Avalanche forecast

Stevens Pass

Northwest Avalanche Center
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Avalanche danger

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

A complicated snowpack leads to multiple avalanche problems, so Tuesday is a good one to choose simple and less steep slopes. A great deal of uncertainty exists with some potential to trigger very large and wide avalanches on a deeply buried crust layer. You could find reactive wind slabs as you gain elevation, and watch for loose wet avalanches to become active during the middle of the day. 

Avalanche problems

  • Wind Slabs

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

    With the storm just winding down, seek out lower angled and less exposed slopes to get a feel for how the new snow reacts. There could be interstorm layers that don't bond well, and winds have likely created more cohesive slabs on higher, exposed slopes. You're likely to find clues to wind slab like deeper drifts near ridgetops, and slightly stiffer snow. Look for signs of instability like shooting cracks and fresh slab avalanches. Check to see how the new snow is bonding to the recently buried crust with practical tests like hand shears, kick turn tests, and small test slopes.

    It'll be wise to give the snow a day or two to settle out before entering upper elevation starting zones. The highly uncertain element is the continued potential for very large slabs to fail on old weak snow/crust layers. Steer clear of large, upper elevation slopes, especially if they are convex or unsupported and recently loaded to avoid this risk. 

    (2/7/2023)

    Example storm slab

    Photo: Dallas Glass

  • Persistent Slabs

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

    The new snow may increase chances for natural and human triggering of large to very large slab avalanches a two to four feet deep. You're not likely to get signs of instability with this situation, but if you triggereed one it would be surprising and destructive. These have occurred most recently from large, open and somewhat unsupported slopes on both Northeast and Southerly aspects. Persistent weak layers in the form of weak snow from early February and slick crusts from January have been active for the past week, and continued activity appears quite possible.

    With this problem lurking, default to well supported terrain features. To avoid the risk, shy away from large, steep, open and unsupported starting zones.

    (2/12/2023)

    Very wide crown spanning most of the south face of Jove Peak. This slide very likely occurred during the middle of the day on Sunday.

    Photo: Julia

  • Loose Wet

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–1.5

    Small wet loose slides, or solar induced 'moist' loose slides may occur as the sun rises higher into the sky on Tuesday. Loose dry slides may also entrain on steep, shaded slopes. Look for signs of instability as the daytime progresses on steep slopes that face the sun. The recent very large avalanche was on a south facing slope, and small rollerballs were observed to have occurred before it released naturally. It's not too often that we're concerned with small loose slides intiating monsters like this, but on Tuesday it'll be a good consideration.

    In any case, don't let yourself get caught in small loose slides, and steer clear of large steep slopes that pick up direct sun. 

    (1/1/2023)

    Wet loose avalanches in alpine terrain on the south face of Sefrit.

    Photo: Jason Speer

Avalanche Discussion

An observer found 6" of new snow with some wind drifting on Monday at 1:30pm in the Skyline area. The convergence zone shifted back north and should add another handful of inches of new snow overnight. Winds are apparently drifting a fair amount of snow at ridgetops as I write. 

A very large avalanche with impressively wide crown was observed off the S face of Jove Peak on Sunday. It appears this slide ran naturally in the middle of the day with the warming temperatures and sun likely to have played a role in its release. On Saturday, a report came in of a large skier triggered slab on a northeast aspect at around 5,400ft just north of Lake Josephine. The second skier on the slope triggered the slide in a steep, unsupported feature, and the crown broke above him. Another skier triggered slide occurred on the 9th from a nearby slope to the above mentioned involvement. These incidents speak to continued instabilities and lack of bonding of recent storm snow to older weak snow and crusts. Compiling all the information on profiles that I've seen, it appears this problem is hit or miss. Some slopes hold weak enough snow over a crust where it could propagate into an avalanche, and others don't. It's basically a gamble as to which ones do and don't though.

February 8th was very active, and control work at the ski area that day produced widespread storm slab results, 3 were reported to have run down to a recent crust. Observers also reported large, natural slab avalanches on steep, leeward slopes, just below ridges that saw wind loading including Windy Ridge and the Rooster Comb, above Lake Susan Jane. A couple of these also were suspected to have run on recent crust interfaces as well. 

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