Avalanche forecast

West Slopes North

Northwest Avalanche Center
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Avalanche danger

Tue
Alpine
4 · High
Treeline
4 · High
Below
4 · High
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Out of date — this forecast expired 6 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

Very dangerous avalanche conditions exist, and travel in avalanche terrain is not recommended.  High rates of snowfall and strong winds are continuing through Monday night.  Numerous avalanche involvements occurred in the last 48 hours, so the best thing to do is stay out of all avalanche terrain including the runouts beneath steep slopes while the storm continues. 

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Very Likely
    Size
    1–3

    You can trigger a very large avalanche as snow continues to build on Monday. Here is a report of an avalanche involvement which was submitted to the NWAC site on Saturday.  This skier triggered the avalanche from below, indicating a very touchy snowpack, and also making it very difficult to avoid getting caught in. Reporting this information is extremely valuable for informing the public how widespread weaknesses in the snowpack are and we truly appreciate receiving this information. 

    Sunday night and all day Monday snowfall will continue, with another 3in of water (up to 3ft of snow) forecasted. Winds will remain strong, and slabs will continue to develop, forming into deposits several feet thick. Reports are varying about the depths avalanches are failing at. Some appear to be within the new snow layer, while some are failing at the Jan 24 crust which was on the surface before snowfall began a week ago.  Failures near the Jan 24 crust could involve persistent weak layers, meaning that avalanches may be more reactive and propagate further if a persistent weak layer is involved. Regardless of what the avalanche fails on, conditions are very dangerous right now and give avalanche paths including runouts a wide berth.

    A small avalanche which was skier triggered on a test slope in the Heather Meadows area on 1/30 Photo: Pete Durr

  • Loose Wet

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1

    Snowline is hovering in the 3500 to 4000ft range on Monday, so expect to see small wet loose avalanches at lower elevations. They may fail naturally in steep areas, especially near trees and rocky outcroppings. If the snow is moist, the first indicators of weakness are usually rollerballs or pinwheels before an avalanche entraining more snow comes down the slope.

    A wet loose avalanche that occurred near rocks on a steep slope. Photo: Zach McGill

Avalanche Discussion

Backcountry users on Sunday reported that the snow was fairly supportable so they were still able to have a good time getting out on lower angle slopes.  That is a great plan as we ride out this storm for the next couple days.  This week we've made up for the period of high pressure in the preceding weeks. As I write, the Heather Meadows weather station reported nearly 5in of water in the last 7 days, and an increase of 25in on the settled snow base, bringing the total to 154in.  For nearly the entire day on Sunday around a tenth of an inch of water was recorded every hour.  A tenth of an inch of water or more per hour is an indicator that the snowpack is rapidly being loaded, and oftentimes it means the snowpack cannot adjust quickly enough and, as a result, avalanches occur. 

During the ongoing Covid-19 pandemic, continue to follow the latest guidance from local, state, and federal health officials. Avoid unnecessary risks that could impact first responders and stress medical resources.  Wear a mask when appropriate, practice social distancing, and consider recreating closer to home.

 

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