Bollettino valanghe

West Slopes North

Northwest Avalanche Center
Vedi sulla mappa

Pericolo valanghe

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

In sintesi

It'll cool a bit Tuesday night, but temperatures hovering around freezing on Wednesday plus incoming precipitation means you could encounter wet or dry avalanche problems. In either case, there's a lot of uncertainty with avalanche conditions so stay off steep slopes. If you see natural avalanche activity or identify any other red flags, consider avoiding terrain beneath large slopes as well. 

Problemi valanghivi

  • Storm Slabs

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

    Human-triggered slab avalanches are likely at mid to upper elevations. Avalanche danger will increase as snowfall amounts grow throughout the day. We're forecasted to get about 6 inches of snow at higher elevations, but may get more in some areas of the zone.

    Most avalanche activity will probably be limited to newly fallen snow, less than a foot deep.   However, we've been in a fairly steady storm cycle since Saturday, and avalanches could happen in older storm layers, up to around 2 feet. Expect thicker slabs and more reactivity in wind-loaded areas. Obvious clues such as long shooting cracks from your weight, whumphing, or intense periods of snowfall and wind, are all strong indicators of instability in the snowpack.

    A lot of uncertainty exists with the current conditions, so remain conservative during your outing. This isn't a day to test steep slopes. Avoid all terrain greater than 35°.  If you identify any recent natural avalanches, steer around lower-angle terrain beneath steep slopes as well.  

     

    Example photo: Human triggered slab avalanches, like this one, are likely to occur on Wednesday. 

    Photo: Irene Henninger

  • Wet Slabs

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

    Natural wet loose avalanche activity up to size 2 (large) was reported in the Baker backcountry on Tuesday. We expect to see a slight cooling overnight which may freeze surfaces a little. Nevertheless, we still expect a variety of wet snow avalanche problems on Wednesday.

    Avalanches could range from shallow, wet loose in the new snow to ones that may be a little deeper, entraining the last few days' snow, especially as temperatures rise. Wet slab avalanches could also occur, failing up to a couple of feet deep. Glide avalanches may occur on steep, smooth rock faces. Avoid travel beneath large gaping cracks in the snow. 

    If you travel onto steep slopes, and if the snow is wet and sticky, you'll probably be able to trigger a loose avalanche. Wet slabs tend to release at unexpected times naturally, or may be triggered by a smaller loose avalanche. As before, this is definitely a day to avoid slopes greater than 35°, but if you're sinking past your ankles in wet, heavy snow, or notice any natural avalanche activity, avoid travel beneath steep slopes also. 

    An example of a wet slab avalanche from a rain event a few winters ago. They are often found in unusual locations. It's also difficult to predict the timing of when they occur during a rain or warming event.

Avalanche Discussion

Lower elevations have already received so much rain that wet avalanche activity has lessened in these areas. Mid elevations are where the most flux exists, with variable near-freezing temperatures and a mix of dry snow and rain. You might encounter either wet or dry problems at mid elevations on Wednesday. 

Mt Baker Ski Area triggered a very large slab avalanche with explosives on Hemispheres, with a crown 4-5 feet deep on Tuesday. We don't have specifics on whether it was wet or dry at the failure plane or what layer it failed on. The avalanche may have failed in a weak layer above the 12/30 crust. This shows that there are still weak layers further down in the snowpack that we're aware of. It just takes a really, really big trigger to get one of these slabs moving, and is unlikely for a human to trigger. 

We've received very little information from the backcountry since the weekend, and our information is very limited, especially at upper elevations. Up high, you can expect to find some dry snow, much of which is probably wind-affected. Lower down, travel, no matter the form, is probably unpleasant in wet, sticky and punchy snow. Plan on making constant evaluations as you travel, and if in doubt, use lower-angle terrain to travel more conservatively in the backcountry. 

Regioni coperte