Avalanche forecast

East Slopes North

Northwest Avalanche Center
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Avalanche danger

Sat
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
2 · Moderate
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Highlights

We're transitioning from hot and sunny to more seasonable weather in the East North.  Wet avalanches will be possible until the snow surface has enough time to thoroughly freeze and stabilize. Make travel plans that minimize your exposure to wet surfaces and overhead cornices.

Avalanche problems

  • Wet Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    2–3

    The East North is in transition from a phase dominated by wet natural slabs toward a phase marked by lingering potential for human or cornice-triggered dry slabs on upper elevation northerly aspects. Unfortunately, temperatures are expected to be mild enough on Friday, that we think that wet slabs on aspects receiving the sun's energy will be the greatest threat on Friday. If you do find dry snow, consider digging down to the early February crust before exposing yourself to consequential terrain.

    Here are some tips to reduce your risk from wet avalanches: Watch for rollerballs and moist 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 slopes before they become wet and weak. Put a terrain buffer between your group and large start zones or complex avalanche paths above 6,500ft. Use extra caution when you find less than 5 feet of snow. Facets buried at the beginning of February exist over a crust 2-4 feet below the surface.

    Avalanches could vary in size and consequence. Loose wet avalanches may be small. 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 buried as much as 3 feet below the surface. The chances for large avalanches could increase by midday and afternoon if the surface crust breaks down.

    (3/15/2024)

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

    Photo: Willie Webster

Avalanche Discussion

The East North has finally enjoyed several nights with good refreezes at middle and upper elevations. From March 14th through 6 AM on March 20th, the Washington Pass Upper station remained above freezing with shallow refreezes on many aspects. Inversions created better refreezes in middle and lower-elevation valley locations. Thursday and Friday should be more typical of our April-May diurnal refreeze weather patterns. This should help the likelihood of avalanches decrease as the snow surface begins to freeze and stabilize from the top down. However, we're not exactly throwing the snowpack in the freezer, and Friday should be a touch warmer than Thursday. The potential for wet and shedding-style avalanches will continue until a stout surface crust has developed. Minor amounts of precipitation are unlikely to change the avalanche situation appreciably, and that is what we expect through Friday. However, if you find yourself in a moderate rain shower, assume that water will be flowing quickly into and potentially pooling on any remaining crusts, increasing the threat of a very large avalanche.

Since the 14th, observers reported natural wet avalanches on steep, sunny slopes up to size D2. The most recent large slab avalanche was reported on Sunday in Willow Creek, WNW, 7,200ft. This occurred on an unsupported slope, possibly due to snow shedding from overhead cliffs, and it likely ran on either a weak interface from March 9th or layers buried in February.

On the 16th, an NWAC observer got an aerial overview of recent avalanche activity and cataloged numerous large to very large slab and wet avalanches. We suspect many of these slab avalanches ran on the March 9th interface, while the deeper slides were likely on facets above the Jan 31st crust. Several small wind slab avalanches and numerous large to very large persistent slab avalanches were also noted in the second half of last week (see photos below).  From 3/9-12, the Harts Pass Snotel has picked up about 1.8" of water, all falling as snow at mid and upper elevations. On March 5th, forecasters visited the site of a remotely triggered (D3) avalanche on Kangaroo Ridge, which ran on a layer of facets buried in mid-February, just above the Jan 31st crust. 

Be mindful of the potential for cornices to sag and fail on slopes overhead. When traveling on ridges, keep plenty of distance from the edge and ensure you're not traveling on overhung snow. Cornice falls are difficult to predict. They're a hazard in their own right, but they can also trigger avalanches on slopes below. Avoid lingering underneath these behemoths; they're erratic and can fail at any time of the day, sometimes long after the height of warming. 

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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