Bollettino valanghe

West Slopes North

Northwest Avalanche Center
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Pericolo valanghe

Sat
Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
1 · Debole
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In sintesi

You could find wet avalanches on all aspects with higher danger on sun-exposed slopes. Minimize travel on and under steep terrain where you observe the initial signs of wet avalanche activity. Identify and evaluate recently wind loaded slopes above treeline.

Problemi valanghivi

  • Loose Wet

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1–1.5

    Clearer skies and more sun Friday could increase the chance of seeing or triggering a wet loose avalanche. Though clouds will build throughout the day - along with periods of moderate snowfall in some areas -  strong sun should initiate wet avalanche activity in new snow that accumulated in the last few days. Take note of warming and wetting at the snow surface or if previously supportable crusts begin to melt and break down. If you observe signs of instability like rollerballs, pinwheels, or very small avalanches then consider limiting your exposure to similar terrain. Be on the lookout for wet avalanches on any aspect given the high angle of the sun or possible greehousing on northerly slopes. If there are more clouds than forecast or a frozen crust tops the snow surface then wet loose avalanches are unlikely.

    Small wet loose avalanche on a northerly slope near treeline. Was likely triggered by warming on April 19th.

    Photo: Adam Ü 

  • Wind Slabs

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

    A new crop of slabs was likely built by gusty winds and light snowfall. Though warm temperatures at treeline limited wind slab development, look for drier snow and more reactive slabs in alpine terrain. Pay attention to the pattern of wind loading as you gain elevation. Filled in tracks, scoured snow surfaces, cornice-like features, changes in snow texture - use these and other clues to suss out where wind slabs could be hiding. Evaluate the bond of wind slabs before committing to steep terrain - or just steer around wind loaded features to reduce the risk of triggering an avalanche.

    (4/20/2022)

    Human triggered wind slab avalanche on Grouse Ridge on Mt. Baker. Northwest aspect at 5800'.

    Photo: Patrick Kennedy

Avalanche Discussion

Thursday brought light precipitation at mild temperatures and gusty winds to the zone. Though only a few inches of new snow accumulated at treeline, expect to see more in alpine terrain. After a day of good snow conditions and sun, few ventured into the mountains given the dismal forecast. Limited observations noted a few inches of wet new snow near treeline with stubborn to trigger wet loose in very steep terrain.  Though mostly small, wet loose avalanches were gouging into deeper snow layers.

On Wednesday observers in West North reported skier and snowmobile triggered shallow slab avalanches in terrain steeper than 40 degrees. It’s likely that a period of warming in the morning increased slab reactivity, even on northerly terrain. Small wet loose avalanches were observed on most aspects before skies clouded over in the afternoon. Expect to find a crust on temperature and sun affected snow surfaces. Extensive wind transport was noted on the higher peaks with less below 5500'.

There are no new reports of avalanches releasing in a layer of surface hoar that was buried last weekend. That being said surface hoar is responsible for at least one avalanche this week and probably a few more where the weak layer was not visibly confirmed. Though not cause for alarm, the possibility of a surprising avalanche that releases above you or remotely should still factor into your terrain choice on northerly slopes at treeline and above.  If you were to find buried surface hoar it would be on northerly, mid and upper elevation slopes where it managed to survive sun, warmer temperatures, and wind.

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