Bulletin d’avalanche

West Slopes South

Northwest Avalanche Center
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Danger d’avalanche

Mon
Alpin
3 · Marqué
Limite forestière
3 · Marqué
Sous la limite
2 · Modéré
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Points saillants

Stormy weather on Sunday will mark a return to both winter and dangerous avalanche conditions. Avalanches will be more likely on slopes over 35 degrees or during periods of heavy precipitation and wind. Ease into terrain slowly, looking for red flag signs of instability such as shooting cracks or recent avalanches.

Problèmes avalancheux

  • Storm Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely
    Taille
    1–2

    The West South should see the bulk of this storm during the daylight hours on Sunday, with snow expected to fall throughout the day. We are expecting over a foot of new snow on the volcanoes and slightly less than a foot closer to the crest during the forecast period. These accumulations will help develop Storm Slabs at all elevations throughout the zone. With the addition of significant winds, Wind Slabs will also develop in wind-prone areas or thicken existing slabs near and above treeline. You can look for blowing snow, fresh cornices, or large pillow-like piles to help you identify where these thicker and possibly stiffer slabs have developed. We are lumping these together because the core message is that it will be a stormy day and your terrain management should be similar between the two problems.

    Throughout your travels, be sure you are digging down to the Valentine’s Day Crust with your hand or shovel to check the bonding of all of the new snow. At the base of the storm snow, you may find a thin melt-freeze crust in some locations. Using small test slopes is an excellent way to see how the new snow is reacting to your weight. If you notice that the snow is failing in blocks (slabs) during your tests or that there are shooting cracks as you travel, dial back your terrain choices to avoid slopes over 35 degrees where avalanches are more likely.

    (2/18/2022)

    Hand pits consistently failed just above Valentine's Day crust around Paradise on Friday. Track this layer closely as the slab above thickens with incoming snow over the weekend. 

    Photo: Andy Harrington

Avalanche Discussion

This drastic pattern change should have you easing into terrain slowly and collecting information. The new snow and strong winds will be building slabs over a variety of existing surfaces, which could mean that the bonding is different throughout the zone and even from slope to slope. Recent reports from NWAC forecasters at Paradise and White Pass confirm that weak snow still exists around both the Valentine’s Day and Late January Crusts, further complicating matters. Avalanche Professionals in the Crystal area have confirmed similar conditions. Although the depth and stoutness of the February crust varies by location and aspect, generally speaking, you should use this as your baseline for all snowpack tests. We don’t expect widespread avalanche activity at either of these interfaces on Sunday, but we wouldn't be surprised to hear of some isolated issues. Keep an eye out for avalanches failing on these deeper layers or that are breaking widely and connecting terrain features. If you notice these persistent-type slides occurring, step your terrain choices way back. 

On the volcanoes, more precipitation is expected than closer to the crest. This means that any potential avalanche could be larger. It also means that they may be more sensitive. If you are recreating in these areas and see widespread natural avalanches occurring, know that the avalanche hazard may be elevated and you should consider minimizing your exposure to avalanche terrain. This advice is obviously applicable regardless of your location and natural avalanches will be more likely during periods of heavy precipitation and wind.

Unfortunately, the recent warm and sunny weather wreaked havoc on our snowpack in many areas and helped expose hazards such as rocks, stumps, and streams that are normally buried this time of year. The new snow should help to reestablish our mid-winter snowpack, but these objects may be lurking just under the surface. Take care while traveling not to get tripped up by one of these obstacles.

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