Lawinenlagebericht

East Slopes North

Northwest Avalanche Center
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Lawinengefahr

Mon
Hochgebirge
3 · Erheblich
Waldgrenze
3 · Erheblich
Unterhalb
2 · Mässig
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Kernpunkte

New snow with warming temperatures may overload our weak snowpack. You could easily trigger avalanches large enough to bury you in steep terrain, particularly on northern aspects or wind-drifted terrain below ridgelines or the base of cliffs. Avoid steep terrain and choose lower-angle, wind-sheltered slopes to enjoy the new snow. 

Lawinenprobleme

  • Storm Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Likely
    Größe
    1–2

    We expect widespread storm slab avalanches from the combination of snowfall with slightly warming temperatures and existing weak snow surfaces. Avoid steep slopes and likely trigger points, such as convex rolls. Northerly aspects and steep wind-loaded terrain are the most likely places for large avalanches. However, Lower elevations that stay cold below the inversion have a particularly weak snowpack, and previous snow surfaces are variable, so treat all steep terrain with suspicion. Shooting cracks, collapsing, or fresh avalanches are all red flags that the snow is unstable.

    Choosing simple, low-angle slopes for recreation will be key for a safe day out on Sunday. The variability in deeper weak layers and surfaces makes the sensitivity of triggering avalanches tricky to forecast. So, while you can make observations using test slopes and hand pits to observe how the new snow reacts, don't try to extrapolate your results to nearby slopes. It's better to wait until this storm tapers out and we gain more information about how our weak snowpack handles this new load. 

    (1/27/2021)

    An example of shooting cracks in recent storm snow, a clear indication of instability. 

    Photo: Drew Lovell

  • Persistent Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    2

    This storm may make triggering much larger persistent slab avalanches easier on northerly aspects. Give large avalanche paths some extra margins on Sunday, especially in steep rocky terrain or wind-loaded slopes below ridgelines or the base of cliffs.  Signs of instability, like avalanches, whumpfing collapses, or shooting cracks, are bullseye signs to steer well clear of steep slopes. 

    Over the last few days, there have been multiple reports of wind slab avalanches on the weak, faceted snow of the January Drought Layer (JDL). You can find facets from the January Drought Layer 1-2ft below the snow surface. Facets from early January and December, buried 2-3 feet deep under old stiff wind slabs, are more isolated. While these layers are less likely to be problematic, consider the consequences of triggering a much deeper avalanche. The distribution and reactivity of this problem are still uncertain, but with the additional snow, it's time to take a step back and let these tricky, persistent layers adjust to the new load.  

    (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

Snowfall and westerly winds picked up in the late afternoon on Saturday for the Washington Pass Area. This storm isn't packing much moisture, but we should see between 6-8 inches of snow. Temperatures should increase slightly, but we don't expect snow levels to climb above 2500ft on Sunday. Monday might bring some additional warming and a chance for mixed precipitation at the lowest elevations in our forecast area. We aren't sure if these modest precipitation amounts will be enough to tip our weak snowpack over the edge. But, with this uncertainty, it's best to step back into simple conservative terrain until we gain more information on how the new snow reacts. 

Lower elevations have a very weak, faceted snowpack since they stayed in the deep freeze below the inversion even as upper elevations warmed in January. On Saturday, an NWAC Forecaster found a thick layer of very weak, faceted snow below last week's storm slab. Previously, we haven't had enough of a slab for avalanches to be a concern at lower elevations, but Sunday could be a different story. So don't get caught off guard thinking that steep terrain in lower elevations might be safer.

On Friday, NWAC Observers in the Twisp River area noted increasing westerly winds and significant blowing snow along ridgelines. The snowpack in this area of the zone was shallow and faceted, but where they traveled at mid and lower elevations, the lack of an overlaying slab limited avalanche concerns. Further north, near Washington Pass, observers reported a large (size D2) natural avalanche resulting from a cornice fall on Feb.13th. They also reported a skier-triggered hard wind slab avalanche. Both were at upper elevations on northerly aspects and may have involved the January Drought Layer.  Since then, 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 a persistent slab. There are also reports of isolated, large, and very large avalanches that occurred during the storm at the beginning of February. We suspect these avalanches failed on the weak, faceted January Drought Layer (JDL).

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 is an example of where the mid-December facets were 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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