Bulletin d’avalanche

West Slopes Central

Northwest Avalanche Center
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Danger d’avalanche

Sun
Alpin
4 · Fort
Limite forestière
4 · Fort
Sous la limite
4 · Fort
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Périmé — ce bulletin a expiré 2 years ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

Avoid travel on and below all avalanche terrain, even the runouts of big slopes in terrain way above you. Very dangerous conditions are expected to develop throughout the day as heavy wet snow and rainfall overload a dry snowpack. High danger and large natural avalanches are expected to continue overnight into Sunday morning. 

Problèmes avalancheux

  • Wet Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Very Likely
    Taille
    2–3.5

    It might take some time on Saturday for High danger and large natural avalanches to develop. It’s still a safe bet that continued rain and snowfall will destabilize the snowpack throughout the North Cascades by the end of the day. The rain-snow line will push up into high elevations in the afternoon. This will increase the likelihood of seeing very large avalanches run long distances, maybe even to valley bottom.

    Dry snow slab avalanches might be a thing at the highest elevations, but wet snow will rule most areas. Expect to see some combination of wet slab, glide, loose wet, and cornice fall avalanches by the end of the weekend. Wet, soggy snow will undermine most attempts at enjoyable recreation in low-angle terrain.

    It’s easy to avoid big steep slopes that you can see. Saturday could be the kind of day that avalanches can run down from slopes above that you can’t see. Know what is above you if you are headed into the mountains.

    Debris from a very large wet avalanche blocking the Church Mt. Road above Hwy 542. March of 2023.  A vehicle was actually stuck on the other side of this pile for some weeks before it melted out enough to drive over.

Avalanche Discussion

Minimal precipitation was recorded at West Central weather stations on Friday, with up to 0.2" falling in the form of rain at low elevations and very wet snow at mid-elevations. Temperatures hovered in the low to mid-30s and winds steadily increased through the day. To the north, wet snow was found up to at least 5300', and numerous wet avalanches were reported. Some were D2 in size and larger than expected. Conditions were similar at the passes, with light precipitation, mild temperatures, and an increase in wind speeds in the afternoon

Whatever the snowpack structure is going into the weekend, it will be very different by the time Monday rolls around. There are a few interfaces that could be the most reactive when weakened by liquid water. The most recent interface buried on the 19th produced a number of natural and human-triggered avalanches on Wednesday but was observed as stronger the day after. It's possible that weak snow buried on the 15th (actually on the 13th at Snoqualmie Pass) is still quite weak in some areas and was responsible for additional avalanches - but this hasn't yet been confirmed as of late Friday afternoon. Finally, the crust and facet layering at the January Drought Layer is found anywhere from 2'-5' deep and could wake up when provoked by heavy loads.

It's rarely a sure thing that very large natural avalanches will occur. This weekend is one of the times when the snowpack setup and weather conditions to have them are in place. 

Régions couvertes