Avalanche forecast

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Northwest Avalanche Center
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Avalanche danger

Wed
Alpine
3 · Considerable
Treeline
2 · Moderate
Below
1 · Low
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Highlights

Dangerous conditions persist at upper elevations, where stiffer slabs over 2ft deep may be easily triggered. Outside of wind exposed areas, riding conditions are excellent but the soft new snow may still slide easily on a recently buried layer of surface hoar and crust. Consider sticking to lower-angled and well-supported slopes away from larger terrain features.

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1.5–2.5

    Strong winds created stiffer slabs over the weekend. As temperatures cooled off, the winds ramped down and these slabs may be hidden by softer new snow. These slabs rest on a layer of faceted grains, surface hoar and crusts. The strongest crust at the base was buried in late January. If an avalanche breaks on this layer it could be 1.5-2ft+ deep, and potentially fracture across terrain features. 

    Because of the nature of these weak layers, avalanches could be triggered from adjacent slopes. The most likely place to trigger one of these would be beneath heavily loaded ridgelines and below large cliff outcroppings. Whumphing collapses are signs of instability to heed. Targeted snow profiles can identify the weak structure, look for it on shaded aspects above 6,000ft. To avoid the problem, you can stick to lower angled and sheltered slopes, away from larger terrain features. 

    (2/26/2024) There are a few sets of tracks that are barely visible. One of which comes right into the crown line. Photo: John Barkhausen

  • Storm Slabs

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

    Soft slabs up to a foot thick could break within the new snow, or at the old snow interface. The new snow recently buried a layer of facets and surface hoar on sheltered slopes, even on southerly aspects. If you find a pocket of buried surface hoar,  slides may fracture widely. Loose snow slides may also run fast and far on Tuesday, and are more likely on very steep slopes outside of wind exposed areas. Look for fan shaped avalanches to clue you into these. Any avalanche at mid and upper elevations has the potential to break a foot or so deeper, on a crust from late January. If this were to happen, it could become a larger and more destructive slide.

    You can look for signs of instability like shooting cracks, and listen for whumphing collapses. Stick to lower angled slopes and simple terrain, away from larger terrain features like alpine cirques and starting zones.

Avalanche Discussion

Observers reported a couple of ski triggered avalanches up to size D1.5 on Monday. These were from steeper unsupported E facing slopes. A few naturals including an impressively wide natural was also observed beneath cliffs in Blue Lake cirque. The observers in this drainage found lots of whumphing collapses on a layer of faceted snow 2ft down above a crust from late January. Further east on Delancey, an observer found less new snow and no notable instabilities. You're likely to find at least 6-14" of new snow at mid elevations, with deeper areas of drifted snow.  Tuesday night and through the day Wednesday, another impactful winter storm arrives. Expect very dangerous avalanche conditions on Wednesday with the potential for many natural large avalanches. 

Before the recent stormy pattern started on Sunday, observers had been finding weak surfaces including surface hoar and facets, sometimes overlying a thin sun crust. The wind may've helped knock down some and break up some of these grains, but we should assume much of it was buried intact on the 24th. 

On shady slopes, at mid and upper elevations, there is up to 2.5ft of recent snow over a stronger crust from January 31st. Observers have found a thin layer of weak facets just above the 1/31 (elsewhere early February) crust. Lower elevations hold substantially less new snow over this crust and often don't harbor the associated facets. 

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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