanches on sunny slopes in the upper snowpack. Avoid wind loaded areas and large open sun-exposed slopes 35 degrees and steeper. 

Danger Scalei
  • No Rating (Info Avail)
  • Low (1)
  • Moderate (2)
  • Considerable (3)
  • High (4)
  • Extreme (5)

Avalanche Problems for Saturday

Wind Slabi

  • Avalanche Problemi
  • Aspect/Elevationi
  • Likelihoodi
  • Sizei
 

Persistent Slabi

  • Avalanche Problemi
  • Aspect/Elevationi
  • Likelihoodi
  • Sizei
 

Forecast for Saturday:

You are most likely to trigger Wind Slab avalanches above treeline, today. You can avoid these avalanches by staying off of recent snow drifts, deeply pillowed features, and fresh cornices on slopes 35 degrees and steeper. These areas may exist far below ridge-lines and on mid-slope cross-loaded features. Soft non-wind-effected snow may cover new wind slabs making them harder to identify. You may see some small loose avalanches release on the surface of steep slopes today. 

You may be able to trigger Persistent Slab avalanches in the upper snowpack on sun-exposed slopes greater than 35 degrees. If you dig about 2-3 feet below the surface you will find a series of thin sun crusts surrounded by very small facets. If you find this layer, avoid steep, open, sunny slopes as well as large avalanche paths to reduce your risk of these difficult to manage avalanches. In areas with a relatively shallower snowpack, avalanches triggered in the surface snow could step down to release a large and dangerous avalanche. These avalanches are difficult to trigger but the consequences are grave. The best way to avoid this low likelihood-high consequence problem is by avoiding triggering smaller avalanches in the surface snow.

Avalanche Summary:

About six inches of snow has accumulated in the last two days with up to four feet this week. New snow combined with moderate to strong winds transported snow in exposed terrain formed fresh wind slabs.

On E-S-W aspects, a thin breakable sun crust was formed early last week and buried on 2/23. Very small weak facets have been reported surrounding the crust. This layer has not yet had significant time to heal. It is found 2-3 feet below the surface on steeper slopes that have received direct sun during the past week.

Some observations suggest the presence of other persistent grains at this same interface on shaded slopes. Buried surface hoar and large preserved stellars have been reported in recent avalanches and snowpack tests at this interface.

Observers continue to report potential for a Deep Persistent Slab avalanche on a layer of weak sugary facets buried on 2/13. This weak layer is generally 3 to 5 feet below the snow surface just above a very firm melt-freeze crust (2/8). It's worth paying attention to this layer if your venturing into shallower areas. While these avalanches are unlikely, the consequences could be grave.

There are no significant layers of concern below the 2/8 crust.

Observations

On Wednesday NWAC professional observer Lee Lazzara traveled in the Mt Baker backcountry. Lee reported wind slabs forming on a variety of aspects near treeline. Snowpack observations showed a highly variable snowpack, but the facet/crust combination was found on steep sunny aspects 2 feet below the snow surface.

No Corresponding Mountain Weather Forecast Available