Bollettino valanghe

West Slopes North

Northwest Avalanche Center
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Pericolo valanghe

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

Temperatures are cooling and it'll be snowing all day, shifting our avalanche problem mindset back to dry snow problems. Avoid steep wind-drifted slopes on Tuesday, as upper elevation slabs can grow deep along ridgelines and around features, possibly avalanching with a human trigger. Remain aware of where you're traveling, as there's a very small chance glide avalanches could release from glide cracks during the cooldown and it's not wise to linger beneath these features. 

Problemi valanghivi

  • Wind Slabs

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

    Size and reactivity of wind slab avalanches could differ depending on where you are in the zone and how much snow we get. Forecasted water amounts are all over the place, but there could be a foot or more of snow near and above treeline by the end of the day. Danger is expected to increase as the day progresses. Moderate to strong winds will redistribute snow into drifts which could avalanche with a human trigger. Search out fresh drifts which you can expect to see in the usual locations on or below ridgelines, on convex rolls, and around features. Avoid these locations on steep slopes. Search for obvious clues like long shooting cracks as indicators to avoid nearby slopes greater than 35. 

    The new snow may bond well to the underlying heavier and more moist snow. You're most likely to trigger an avalanche within the new snow layer, probably less than a foot deep. However, if you do make it above about 6000ft, a lot of snow fell during this storm and there is a very small chance a deeper avalanche could release, although this is unlikely. 

     

    An old photo of a small skier triggered wind slab in Canyon Creek. This occurred on a steep roll, which is similar to what you might encounter on Tuesday. 

    Photo: Greyson Herdman

Avalanche Discussion

Old wet avalanche activity was observed by NWAC Forecaster Lee, who went to the Baker backcountry on Monday. Most activity likely occurred on Sunday, with D2 -2.5 wet slab avalanches, although not an abundance of them.  By Monday the snow appeared to have been handling the water well, and wet snow avalanche activity was on the downward trend as temperatures began cooling slightly. Lee found a supportable snowpack on skis, sinking only a few inches into the snow, but when he stepped off his skis he still sank down to his thighs. He didn't see as much glide avalanche activity as we sometimes see during warm, wet events, which was likely due to a few previous warming events having already affected the snowpack in the usual glide crack locations. Keep glide avalanche concerns on your radar, however, and travel hastily or avoid slopes beneath glide cracks during your outing on Tuesday. Despite cooling temperatures, an insulating layer of new snow and residual heat and moisture in the snowpack is expected to keep the snowpack moist and softer for a few days. A crust may form on the surface of the old snow layer, something to keep in mind for your outing on Tuesday. 

As of Monday night, storm totals reached 7 inches of water at Heather Meadows, much of which has fallen as rain since Thursday. Snowlines mainly hovered in the 4000-5500ft range. This may seem like a lot of water for this relatively modest atmospheric river, but in general, the snowpack has handled the water quite well, with fewer large avalanches than we expected we'd see. Above 6000ft or so, there is likely several feet of snow from this system. Winds gusting extreme on Sunday likely redistributed a lot of this snow into very thick slabs. The "warm" temperatures up high likely kept slabs stubborn and not as reactive as it might be if the snow was cooler, low-density powder. There also have been very limited observations and once the storm slows down we may find more avalanches occurred than we thought. Areas closest to Mt Baker likely received the most precipitation, and in locations more distant probably only about half the amount of water fell, resulting in less avalanche activity as well. 

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