Bollettino valanghe

Stevens Pass

Northwest Avalanche Center
Vedi sulla mappa

Pericolo valanghe

Tue
Alta quota
3 · Marcato
Limite del bosco
3 · Marcato
Sotto il limite
2 · Moderato
Open full map
Non aggiornato — questo bollettino è scaduto 2 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

Significant new snow and wind, along with a layered snowpack, is a perfect setup for human-triggered avalanches. Slides could be larger and particularly dangerous where the wind drifted snow deeper. Find sheltered, low-angle terrain for recreation and avoid steep slopes or large convex features where you are likely to trigger an avalanche. 

Problemi valanghivi

  • Storm Slabs

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

    Another day, another significant storm with heavy snowfall and winds overnight. Choose conservative terrain and pay close attention to red flag signs of instability, such as recent avalanches, cracking, or collapsing. Avoid slopes over 35° and large convex terrain features, all likely places to trigger an avalanche. You could also trigger larger, more dangerous wind slab avalanches on lee slopes below ridgelines. Identify wind-affected snow using cornice formations, hollow-sounding drifts, or textured surfaces. Choose slopes below 30° in wind-loaded terrain or travel on wind-ward or scoured surfaces. 

    While cooler temperatures should help, the snowpack has a few concerning interfaces buried 2-3 feet deep. So, while most avalanches will involve just the overnight snow, there is a chance you could trigger a much deeper avalanche on one of these layers from earlier in the week. Small features and quick handpit tests can be a great way to observe how easily the snow slides. But your safest option is to choose conservative terrain on Monday and avoid stepping out onto steep slopes until this parade of storms ends and the snowpack has time to adjust. 

    A skier triggered an avalanche (D1.5) from outside the Stevens Pass Ski Area earlier this week. NE, 5,400ft.

    Photo: Adam Butterfield

Avalanche Discussion

A Puget Sound Convergence Zone might favor Stevens Pass on Sunday night. Convergence zones always come with a lot of uncertainty, so if it shifts further north or south, we could get significantly more or less than the anticipated 8-12 inches of snow. Regardless, a big takeaway from this ongoing parade of storms is that their frequency, duration, and fluctuating temperatures have limited the distribution of our observations and prevented the snowpack from adjusting before the next storm rolls through. This leaves us with significant uncertainty at upper elevations and a layered, variable snowpack at mid- and lower elevations. 

On Saturday, many backcountry users reported sensitive shallow slab avalanches in the new snow. While most of these storm instabilities appear to resolve after a couple of days, a weak layer buried on the 22nds is one to watch. You can find it 2-3 feet below the surface, just above the thick Solstice Crust. This layer was the culprit in a few larger avalanches triggered by Stevens Pass patrol on the 26th and backcountry skiers on the 24th on Rooster Comb and Lake Susan Jane outside the Stevens Pass Ski area. I was in the Henry Creek area on Saturday (12/28), and this layer still produced unstable test results at 4100ft. While the interface consists primarily of decomposing stellars (snowflakes) some profiles have revealed small faceted grains.

The snowpack was saturated at elevations below 3800ft, and the surface is littered with rain runnels. Cooling temperatures might mean we'll have a stout crust at lower elevations, with just Sunday nights new snow above it. Above this, 2-5 feet of snow rests over the Solstice Crust, depending on your elevation and proximity to the Crest. At 4100ft in the Henry Creek Drainage, I found 2.5 feet of snow over the Solstice Crust and an average snowpack height of 5 feet. The Friday warmup created a new melt-freeze crust below Saturday's new snow, 4-5 inches in this location. 

If you're in the mountains, let us know what you see by submitting an observation.

Regioni coperte