Bollettino valanghe

East Slopes North

Northwest Avalanche Center
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Pericolo valanghe

Mon
Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
1 · Debole
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Non aggiornato — questo bollettino è scaduto 4 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

New snow is slowly accumulating, and you could trigger freshly formed slabs at higher elevations. Check for instabilities at the new snow, old snow interface and in any area exposed to wind drifting. Increasing ridgetop winds may notably increase the danger in the alpine later in the day.

Problemi valanghivi

  • Wind Slabs

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

    Washington Pass picked up at least 6" of new snow on Saturday, and it should continue to slowly add up. Shifting winds should drift snow around at upper elevations, with increasing west winds later in the day. Look for deeper drifts and shooting cracks as you gain elevation. Red flags like shooting cracks or natural avalanches are clear signs to step back to lower angled and more sheltered terrain. Especially use caution on steep lee slopes up near ridgelines, large cliffs. You can also check to see how the new snow reacts with hand pits, skin track tests, and small test slopes.

    Aside from slabs, small loose wet avalanches could become possible at low elevations if temperatures warm up later in the day.

Avalanche Discussion

 Observers noted ski triggering a couple small slabs at upper elevations on Saturday. These were both from upper elevation northeast facing terrain near Kangaroo. NWAC observer Willie Webster was out in the Pasayten wilderness on Thursday and found a shallower snowpack vs the Washington Pass area but similar surface conditions, snowpack structures and generally low avalanche hazard. As we begin to slowly add new snow over old surfaces, we'll have to monitor how older interfaces begin to react to the change. We can expect avalanche danger to generally increase as more snow adds up into the week.

Prior to this pattern change, recent warm temperatures and sunshine on the 25th and 26th formed crusts formed on steep, sun-exposed slopes. On shaded slopes, the snow on the surface and directly above the MLK crust was beginning to facet and weaken. Some observers have reported propagating test results on this layer.  We've also been tracking a layer of buried surface hoar from January 5th. Near Washington Pass, it's around 2.5ft below the snow surface but shallowly buried in the easternmost portion of the zone. Snowpack tests indicate the potential for propagation above about 5,500ft or in eastern portions of the zone, where the overlying MLK crust is thin or not present. 

The snowpack near the eastern edge of the zone is more shallow, and you may find weak layers of snow more susceptible to triggering an avalanche. In the lower-elevation foothills, warm and wet conditions transformed previously weak, low-elevation snow into melt forms.  While we have little recent info here, we suspect weak layers are forming adjacent to crusts in the upper half of the snowpack.

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