Lawinenlagebericht

West Slopes South

Northwest Avalanche Center
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Lawinengefahr

Sun
Hochgebirge
2 · Mässig
Waldgrenze
2 · Mässig
Unterhalb
1 · Gering
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Kernpunkte

Avalanche potential should increase throughout the day as springtime weather attempts to destabilize the upper snowpack. The amount of weak and wet snow available for avalanches at any given time will vary across the zone and with the weather. If you see signs of recent wet avalanches or find that the snow is wet and heavy, you should put these slides on your radar on slopes over 35 degrees.

Lawinenprobleme

  • Loose Wet

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    1–1.5

    Springtime weather should have you thinking about the possibility of Wet Loose avalanches on Saturday. Rising temperatures throughout the day and the threat of some new precipitation could combine to destabilize the snow surface. Those same weather inputs could help cornices sag and fail, possibly triggering slabs or loose avalanches on the slopes below. If you notice that the snow surface has become wet and sticky, take a moment to step off your mode of travel and see how far you are plunging into the snow. If you are sinking in past your ankle, you’ll know the snow has reached the threshold for Wet Loose avalanches. As you travel, look for visual clues such as fresh rollerballs and pinwheels to let you know the snowpack is getting unsettled and these slides are becoming more likely. These avalanches often start at a point and fan out as they descend, entraining snow and growing in size. When the snowpack has reached a point where Wet Loose avalanches are possible, you should steer around open slopes over 35 degrees and give overhead hazards such as cornices plenty of space.

    (3/25/2022)

    It's that time of the year when all aspects are suspect. Even northerly facing slopes like this one at White Pass couldn't escape the springtime weather and produced small wet avalanches. [NE 6600']

    Photo: Dallas Glass

Avalanche Discussion

On Friday, a strong overnight freeze from the night prior was reported at White Pass before surfaces softened throughout the day due to filtered sunshine. At least one natural wet avalanche was observed in the White Pass backcountry during the mid-day hours and evidence of recent avalanche cycles was easy to spot throughout the area. Similar conditions were reported by NWAC forecasters on Mount St. Helens on Thursday when firm surfaces eventually softened due to springtime temperatures. 

Add this up and that makes two nights in a row where a solid freeze helped stabilize the snowpack from the top down and kept avalanche potential muted first thing in the morning. With elevated freezing levels expected on Friday night, you may find a poorer overnight freeze has occurred when you step out of your car on Saturday morning. Despite this fact, we still expect that a crust should exist on the surface in many locations in the morning before daytime warming helps it soften. Wet and generally weak snow should be found on the surface in most locations by day’s end, but the depth of this layer will vary depending on aspect, elevation, and weather inputs. At this time of the year, not even northerly facing slopes will be able to escape the warmth to hold cold dry snow.

The newly forming surface crust should continue to thicken with each freeze/thaw cycle we have over the foreseeable future. Its strength will vary depending on temperatures and liquid input, but generally speaking, it should help to bridge any potential weak layers deeper in the snowpack. This includes the 3/8 facets that are sitting above the Early March Crust around 3 feet below the surface. Although not out of the question, we believe that an avalanche on this layer is unlikely at this point. The weak snowpack structure still exists, but has not produced any known avalanches in a week, has shown improving test results, and has a stronger snow structure above it. Any potential slide on these weak grains should need a very large trigger such as a cornice collapse in just the right spot. Elsewhere in the upper snowpack, you should find a mix of large polycrystals, crusts, and rounded grains. We do not have any concerns lower than the Early March Crust at this time. 

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