Bollettino valanghe

Stevens Pass

Northwest Avalanche Center
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Pericolo valanghe

Fri
Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
1 · Debole
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Non aggiornato — questo bollettino è scaduto 4 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

With warmer temperatures in store, Thursday will be a good day to stay out of large, rocky terrain features. You're most likely to trigger smaller avalanches in recent snow in wind-exposed terrain. While less likely, you could start a dangerous and very large and persistent slab avalanche on a deeply buried crust layer.

Problemi valanghivi

  • Wind Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1–1.5

    Consider that you will need to avoid triggering wind slabs by avoiding typical leeward and wind-loaded slopes, and also avoid areas where you could trigger much more dangerous avalanches (see below). Steer clear of large avalanche paths and especially terrain that is very steep, convex, with unsupported and rocky features. Look for signs of wind slabs like deeper drifts near ridgetops, slightly stiffer snow, shooting cracks. Check to see how the new snow is bonding to the recently buried crust with quick tests like hand shears, kick turn tests, and small test slopes.

     

    (2/14/2023)

    Mt McCausland summit with recently formed wind drifts and signs of loading.

    Photo: Public obs

  • Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    2–3

    The best way to stay safe is to stay well away from big start zones that are steep, rocky, unsupported, and with weak trigger points. Default to well-supported terrain features and smaller pieces of terrain. Be sure that you're stopping in truly safe terrain, well out from under the reaches of overhead avalanche paths. The last reported persistent slab avalanche occurred on Monday, the 13th. The recent snow and warming may contribute to the lingering chance of triggering very large and dangerous avalanches. You probably won't get signs of instability with these avalanches. If you manage to trigger one, it would be surprising and destructive. A thin weak layer resting on a slick crust from mid-January can be found about 3 feet below the snow surface. The layer was responsible for natural and triggered avalanches from Feb 8-13th.

    (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: Public Obs

Avalanche Discussion

On Wednesday, observers in Lanham creek reported test results in two profiles (E/NE, 5,600ft) that broke suddenly but didn't propagate on a crust that was buried on Sunday. More notable were large column tests that still indicated the potential for an avalanche to propagate on the MLK crust, 3 feeet below the surface.  From Sunday night to Monday night, 6-12" snow accumulated with totals increasing at higher elevations and subtle wind transport. 

The last week brought a widespread cycle of avalanches running on steep, leeward slopes, just below ridges that saw wind loading including Windy Ridge and the Rooster Comb, above Lake Susan Jane. Some of these are suspected to have run on a crust/weak layer about 2.5 feet below the surface. The natural cycle mostly occurred on Feb 8th. A very large avalanche with an 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 nearby 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.

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