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Avalanche Forecast

Archived

Feb 23rd, 2024–Feb 24th, 2024

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

Regions

Coquihalla, Harrison-Fraser, Manning, Skagit.

Monitor new snow depths and reactivity as the storm gets started. Wind loaded features and places large surface hoar is being buried will likely be the first to reveal instability.

Confidence

Moderate

Avalanche Summary

No new avalanches have been reported in the region in quite some time. The situation should begin to shift on Saturday as up to 15 cm of new snow and elevated southwest winds invade. Small new wind slabs will be the initial concern on Saturday. By Sunday we should see touchy storm slabs forming over an array of problematic surfaces.

Snowpack Summary

Up to about 15 cm of new snow should accumulate in the region through Saturday. It will add to a skiff of windblown snow that recently began to bury a variety of surfaces including large surface hoar in sheltered terrain, a crust on south aspects and on all aspects below treeline, and old wind-affected surfaces in exposed terrain.

A widespread crust exists 25-40 cm below the surface with up to 5 cm of weak, faceted snow immediately above it. Surface hoar was previously found above the crust in some parts of the region. Old, likely stubborn wind slabs formed over this problematic layering are a lingering concern. Operators in the Hope area observed several whumpfs on this layer on shaded treeline aspects Thursday.

Weather Summary

Friday night

Becoming cloudy then flurries bringing around 5 cm of new snow or just over. 40 to 50 km/h southwest alpine wind, increasing. Freezing level falling to 1100 m.

Saturday

Cloudy with continuing flurries bringing 5-10 cm of new snow. 40-50 km/h southwest alpine wind. Treeline temperature -3 C with freezing level to 1300 m.

Sunday

Cloudy with moderate to heavy snowfall bringing 20-30 cm of new snow, including overnight amounts. 60 - 80 km/h southwest alpine winds, increasing. Treeline temperature -3 °C with freezing level to 1300 m.

Monday

Cloudy with diminishing flurries bringing 15-25 cm of new snow, including overnight amounts. 20 - 30 km/h west or southwest alpine winds, easing. Treeline temperature -5 with freezing level falling to 600 m.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Wind slabs are most reactive during their formation.
  • Carefully evaluate steep lines for wind slabs.
  • Carefully assess open slopes and convex rolls where buried surface hoar may be preserved.

Problems

Wind Slabs

Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind 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.