Avalanche forecast

West Slopes Central

Northwest Avalanche Center
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Avalanche danger

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Out of date — this forecast expired 3 years ago.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

Highlights

Warm temperatures and lots of dry snow mean there is still a risk of triggering or being overrun by a wet avalanche. Avoid being on or under steep slopes where you see signs of instability like rollerballs, pinwheels, and recent avalanches. Stay out from under drooping cornices or cliffs shedding snow.

Avalanche problems

  • Loose Wet

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

    Rain showers should taper off, but warm temperatures and high snow levels will continue. When temperatures go up, some dry snow will inevitably come down. If you see a wet avalanche or other signs of instability, then expect to see more. Loose snow avalanches are the kind you are most likely to see. They often initiate from steep treed or cliffy terrain.  Also, look out for sagging cornices and blocks of snow sliding off of cliffs and rock slabs. Wet slab avalanches are also possible, especially if triggered by a smaller avalanche from above. Sunbreaks will accelerate warming and avalanche activity.

    (1/19/2024)

    Natural wet avalanche off the north side of Table Mt that initiated at about 4900'. This slope commonly produces avalanches during warming and rain events.

    Photo: Julz Holder - Grounding Truth

Avalanche Discussion

Slabs of dry, wind-drifted snow can still be found in the highest elevations. They are becoming more difficult to trigger, but you could still find one on steep convex breakovers or other unsupported features. Simple tests like slope cuts, skin track tests, and hand shears can help you get an idea of how unstable the new slabs might be.

The trickiest part of Saturday's forecast hinges on the difference between rain and warm temperatures and how they work separately - or together - to drive avalanche danger. In the simplest explanation of how it all works, liquid water is what basically makes dry snow unstable. Rain will nearly always drive more instability than temperatures alone. Warm temperatures have to melt the snow while rain just puts the water straight into the snowpack.

So with minimal rain for Saturday, it’s probably going to be a situation where warm temperatures won’t quite drive the quantity of instability seen today with rain. On the other hand, we will be at 36 hours of above-freezing temperatures by Saturday afternoon. Cornices and glide slabs that didn’t do much today could wake up with another 12-24 hours of the same conditions - and trigger bigger avalanches on the slopes below. So call it a lower likelihood for avalanches, but a higher consequence. 

About a half to three-quarters of an inch of light but steady rain fell in most parts of West Central on Friday. Temperatures at 5000' were well above freezing by the end of the day, and this trend will continue. While West Central saw temperatures grow ever milder, the Passes saw cold easterly flow and drastic temperature changes over short distances. Snow quality around Alpental was actually better at lower, colder elevations. Soggier snow was found the higher one climbed. While the Snoqualmie Pass stayed very cold, temperatures just a bit west hit 40F at 4500ft! Avalanche activity seemed to be limited to very shallow (4-6in) soft storm slabs on unsupported slopes. Numerous wet avalanches were reported from West North where warmer temperatures ruled the day.

 

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