Avalanche forecast

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Northwest Avalanche Center
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Avalanche danger

Thu
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
1 · Low
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Highlights

Continued winds will maintain the potential for triggering shallow avalanches in wind-drifted snow, particularly at upper elevations. On northern aspects, there is a chance that you or a small avalanche could trigger a much larger slide on deeply buried weak layers. Consider steering around steep slopes with stiff wind-drifted snow below corniced ridgelines and the base of cliffs. 

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–1.5

    In a bit of a rinse and repeat of Monday, continued easterly winds will build wind slabs on lee aspects. We expect these fresh slabs to be shallow and confined to the usual terrain features like steep slopes below ridgelines, confined rocky chutes, and the base of cliffs. On southerly aspects, these avalanches will likely be more predictable and fail on melt-freeze crusts below the recent snow. More uncertain is the low likelihood but high-consequence possibility of wind slabs on northerly aspects stepping down into persistent weak layers, propagating widely, and becoming larger and more dangerous.

    Identify wind-loaded slopes using visual clues such as cornice formations or textured surfaces and feel for stiff over weak snow. You can also use small, inconsequential test slopes to observe how the snow reacts. Cracking or mini avalanches on test slopes are a sign you should avoid steep wind-loaded slopes. An observer on Feb. 9th triggered a small wind slab and was caught and carried on a southeast aspect that failed on a melt-freeze crust. Thankfully, no one was injured in the incident. 

    (2/9/2025)

    A small skier-triggered wind slab in the Cutthroat Drainage caught and carried a skier without injuries. 

    SE, 7100ft, SS-AS-R1-D1

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    2–2.5

    We expect the most likely place to trigger a large persistent slab will be on northerly aspects in wind-drifted locations below ridgelines or the base of cliffs and steep terrain with exposed rocks where the snowpack tends to be shallower.  You can find the January Drought Layer 1-2ft below the snow surface if you dig down and feel for stiffer, 4-finger, snow over surgery, weak facets. Where you identify this weak snowpack structure, consider avoiding steep terrain, especially if you find more than a few inches of stiff wind-drifted snow over this persistent weak layer. Signs of instability, like avalanches, whumpfing collapses, or shooting cracks, are bullseye signs to avoid steep slopes and keep more significant safety margins between you and large avalanche paths.

    We can't be sure how much the winds will increase the likelihood of this persistent slab problem. But it will likely notch it up to some degree, and it might not take much to increase the reactivity of persistent slab avalanches on this weak snowpack. Sometimes, small weather inputs such as moderate wind drifting can significantly impact stability in these situations. 

    Facets from December, buried 2-3 feet deep under old stiff wind slabs, are more isolated and unlikely. However, be aware of the potential consequences of a surprisingly deep avalanche, particularly in rocky, wind-affected terrain with an unusually shallow snowpack above 6500ft.

    (2/7/2025)

    A natural avalanche that likely ran on the 4-5th. The wide propagation suggests that it could have ran on the January Drought Layer. 

    Photo: Katie Warren

Avalanche Discussion

We will keep those northeasterly winds for another day on Wednesday, so don't put away the thick base layers and jackets just yet because the wind chill values will remain well below zero. These temperatures also mean that seemingly minor injuries, avalanches, or equipment malfunctions can quickly become life-threatening. The last few days of sunny, cold weather have increased the likelihood of loose dry avalanches in steep terrain and formed a thin, breakable melt-freeze crust on southern aspects at mid- and lower elevations. 

Over the last 48hrs, multiple human-triggered and natural wind slabs have been reported. While most of these avalanches have been relatively small, one was reported to have surprisingly wide propagation, indicative of persistent weak layers being involved. As backcountry users venture out into more remote areas of the zone, there are also growing reports of large and very large avalanches that occurred during the storm at the beginning of February. We suspect these avalanche failed on the weak, faceted January Drought Layer (JDL). While the weak layer and snowpack are widely variable, there is some consistency in the avalanche activity, and most occurred below cliff bands or in steep, unsupported, wind-loaded terrain. We still have quite a lot of uncertainty regarding the distribution of the weakest snowpack, but it seems clear this is the type of terrain to avoid. You can also dig snowpits and use sudden or propagating tests to identify the problematic structure and avoid steep slopes where you find it. 

An NWAC forecaster, observers, and other professionals in the Washington Pass area have found substantial evidence of weak snowpack structure throughout the zone. The early February storm brought 1-2 feet of snow to the zone that fell on either the JDL persistent weak layer or wind-stiffened snow over the JDL. In snowpack tests, the latter structure seems to be more problematic. Another complicating factor is that storm snow totals and total snow depths vary widely. Unfortunately, a likely pattern to the distribution remains elusive. We just can't quite align our snowpack observations with the observed avalanche activity. So we expect there are pockets of even weaker snowpack structure that we just haven't found in snow profiles yet, potentially because it exists in terrain we are still unwilling to venture into because of the avalanche hazard.  The JDL exists at lower elevations. However, it doesn't seem to be a current issue for triggering persistent slab avalanches since the overlying snow lacks cohesion or "slab" characteristics in many places. 

Less likely, but still a concern, are deeper layers of facets buried by older wind-drifted slabs during mid-December through mid-January. The distribution of this layering is more cryptic and complex but has been observed between 6,500-7,500ft in moderately wind-exposed terrain. An avalanche triggered on 2/1 near Cedar Creek/ Snagtooth Ridge shows an isolated area where this layer of mid-December facets was problematic. There are also slopes where you won't find the facets as they were melted or capped by a crust (high elevation rain event on Dec 7th) or blown away. 

You can help us gather more data by submitting an observation HERE or via the Avy App. 

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