Avalanche forecast

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Northwest Avalanche Center
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Avalanche danger

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

The warmest temperatures of the week will keep wet avalanches a concern through Sunday. You could still trigger large and dangerous avalanches on old weak layers of snow. Put lots of space between where you travel and large avalanche paths, especially where you see cornices looming overhead.

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1.5–2

    You may still be able to trigger dangerous persistent slab avalanches on slopes 35 degrees and steeper. Wet avalanches and cornice fall could also be the trigger. Avoid being on or under suspect slopes, especially on NW-E near and above treeline. Put a large buffer of terrain between where you travel and large start zones. Minimize your exposure to large avalanche paths and look for safe locations to stop or regroup.

    Reported avalanches have largely come from slopes on the north half of the compass near and above treeline. "Red flag" signs of the danger include whumphing collapses, shooting cracks, and tests that propagate or fail suddenly.  You can dig down and find the culprit, the late-January weak layer, 1-2 feet below the surface.  In many areas, this layer is a combination of weak sugar-like facets sandwiched between two buried crusts.  Deeper and more consequential slabs may be found on lee slopes near the Cascade crest and near and above treeline where westerly winds have previously created thick slabs. In the eastern part of the zone, a similar weak upper snowpack structure exists but the slabs resting above the persistent weak layer may be thinner.  See or hear something?  Let us know.  

    (2/5/2022)

    A skier triggered avalanche near Maple Pass. Three people were caught, one was carried up to 600ft with no injuries. E, 6,600ft

    Photo: NWAC public obs

  • Loose Wet

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–2

    Wet avalanches will be unlikely first thing in the morning when snow surfaces will be frozen. You'll be able to trigger wet avalanches more easily on steep sunny slopes as the day warms and the sun melts the snow. Avalanches could be big enough to bury you near and above treeline. Make quick observations throughout the day to feel how wet and weak the snow is.  You can use a pole, shovel, your boots, or your hands.  If you sink into the snow up to the top of your boots in wet snow, it's time to move to lower-angled or more frozen slopes.  Even small wet avalanches could be dangerous in very steep terrain or around rocks and cliffs.  

    Don't linger near or under cornices, as they could fall with melting from the sun. While large blocks of hard snow crashing down a slope are a hazard in their own right,  they may also trigger large avalanches on the slopes below. Give them a wide berth on ridgelines during this warm spell. 

     

    (2/10/2022)

    Example wet loose avalanches.

    Photo: Matt Primomo

Avalanche Discussion

On Saturday, professionals reported a recent natural D1.5 avalanche on an east aspect, near treeline on Porcupine Peak. It occurred in shallow rocky terrain and is suspected to have run on the late January weak layer. An NWAC forecaster also reported a recent natural persistent slab avalanche in the West North zone. On Thursday, observers noted a cornice fall that triggered a large wind slab avalanche in rocky north facing terrain. Professionals have been finding facets sandwiched between crusts as the culprit for persistent slab instabilites. Widespread whumpfing, rolling collapses, and remote triggering of avalanches have been fairly common over the last week, though signs of instability have become less frequent in some areas. There's considerable uncertainty about how the very mild temperatures and strong sun will affect these persistent slabs, but now is not a good time to step out into bigger terrain.

While there are some signs that the snowpack is gaining strength, tests continue to show sudden results on northerly aspects on the late January crust/persistent weak layer throughout the Highway 20 corridor including at Harts Pass,  Silverstar area, Hairpin Valley and on Kangaroo Ridge,  A party of four triggered a large persistent slab near Maple Pass and three were partially buried last weekend. Thankfully, all finished the day uninjured. A fatality occurred on the Duffey Lake Highway in Canada on a similar persistent weak layer the same day, and a Special Public Avalanche Bulletin is in effect through the weekend.

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