Avalanche forecast

West Slopes North

Northwest Avalanche Center
View on map

Avalanche danger

Tue
Alpine
4 · High
Treeline
3 · Considerable
Below
3 · Considerable
Open full map
Out of date — this forecast expired 3 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

A powerful storm will bring heavy snow, strong winds, warmer temperatures, and also some rain to lower elevations. Avoid all avalanche terrain including big slopes overhead when the storm is at its peak or if you see widespread signs of instability like shooting cracks or natural avalanches.

Avalanche problems

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–2.5

    As usual West North is getting the lion's share of the precipitation and snowfall with the next storm. While this is always a great thing in a lot of ways - and probably the reason you are reading this forecast instead of for another zone in the Cascades - it doesn't come without some dangers.   The forecast of 2" to 3" of precipitation will equal 2-3' of new snow in the next 24 hours. Temperatures will also be a bit warmer than we have seen with any other storm in the last month or two.  While we have gotten used to cold dry powder falling on settled snow, be ready for dense slabs and upside-down snow conditions Monday.

    A natural cycle of large slab avalanches is not a sure thing, but given the weather forecast it seems pretty likely we will see some Monday morning.  The best policy will be to start with the simplest, least exposed terrain and see how the storm pans out. Temperatures will cool, winds and snowfall will taper and avalanche danger should start to decrease by the end of the day. If it stays stormy into the afternoon then it's probably best to finish the day in simple terrain as well.

     

    (4/20/2022)

    Wide crown from a very large natural avalanche last spring.

    Photo: Colin Wiseman

  • Loose Wet

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–2

    Some level of wet avalanche activity is likely with snow levels rising overnight and putting some rain on the cold and dry snow we have enjoyed lately. Rain and thick wet snow are hard to ignore so this problem shouldn't take you by surprise. Pay attention to slopes overhead and look for signs of instability like pinwheels, rollerballs, or snow shedding from trees and rocks. Don’t linger directly under steep slopes if you start seeing any of the above.

    In addition to wet loose avalanches, larger-than-average cornices will start to sag with warmer temperatures. They will eventually get primed up to come crashing down and lay waste to anything in their path. They can also trigger large slab avalanches where a single person or even a group of people would not. Keep track of what is above you be it a large cornice or steep slopes producing rollerballs or other signs of wet avalanche instability. It's up to you to stay out of the way.

    Example of small (D1) loose wet avalanches from last winter. Though these are not nearly big enough to fully bury a person, they still pose a significant danger in terrain with creeks, gullies, rocks, etc. in the track or runnout. 

     

Avalanche Discussion

Active wind loading was reported from around West North today. Strong south winds ahead of the next storm kicked up snow and built fresh slabs near and above treeline.  Two wind slab avalanches were reported from the vicinity of Ptarmigan Ridge with one being very large and possibly cornice triggered (photo) - the exact timing is uncertain. A few sunny, lower elevation slopes produced rollerballs and small wet loose avalanches, but strong winds and moderate temps kept warming in check for the most part.

An unexpected 8-12” of new snow fell across the zone Friday night with avalanche activity reported from multiple subzones Saturday. Observers in the Baker Backcountry observed numerous natural and human triggered slab avalanches. Though small in size they remained reactive into the afternoon.  Continued snowfall partly filled-in some crowns and bed surfaces by the end of the day. An observer on Ruby Mountain found 8" of light density new snow.  The new snow had just enough cohesion to produce soft slab avalanches at the old/new snow interface. The wind was strong enough to transport snow above 6500' and shooting cracks were observed as they climbed into more wind affected terrain. An NWAC Forecaster at Schriebers/Baker NRA reported 10” of new snow at treeline from snowfall overnight but no wind transport was reported at treeline.

 

Regions covered