Bulletin d’avalanche

East Slopes Central

Northwest Avalanche Center
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Danger d’avalanche

Sun
Alpin
2 · Modéré
Limite forestière
1 · Faible
Sous la limite
1 · Faible
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Périmé — ce bulletin a expiré 2 years ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

As new snow amounts increase above firm crusts, so does your avalanche risk. Steer around steep, wind-loaded slopes, particularly in the lee of exposed upper-elevation ridgelines. Sun breaks could also warm the recent snow, so watch for small, wet loose avalanches on sunny slopes. 

Problèmes avalancheux

  • Wind Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    1

    Wind slabs will be more reactive and should increase in size and distribution, but remain small on Saturday. The East Central zone has picked up around 2-6" of snow over the most recent crust, with only a touch more on the way. However, moderate W winds will redistribute that snow Friday night through Saturday forming fresh, reactive slabs.  Pay attention to actively blowing snow, slopes below fresh sharp cornices, and other signs of recent wind transport to identify problem areas. If ridgelines and windward slopes have been scoured to a crust, expect drifts up to a foot or locally deeper on lee slopes. Simple hand shears or slope tests on inconsequential wind-loaded terrain features can help you assess the bond to the crust and the cohesion of the slab. If you have a slab and it wants to move on that crust, assume you can trigger an avalanche on nearby wind-loaded slopes steeper than 35 degrees. In portions of the zone where average snow depths are 4" or deeper, it won't take much wind loading to get the slab to the 6" threshold for knocking you off your feet. In most areas, the small size of these slabs makes them most dangerous if they push you over a cliff or onto a steep, icy slope.  

    (2/23/2024)

    Shallow wind slab, similar to what you can expect in some areas on Saturday.

    Photo: Matt Primomo

Avalanche Discussion

Several rounds of snowfall brought totals to around 2-6" above the last major crust. Observations in the Stevens Pass area to our west suggested enough snow for transport and the potential for a mediocre bond with the firm crust.  

Precipitation decreases for most of the zone on Friday night, leaving expected storm totals above the crust in the 4-6" range for western and northern areas. Expect 1-4" above the 3000-4000 ft rain/snow further east. The crust burial date ranges from 4/4 in the east to early on 4/3 in the west. Avalanche entrainment is expected to be limited to the snow above this crust. 

Although we expect that winds and cloud cover will limit warming, don't forget the impact of even 15 minutes of strong spring sunshine on the recent snow. If the sun makes an appearance, rollerballs are your primary warning to shift from sun-exposed to shaded slopes as the risk of a wet avalanche rapidly increases. These will move efficiently, gaining steam on the crust. While they are unlikely to be large, they could bury you in a terrain trap such as a gully or a creek.

On Thursday, Katie Warren was in the Wenatchee Mountains and found a few inches of new snow over a supportable crust. Moderate winds were drifting the snow around, but this didn't result in any notable wind slab formation at mid-elevations. They found isolated pockets of shallow wind slabs at the upper elevations. 

Recent reports noted less snow at lower elevations than is typical for early April, so be prepared for some interesting and challenging travel conditions. Katie experienced slippery, icy trail conditions below 5000ft on Thursday in the Wenatchee Mountains. It might be worth packing traction devices for summer trail approaches to reach a more consistent snowpack at higher elevations or if you travel in wind-scoured areas.

Let us know what you see as you travel in the mountains by submitting a public observation here. 

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