Bollettino valanghe

West Slopes North

Northwest Avalanche Center
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Pericolo valanghe

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

Wind drifted slabs of snow are where you are mostly likely to trigger an avalanche on Sunday. A mixture of newer, smaller drifts and thicker, more stubborn old drifts could both be a concern, especially as you gain elevation. Identify slightly heavier, wind-deposited snow and steer around these features on steep slopes.

Problemi valanghivi

  • Wind Slabs

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

    Wind events over the last several days produced a variety of wind-affected snow. Some areas were stripped, while some very hard deposits developed. Most of the stiff slabs were stubborn to unreactive on test slopes. A few pockets did produce easy, planar results with simple hand shear tests. Some even failed when isolating the column. The longer these slabs sit the more difficult it might be to trigger an avalanche on one of these slabs, but it is still possible that you could find a reactive one in steep terrain.  THIS observation from Saturday sums up much of what we've been seeing in recent days. 

    Older slabs have characteristic smooth, rounded features and nearby eroded, or stripped, surfaces.  A few inches of new snow is expected by the end of the day. A fresh coating will likely hide the older slabs, making it more difficult to identify where they are. By later in the day, shallower new soft slabs may develop. These may be located in the more common areas, such as along ridgelines, in gullies and on convex rolls, unlike the larger old slabs which developed in less common places with unusual winds. Paying attention to the feeling of snow beneath you is important during the day. Feeling for stiffer, hollow layers beneath you is a key area to avoid old slabs. As for the softer new slabs on top, pay attention to thicker new snow deposits and avoid these locations on steep slopes, especially if they begin amounting to 6 inches or more. One other important factor is that weaknesses developed on the snow surfaces in areas that weren't affected by wind over the last week. This could mean that newer, shallower, slabs could pop off easier than expected in sheltered areas. 

    (12/6/2022)

    Small pockets of new snow could release nearer to the end of the day Sunday.

    Photo: Dallas Glass

Avalanche Discussion

A variety of wind slabs could be found during your outing Sunday. Your challenge is identifying the different layers and avoiding them in areas where they could produce avalanches. A shallow, soft coating of surface snow could hide crusty, variable layers beneath. Wind-protected, shady slopes are where you might still find nice low-density snow, however, this is where surface hoar likely exists on the old snow surface and shallow new snow avalanches could easily be triggered. 

Buried surface hoar and deeper crust-facet layers still lurk in the middle and lower snowpack in some areas. No new avalanches related to either of these layers have been reported this week despite extensive backcountry traffic. Heavy loads might produce a large avalanche in any of these weaker layers. A big load of new snow or rain from a future storm might also wake up these layers and produce very large natural avalanches.

Regioni coperte