Bollettino valanghe

East Slopes North

Northwest Avalanche Center
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Pericolo valanghe

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

Dangerous avalanche conditions will continue during a prolonged warm-up.  Stay well out of and away from complex terrain as the day warms.  Shallow avalanches may step down to deeper weaker layers, creating much larger and more powerful avalanches that can travel to lower elevations. 

Problemi valanghivi

  • Wet Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Likely
    Dimensione
    2–3

    Watch for rollerballs and wet snow as signs that you could soon see wet avalanches. You can avoid triggering avalanches by moving to more shaded or lower-angle slopes. Time your travel to be off of slopes before they become wet and weak.

    Avalanches could vary in size and consequence; Loose wet avalanches may be small in the morning.  As slopes continue to warm, they could gouge deeply, becoming large and dangerous.  Wet slab avalanches could occur in the recent snow in the top foot of the snowpack, or they could break widely across large terrain features on weak layers from February in the top 3 feet of the snowpack. The chances for large avalanches will increase by midday and afternoon.

    Several large to very large natural avalanches were reported on persistent weak layers in the past couple of days.  With warming and meltwater entering the snowpack, we could see this trend continue. Put a buffer of terrain between your group and large start zones or complex avalanche paths above 6,500ft. Use extra caution in areas where you find less than 5 feet of snow on the ground. Facets buried throughout February exist over a crust in the top 2-4 feet of the snowpack.

    (3/15/2024)

    Recent widely propogating avalanches on a ridge between Tower Mountain and the Needles. E aspect at 7000'

    Photo: Willie Webster

  • Cornices

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1.5–2.5

    Be aware of falling and overhead cornice hazards. When traveling on ridges, keep plenty of distance from the edge and be sure that you're traveling on the part of the mountain and not on overhung snow.

    Cornices falls are difficult to predict, tho they typically happen with warming temperatures and sun. They're a hazard in their own right, but they can also trigger avalanches on slopes below. Avoid lingering underneath these behemoths, especially as the day warms. Sometimes, they can fall well after the warmest time of day. 

    (4/4/2023)

    An example of cornices near Blue Lake and Stiletto Peak from a previous season.

    Photo: Willie Webster

Avalanche Discussion

It's been an active few days in the Washington Pass corridor. On the 14th and 15th, observers reported natural wet avalanches on steep, sunny slopes. An NWAC observer got an aerial overview of recent avalanche activity and cataloged numerous large to very large slab and wet avalanches. Several small wind slab avalanches were also noted in the second half of the week. There have been numerous reports of large to very large persistent slab avalanches since the 10th (see photos below). on 3/12, multiple parties reported a large natural avalanche in the Cutthroat drainage that ran approximately 1500'.  This may have been a smaller avalanche that released from cliffs and triggered a larger persistent slab on the slopes below.  From 3/9-12, the Harts Pass Snotel has picked up about 1.8" of water, with all of that falling as snow at mid and upper elevations.  

On March 5th, forecasters visited the site of a remotely triggered (D3) avalanche on Kangaroo Ridge. They found that the avalanche was ~2.5-3 feet deep and ran on a layer of facets buried in mid-February, just above the Jan 31st crust. Tests still produced sudden or propagating results indicating that backcountry travelers could trigger similar avalanches, especially in areas of relatively shallow snowpack. There have been multiple reports of close calls, natural avalanches, and snowpack observations in the Highway 20 corridor that point to the deep, persistent slab problem. Widespread, very large natural avalanches occurred between February 28th and March 3rd. 

Snowpack information is limited outside of the Highway 20 corridor and Harts Pass. Let us know what you find if you get out into the backcountry!

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