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Avalanche Forecast

Archived

Mar 12th, 2024–Mar 13th, 2024

Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural and human triggered avalanches likely.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches possible, human triggered probable.
Alpine
Natural and human triggered avalanches likely.
Treeline
Natural and human triggered avalanches likely.
Below Treeline
Natural and human triggered avalanches likely.

Regions

Coquihalla, Manning, Skagit.

Recent snow and wind have created dangerous avalanche conditions. Stick to smaller, low-angle slopes.

Confidence

Moderate

Avalanche Summary

Reports of avalanche activity have been limited. A notable size 2 persistent slab avalanche was observed in Manning Park (photo below). It likely occurred naturally over the weekend. A few small (size 1) storm and wind slab avalanches were observed over the weekend.

Snowpack Summary

Tuesday's storm brought 15 to 30 cm of snow, likely forming fresh slabs at upper elevations and wind-loaded terrain. This snow sits above a thin crust on south aspects and settling powder on north aspects.

There has been evidence of two persistent weak layers roughly 80 to 120 cm deep. The upper one is a thin layer of facets and crusts or surface hoar while the deeper one is facets above a thick crust. While we have not seen many reports of persistent slab avalanches in this region, these layers should not be trusted based on notable activity in neighbouring regions.

Weather Summary

Tuesday Night

Cloudy. 30 km/h west ridgetop wind. Treeline temperature -6 °C.

Wednesday

Cloudy. 20 km/h northwest ridgetop wind. Treeline temperature -4 °C with freezing level rising to 1200 m.

Thursday

Mostly sunny. 35 km/h northwest ridgetop wind. Treeline temperature +2°C with freezing level climbing to 3000 m.

Friday

Mostly sunny. 10 km/h northeast ridgetop wind. Treeline temperature +8 °C with freezing level climbing to 3300 m.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Storm snow and wind is forming touchy slabs. Use caution in lee areas in the alpine and treeline.
  • Carefully monitor the bond between the new snow and old surface.
  • In times of uncertainty conservative terrain choices are our best defense.

Problems

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.

Persistent Slabs

Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.