Bollettino valanghe

East Slopes South

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

A shot of new snow and strong winds will build stiff slabs on downwind slopes. Avoid travel in steep terrain where you observe smooth drifts of wind transported snow. This will reduce the risk of triggering an avalanche until the new slabs have time to bond to the layers below.

Problemi valanghivi

  • Wind Slabs

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

    Very strong winds and 3-6” of new snow should create a fresh batch of dense wind slabs. These are commonly found on leeward slopes below ridgelines but Sunday you may also see them farther downslope than normal. They could even be found in a few below treeline areas that still have enough snow cover to produce avalanches. 

    The storm will back off Sunday and active wind loading should taper.  In the absence of blowing snow use clues to figure out where the wind created new slabs. Eroded or scoured snow surfaces, fresh cornice features, and rimed trees can all show the wind loading pattern in the terrain around you. Stiff, smooth snow surrounded by rougher surfaces is probably wind slab. Upside-down snow is also a great sign that you have found a wind slab. Not great skiing or riding though . . . . 

    You may find deeper new snow, thicker slabs, and greater avalanche danger as you travel closer in the zone towards White or Chinook Passes.

    (12/3/2022)

    Shooting cracks like this are in-your-face indicators pointing at unstable snow. Move to lower angled and more sheltered slopes  if you see signs like this.  

    Photo: Dallas Glass

Avalanche Discussion

We will likely see clearing skies and sun on the east slopes of the Cascades tomorrow. Widespread wet loose activity is not expected but as usual, keep an eye on terrain overhead that is warming in the sun and producing rollers or very small loose wet avalanches.

The recent spell of sunny days and clear nights most likely left behind surface hoar and weak facets at the current snow surface. Though no observations of weak snow surfaces - or any other observations for that matter - have been reported from East South, weak snow surfaces were found throughout the CascadeRange on Thursday and Friday. 

If buried intact, the old snow surface would make for slabs that are easier to trigger or release in surprising ways. On the other hand, weak grains will likely be disturbed and damaged by strong winds prior to snowfall in most - but not all - locations. 

If moving into avalanche terrain in the coming days, the best policy would be to first identify and investigate the interface between new and older layers. At the very least take your time and ease into steeper terrain by starting with smaller, less consequential slopes. Finally, don’t ignore obvious signs of instability like whumphs, shooting cracks, or recent avalanches.

Chances are you will encounter challenging travel across the zone on a stout rain crust from mid-January found just below recent new snow. At lower elevations, you may find shallow conditions with many hidden hazards present, like exposed or barely covered rocks or stumps.  

If you get into the East-South, please let us know what you see by submitting a public observation! 

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