Avalanche forecast

West Slopes South

Northwest Avalanche Center
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Avalanche danger

Tue
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
2 · Moderate
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Out of date — this forecast expired 5 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

Additional snowfall on Monday should continue to stress the snowpack in many areas of the zone. Make conservative terrain choices to help give these areas the time they need for the storm to play out. Instability may not be as obvious in areas receiving less snowfall, but the threat of avalanches still exists.

Avalanche problems

  • Storm Slabs

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

    Continued snow on Monday, specifically on the volcanoes and from White Pass southward will maintain our concern for Storm Slabs. The new snow may help to thicken existing slabs or create new slabs on top of the current snow surface. Slowly rising temperatures may also aid in the development of slabs by the end of the forecast period. Look for slab depth to increase as you ascend in elevation or in wind-loaded areas. You should look at the bond between the new and old snow by using quick hand pits as you travel.  Using test slopes and uptrack tests to see how all of the recent storm snow is reacting to your weight can give you more information to inform your terrain selection. If you find heavy snow over lighter snow, see cracking, or easily dislodge blocks of snow in your tests, then you should avoid slopes over 35 degrees.

    If you are in an area of the zone further to the north that is not a volcano, you could experience less snowfall and find locally lower hazard on Monday. Continue to check the bonding of the snow from over the weekend and be leery of areas where avalanches are more likely to be triggered such as wind-loaded terrain, convex rollovers, unsupported slopes, or near the base of cliffs.

    (12/19/2021)

    Using simple hand pits while you travel is a quick way to gain some information about slab potential and the depth of potential weak layers in the upper snowpack. 

    Photo: Dallas Glass

Avalanche Discussion

As is often the case in the West South, conditions are variable around the zone. While some areas received a relative break in the stormy weather on Sunday, all areas should be back to snow on Monday. The volcanoes and areas from White Pass southward are forecasted for the highest water amounts and are again driving the avalanche hazard. That doesn’t mean that hazard does not exist elsewhere. 

A new interface formed during Saturday’s warmup (12/18) should be a good snowpack marker throughout the zone for you to investigate for potential weakness. At lower elevations, this layer could be an ice crust due to rain or freezing rain. In areas such as Crystal, snow appears to be well bonded to this layer, but we do not have observations from many other locations of the zone. Therefore, we cannot speak confidently about the reactivity of this layer or the recent storm snow. You should be suspicious of all of the recent storm snow from the weekend as well as the newly fallen snow on Monday. Strong winds throughout the zone this weekend may also have built fresh cornices or created Wind Slabs that could now be shallowly buried by more recent snow. Take care in wind-prone areas by giving fresh cornices a wide berth and feeling for subtly stiffer snow under the surface. If you're out and about, we'd love to hear what you're seeing out there, so submit an observation.

At lower elevations, you could find that rain has reinvigorated open creeks or further enhanced early season hazards such as rocks, stumps, or punchy snow. Take care when traveling at these elevations and be on the lookout for further rain in the southern half of the zone by day’s end at the lowest elevations.

Regions covered