Bulletin d’avalanche

Olympics

Northwest Avalanche Center
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Danger d’avalanche

Sat
Alpin
3 · Marqué
Limite forestière
2 · Modéré
Sous la limite
2 · Modéré
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Périmé — ce bulletin a expiré 8 months ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

The avalanche hazards will become more aspect dependent by Friday. At upper elevations or if you experience active snow transport, wind loading lee slopes will be reactive on slopes steeper than 35 degrees. If the sun makes an appearance and winds remain calmer, keep out from under steep slopes where deep dry snow will rapidly destabilize as it warms.

Problèmes avalancheux

  • Wind Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    1–2

    Although recently formed wind slabs were stubborn at middle elevations, they may retain more reactivity at upper elevations. Fresh slabs will also form if SW winds increase during the day on Friday. ONP Rangers reported 1-1.5 ft of dry snow available for transport on S aspects, just a few hundred feet below ridgelines, so if this starts moving, expect to find increasing slab reactivity on the lee side. While most of the deep snow is right-side-up, you can use small test slopes and wind pillows to gauge the reactivity in your terrain. If you find cracking or sudden settlement of wind pillows, then steer around wind loaded slopes 35 degrees and steeper.

    Example: This small wind drifted pillow cracked. Features like this provide clues to how nearby larger slopes could react. 

    Photo: Dallas Glass

  • Loose Wet

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    1–1.5

    A sharp shift to warmer conditions and filtered sunshine on Friday may destabilize deep, cold low-density snow. The January sunshine can really only do damage on steep slopes receiving direct sunshine. So, pay attention to the clock and the slopes above you. Snow will start shedding off rocks and cliffs as these features warm first. It may then start entraining moist or dry surface snow to form avalanches large enough to bury you, particularly around creek beds and other terrain traps. Rollerballs are yet another sign you should adjust your aspect and reduce your overhead hazard. In heavily wind-affected terrain, if the winds ramp up, or if clouds are thicker, this problem may not materialize.

    Example: Steep slopes shedding and entraining previously dry snow. 

    Photo: ONP Rangers

Avalanche Discussion

ONP Rangers traveled up to Maggie's Ridgeline on Thursday. They found 27-30 inches of snow above the 1/3 crust. This crust was still moist and blended into the recent snow below 5000 ft, but hardens and becomes more prominent above this elevation. On some SW-S-SE aspects, you may also encounter a 1/6 sun crust. The right-side-up storm snow is believed to be well bonded to either crust if you find them in your terrain. Winds had scoured slopes near ridgelines. Periods of W winds loaded E aspects Tuesday and Thursday, but you might find reverse loading from a period of SSE winds on Wednesday.

Storm slab and wind slab reactivity were surprisingly limited on Thursday. Thus, it will take a shift in temperature or winds to increase the avalanche activity on Friday. With rising temperatures, increased sunshine, and increasing SW winds, we're not sure exactly how things will play out. Plan to adapt. If temperatures are warm and sunny, adjust to cooler shaded aspects. If conditions are windy, stick to lower angle slopes if you move onto the lee side of ridgelines, focusing on active transport to guide you away from the most reactive slopes.

Snowfall conditions have markedly improved throughout the region. There is now 10" of snow on the Hurricane Ridge Road down to 3400 ft.  That said, snow depths remain below normal, and early-season hazards are widespread (open creeks, downed trees, rocks, etc.), especially on windward slopes and at lower elevations.  Use caution when navigating the early-season snowpack. 

Régions couvertes