Bollettino valanghe

West Slopes Central

Northwest Avalanche Center
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Pericolo valanghe

Wed
Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
2 · Moderato
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In sintesi

Another warm sunny day will maintain concern for wet loose avalanches. Watch for changing conditions on sun-exposed slopes and move to shaded or lower angle terrain by the time snow surfaces become wet and unconsolidated. 

Problemi valanghivi

  • Loose Wet

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

    Tuesday will be the third day in a slow and ongoing wet loose avalanche cycle. Only the most northerly and shaded slopes will escape the effects of the strong April sun. The day will start out cold, but expect snow to begin melting off trees and rocks by mid-morning. Falling snow on slopes below may be first to initiate loose wet avalanches. The sun will work around the compass E-S-W as the day progresses, and wet loose avalanches could occur on any steep slopes in direct sun. 

    Pay attention to rapid changes in the snow surface and watch for rollerballs and avalanches on similar slopes. It's time to move to shady slopes or head home early when you start noticing these indicators. Keep your return routes in mind as well - slopes you crossed safely early in the day may become wet, weak, and dangerous by afternoon.  

    (4/9/2021) Recent large wet loose avalanches on steep southeast aspects on Lichtenberg in the Stevens Pass Zone.

  • Wind Slabs

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

    Snow from recent storms (4/7-8 and 4/9-10) continues to settle and is generally well bonded to an underlying crust (4/7 interface). Some concern for wind slabs lingers, but these slabs are a few days old and gaining strength. You may still find unstable areas of wind drifted snow above treeline, primarily on north and east aspects above 5000ft. The most likely places to trigger an avalanche would be on rollovers 35 degrees and steeper, and on slopes below cornices and cliff bands. Use visual clues to identify and avoid wind-loaded snow in consequential terrain. Seek out wind-sheltered slopes or terrain less than 35 degrees if you find recent avalanches, cracking, or collapsing. 

    (4/11/2021) A small snowmobile-triggered wind slab (D1) on an east aspect at 5000ft near Park Butte in the Mt. Baker NRA in the West North Zone.

Avalanche Discussion

More sun-exposed slopes will shed snow Tuesday, and a significant spring thaw will continue through the week. Freezing levels are on the rise (6500ft) and will climb each coming day. The wet loose cycle is underway, and plenty more slopes have yet to flush out. Expect a mix of wet and dry snow avalanche problems and big variations between aspects, elevations, and time of day. 

On Monday, observers in the West Central zone reported numerous small wet loose avalanches from the past two days in steep, sunny terrain. North facing slopes above 4000ft still held cold dry powder, and wind slabs appeared unreactive to triggers even high in the alpine. Isolated large glide avalanches occurred recently in adjacent zones, and we will likely see more with continued warming and sun. Keep your eyes peeled for crevasse-like cracks in the snowpack and avoid travel on or below slopes where they exist. Cornices grew large throughout the winter and continue to be tested by sun and warming. Stand far back from these features along ridges, and avoid travel on slopes below.

On Saturday, a skier triggered an avalanche in the Snoqualmie Pass zone and was caught, carried, and fully buried. Fortunately, the skier was rescued by their partner and survived, but sustained injuries during the event. You can read the Accident Summary or watch this Video for more information.

During the ongoing Covid-19 pandemic, continue to follow the latest guidance from local, state, and federal health officials. Avoid unnecessary risks that could impact first responders and stress medical resources.  Wear a mask when appropriate, practice social distancing, and consider recreating closer to home.

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