Bollettino valanghe

West Slopes North

Northwest Avalanche Center
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Pericolo valanghe

Sun
Alta quota
3 · Marcato
Limite del bosco
3 · Marcato
Sotto il limite
2 · Moderato
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In sintesi

A low-density coating of snow around a foot and a half deep sits over a hard crust, and it could be easy for a human to trigger an avalanche running under or within the new snow layer on Saturday. Snow is expected to be most reactive in the morning, which could be on any steep slopes, but avalanches will likely be larger and more dangerous in wind-loaded areas. Avoid steep slopes, especially at the start of the day,  giving time to let the storm snow settle.

Problemi valanghivi

  • Storm Slabs

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

    Your primary avalanche concern is storm slab avalanches failing with a human trigger on steep slopes on Saturday. Earlier in the day, snow will likely be more reactive before it has a chance to adjust.  Avalanches could occur beneath the new snow layer, which will be around 1-2 feet deep. They could also fail within the storm layer,  closer to 6 inches deep. We expect many steep slopes could avalanche with a human trigger, although locations with wind-drifted snow will likely produce larger and more dangerous avalanches. Most avalanches will probably be small, but some, especially at higher elevations and with more wind-effect, could be large. 

    To start your day, avoid slopes steeper than 35°. Evaluate the new snow/old snow interface and storm layers for bonding, and use small test slopes. If you identify layers that slide or any other signs of instability like recent avalanches, whumphing, or long, shooting cracks stay off steep slopes. Steer around steep slopes where you identify thicker wind-drifted deposits all day. 

    (3/14/2023)

    A D1.5 human triggered avalanche which occurred just after the last storm, before this past week's warming on the south side of Baker. Similar avalanches could occur, but we expect more of them, on Saturday.  ~45cm. W, 5800'

    Photo: Irene Henninger

Avalanche Discussion

On Friday we received reports from the Baker backcountry area that earlier in the day the storm layer was reactive and avalanches were running on the crust. Later on, most avalanches were failing within the new snow layer, 4-6" deep. Meanwhile at Canyon Creek, snowmobilers were reporting storm slabs failing 14" deep on the crust on most steep rollovers, which happened later in the day as the layer became more "slabby". This is a clear difference in characteristics depending upon location, which you can expect to see on Saturday as well.  There will probably be around a foot and a half of low-density snow coating the crust on Saturday. The last burst, with a few inches forecasted, is Friday night. If we get more or less snow than forecasted, the avalanche forecast may not be as accurate so be sure to evaluate conditions as you travel. 

A thick crust is present beneath the old snow surface in all areas aside from upper elevation northerly aspects. The only place you won't find that crust is the spots where you'll find a weak, faceted layer of snow that formed in those cold, shady, locations during our long period of high pressure in the last week. On those slopes, you may find even more reactive slab avalanches. You may be able to trigger small dry loose snow avalanches in non wind-affected areas on steep slopes. If the sun pokes out, which is most likely during the morning, small wet loose avalanches could occur as well. 

In the last week of primarily warm, sunny weather we've seen a constant trickle of wet loose avalanches, and an occasional larger slab avalanche or glide avalanche. Many of these wet snow problems have dissipated with the cold temperatures but not all yet. Continue to treat glide cracks and cornices warily, and avoid being anywhere near them. The old snow layer could be smooth or could be very bumpy, with old refrozen wet avalanche paths or debris piles hidden by the new snow. You'll likely find irregularities with your feet or sled, however, so travel very carefully. 

Regioni coperte