Bollettino valanghe

East Slopes North

Northwest Avalanche Center
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Pericolo valanghe

Sun
Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
1 · Debole
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Non aggiornato — questo bollettino è scaduto 5 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

While unlikely, continue to weigh the consequences of triggering a large persistent slab avalanche while choosing terrain Saturday.  Also use caution in very steep terrain where you could trigger a fast-moving sluff.  An incoming storm Saturday night will lead us into a stormier pattern. 

Problemi valanghivi

  • Loose Dry

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

    You can still find loose dry snow on shady aspects and in wind-sheltered terrain at mid and upper elevations near the Cascade crest.  In these areas, use caution on convex roll-overs or slopes 40 degrees or steeper.  You're likely to find a thin crust on steeper slopes that have been exposed to the sun over the last few days. While small, loose avalanches can be dangerous if they push you into terrain traps such as trees, rocks, or gullies. 

    Example of small loose dry or sluff avalanche. They are only an issue in the wrong piece of terrain. 

  • Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Unlikely
    Dimensione
    2

    It has been about 2 weeks since the last reported persistent slab avalanche but snowpack tests and occasional pieces of feedback while traveling, like collapses or whumpfs, continue to give us pause before moving on from this problem.  Even though it's unlikely,  the consequences of triggering a persistent slab avalanche could be serious.  You can find and test the weak layer in snowpack tests on shaded slopes near and above treeline.  While the depth varies, you can find the late January facet/crust interface somewhere between 2-3" below the snow surface.  This layer is a combination of weak sugar-like facets sandwiched between two crusts in many areas. Sometimes you'll find weaker snow above the crust. The weak layers are deepest near and west of the Cascade crest and in wind deposited areas. 

    Red flags that you may trigger a persistent slabs include whumpfing, collapses and snowpack tests that pop or drop suddenly. When in doubt, consider steering clear of shallow, rocky, or unsupported steep slopes.

    (2/5/2022)

    Earlier this month a skier triggered an avalanche near Maple Pass. Three people were caught, one was carried over 400ft with no injuries. E, 6,600ft

    Photo: NWAC public obs

Avalanche Discussion

Saturday is a transition day while we wait for a much stormier pattern to begin, one that may awaken the persistent slab problem that's gone quiet over the last few weeks.  While we're still thinking about deeper layers,  Saturday is a great time to track the current snow surfaces ahead of the upcoming pattern change.  Earlier this week, small but fast moving loose dry avalanches were reported in very steep terrain.   A storm over President's weekend with strong westerly flow brought 10-14" of snow near the crest with little snowfall for areas further east.  This week has been very cold, with overnight lows regularly falling into the single digits or lower.  This has helped keep the recent snow loose on shadier aspects.  With some warming and abundant sunshine Friday,  professionals observed many wet loose sluffs releasing on steep sunny slopes.

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