Bulletin d’avalanche

West Slopes Central

Northwest Avalanche Center
Voir sur la carte

Danger d’avalanche

Sat
Alpin
2 · Modéré
Limite forestière
2 · Modéré
Sous la limite
2 · Modéré
Open full map
Périmé — ce bulletin a expiré 6 years ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

Steer around high elevation slopes 35 degrees and steeper with evidence of fresh wind loading. Concern for surprising wet avalanches still lingers in isolated areas, and steep slopes with large crevasse-like cracks or wet unconsolidated snow should be avoided. Non-avalanche issues like variable snow surfaces, open creeks, and downed trees may be your biggest hazard at lower elevations. 

Problèmes avalancheux

  • Wind Slabs

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

    Expect a few inches of new snow above 5000ft Thursday night and Friday. Winds may drift the new snow into shallow slabs that could be reactive to human traffic in leeward upper elevation terrain greater than 35 degrees. Uncertainty still exists regarding the sensitivity of thicker, older slabs of wind drifted snow formed earlier in the week. They may be gaining strength and harder to trigger, but the potential for large and destructive avalanches still lingers in isolated alpine areas. Be ready to make assessments if you travel to higher elevations and ease into terrain slowly. Watch for clues of instability like shooting cracks and collapses, and feel for sudden changes in snow surface texture and hardness. Avoid slopes with similar characteristics to those where you see recent avalanches, and seek out sheltered and lower angled terrain to reduce your risk. 

    (1/6/2021) Human caused cornice failure near Huntoon Point that fell and triggered a large avalanche (D2) on a north aspect at 5000ft.

  • Glide Cracks

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Unlikely
    Taille
    2–3

    Numerous glide avalanches occurred Monday-Wednesday with several inches of rain to 6000ft. The snowpack was heavily saturated and continues to drain free water lubricating the ground. Warming temperatures Thursday, and a round of light rain to 5000ft over the next 24hrs will continue to delay a solid freeze. Under these conditions, the entire snowpack could still release in steep areas with smooth ground cover or rock slab. Glide avalanches are difficult to predict, but cracks, which usually form first, are a good indicator. Watch for deep cracks in the snow in steep areas, usually with ground visible at the bottom. Stay off slopes where you see these cracks or any slopes with similar characteristics. With additional light rain and fluctuating snow levels, watch for loose wet avalanches in steep rocky terrain. Stay off steep slopes if you find wet, punchy, unconsolidated snow. Wet avalanche concerns will be limited where you encounter a firm and frozen surface crust.

    (01/13/21) A very large glide avalanche and other glide cracks in northerly terrain near 4500-5000ft on Shuksan Arm. Photo: Ben Williamson

Avalanche Discussion

A hazardous atmospheric river event (observed category 3-5 AR along the WA and OR coast) delivered 5-10in of water to the west slope of the Cascades January 10-13. Not surprisingly, a widespread natural avalanche cycle occurred as a result. Numerous dry snow avalanches within new and wind drifted snow occurred at upper elevations where precipitation fell as snow. Many were large breaking 1-2ft deep, while others grew very large breaking several hundred feet wide and running thousands of vertical feet like on Sloan and Whitehorse pictured below. Wet avalanches occurred in many areas as heavy rain fell up to 6000ft, including large loose wet and glide avalanches. Evidence of the recent avalanche cycle is impressive and easy to find. But, the snowpack is adjusting and primary avalanche concerns now shift to surface instabilities driven by incoming weather.

During the ongoing Covid-19 pandemic, continue to follow the latest guidance from local, state, and federal health officials. Avoid unnecessary risks that could impact first responders and stress medical resources.  Wear a mask when appropriate, practice social distancing, and consider recreating closer to home.

Régions couvertes