Bollettino valanghe

West Slopes South

Northwest Avalanche Center
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Pericolo valanghe

Sun
Alta quota
3 · Marcato
Limite del bosco
3 · Marcato
Sotto il limite
2 · Moderato
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In sintesi

Saturday will be a dangerous day in the mountains. New snow, wind, and a weak snowpack structure should result in reactive and potentially surprising avalanches. You should let the snowpack adjust to the new load by avoiding slopes over 35 degrees.

Problemi valanghivi

  • Storm Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Likely
    Dimensione
    1–2

    You are likely to trigger an avalanche on slopes over 35 degrees, particularly ones that are convex, unsupported, or wind-loaded. Over a foot of recent snow could exist over the 12/30 crust at middle and upper elevations, meaning the depth is there for large avalanches to occur. Some of these could break widely or in surprising ways by failing on buried weak snow grains. Take note of whumpfing collapses, shooting cracks, or recent avalanches as you travel. These red flag signs of instability indicate that the snowpack is unhappy and you should avoid slopes over 35 degrees. 

    In isolated locations, avalanches could step down to older layers, resulting in even larger slides.

    (1/5/2024)

    Shallow slabs failed near ridgelines, sliding on a firm layer below. Expect them to be much larger on Saturday.

    Photo: Andy Harrington

Avalanche Discussion

All the ingredients appear to be in place for slab avalanches to occur on Saturday - incoming new snow, wind, and a weak upper snowpack structure.

A parade of small storms this week has steadily increased avalanche potential. Storm totals around the zone vary greatly, but the volcanoes have outpaced the crest significantly. That pattern should continue Friday night and Saturday with Mount St. Helens and Mount Rainier once again in the bullseye. We are forecasting the highest avalanche hazard since our atmospheric river on December 10th. 

In most areas, snow will be sitting atop the 12/30 crust. NWAC has identified weak snow (buried surface hoar) above this crust near Crystal Mountain. It was propagating in large column tests on Friday. Recreationalists near White Pass reported similar results during snowpack tests on Thursday. Observations from other areas in the zone this week have been limited. The 12/30 crust may look a little different based on your location and elevation. It could be thin and friable or more stout. Once you identify it, use it as a baseline to focus your snowpack observations. You might find a thinner 1/4 crust before reaching the 12/30, depending on your elevation/location.

There are other potential weak points in the upper snowpack. We’ve been discussing them in more detail recently, including the Solstice Crust and 12/25. You can take a look back at this week’s forecasts to gain a better understanding of them. For Saturday, you should know they are down there; some have propagated in large column tests this week, and any could reach a tipping point this weekend. That could be by human triggers or, more likely, another avalanche stepping down.

We know that this is an exciting time for backcountry enthusiasts. We’ve all been starved for a cold and snowy weekend. Try to show some restraint. Saturday has the potential to be quite dangerous. It is not the time to jump into big terrain that has been off-limits all season.

This week's snow has helped improve travel conditions, and this next wave should continue that trend. That said, objects that were easy to spot, such as open creeks or boulders, are now barely hidden out of view . Continue to tread lightly out there, particularly at lower elevations.

We really need to hear what you’re seeing this weekend, whether there were avalanches or not. If you’re out and about, playing or taking a class, please submit an observation.

Regioni coperte