Avalanche forecast

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Northwest Avalanche Center
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Avalanche danger

Thu
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
2 · Moderate
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Highlights

We're approaching the tail end of a long period of very warm weather.  Give the snowpack another day to cool before traveling on or under complex terrain. Time your travel to be off of slopes before they become wet and weak and don't linger under cornices.

Avalanche problems

  • Wet Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    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. Put a buffer of terrain between your group and large start zones and 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 2-4 feet below the surface.

    Avalanches could vary in size and consequence; Loose wet avalanches may be small in the morning. 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 that were buried a week ago or even deeper to the Jan 31st crust, over 3 feet below the surface. The chances for large avalanches could increase by midday and afternoon if enough sun makes it through the clouds

    (3/15/2024)

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

    Photo: Willie Webster

  • Cornices

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    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.

    Cornice 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 peak of warming. 

    (4/4/2023)

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

    Photo: Willie Webster

Avalanche Discussion

On Wednesday, temperatures will be cooler, and there will be more clouds than on previous days. However, it will be the sixth day in a row with a minimal overnight freeze. Prolonged warm temperatures have ushered in dangerous conditions and high uncertainty to the avalanche forecast.

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 during the month of 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, 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 which ran on a layer of facets buried in mid-February, just above the Jan 31st crust. 

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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