Bollettino valanghe

East Slopes South

Northwest Avalanche Center
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Pericolo valanghe

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

In sintesi

Sunday will not be the day to let your guard down. Triggering a large avalanche remains likely on steep, open slopes above 35 degrees.  Let the snowpack heal by traveling on lower-angle terrain and limiting your overhead exposure. 

 

Problemi valanghivi

  • Storm Slabs

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

    After 12 + inches of new snow (1+ in swe) in the last 24 hrs, slabs will continue to be reactive, especially in areas where weak surface snow (surface hoar) was buried.  Any steep, open slope may harbor this surface hoar, so using conservative terrain selection will be critical.  Avoid traveling on and under slopes greater than 35 degrees until this new snow settles and we learn more about the distribution of this recently buried weak layer.  Larger slabs will develop at higher elevations where winds will deposit new snow into fresh drifts.  Use hand pits or test slopes to evaluate how the new snow bonds to the old surface.  Steer around slopes if you observe test slopes sliding easily, cracking within the new snow, or hard over soft layering.

Avalanche Discussion

The East-South exceeded precipitation amounts for this storm, with Green Lake and Lost Horse SNOTELS recording over 1.5 inches of precipitation.  This likely translated to 1-2 ft of new snow, which is a significant new load for the current snowpack. 

Leading up to this storm, the east-south zone had some cold and clear nights that may have developed weak surface snow ( surface hoar and near-surface facets).  Adjacent zones to the north, south, and west have observed this weak surface snow. So it's possible that its distribution extends into the east-south.  A thin gray line will often indicate a layer of buried surface hoar. So if you see this thin gray line, avoid slopes on similar aspects and elevations 

Higher elevation areas such as Mt. Aix and Darland Mtn have a deeper and more layered snowpack.  In these locations look for weak, sugary snow that sits adjacent to a crust buried in late November.  There have been limited observations of recent avalanche activity on this layer in this zone.  However, our neighbors to the north in the east-central zone have observed avalanche activity on this 11/22 layer and are still receiving propagating results in test pits.  As of Saturday, the Mission Ridge Pro Patrol triggered large avalanches in wind drifted snow  during control work. Some of these avalanches were quite deep (1-3ft) and some likely failed on the 11/22 layer. 

The combination of limited observations and knowing adjacent zones are dealing with a poor snowpack structure, should make you take a step back and closely evaluate shaded slopes that may harbor this weak snow.  

If you get out into the East-South Zone tell us what you see by submitting an observation on our public observation platform!  These observations play an integral role in producing a quality avalanche forecast, but also help the greater backcountry community.

Regioni coperte