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Avalanche Forecast

Archived

Feb 26th, 2023–Feb 27th, 2023

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

Regions

Coquihalla, Harrison-Fraser, Manning, Skagit.

Don't let good visibility and the desire to ride deep powder lure you into consequential terrain. Natural activity may taper but human-triggered storm slabs remain LIKELY! Sheltered and shaded terrain will offer the best and safest riding.

Treat the avalanche danger as HIGH and avoid avalanche terrain and overhead exposure during periods of strong solar radiation.

Confidence

Moderate

Avalanche Summary

As northerly outflow winds picked up on Wednesday, several natural and human-triggered wind slabs (size 1) were reported throughout the region. These slabs occurred on a variety of aspects in the alpine all the way down to below treeline terrain.

At this time of publishing on Sunday, no new avalanches have been reported.

Looking forward to Monday, storm slabs are expected to remain reactive to human triggering, particularly in wind-loaded areas or on sun-exposure slopes. Be alert to changing conditions with elevation, aspect and exposure to the sun.

Please continue to post your reports and photos to the Mountain Information Network.

Snowpack Summary

Last weekend's storm brought 15-30 cm of new snow down to valley bottom. This new snow is expected to bond poorly to the stiff wind slabs and near-surface facetting formed by recent wind and cold temperatures.

A melt-freeze crust formed in mid-January is buried up to 90-140 cm deep. In some areas, small faceted crystals can be found above the crust. This layer has been reactive during the storm Tuesday night and Wednesday this week. The snow below this layer is well consolidated.

Snowpack depths are just below seasonal averages. Total amounts range from 150 to 300 cm at treeline, but decreases significantly below 1500 m.

Weather Summary

Sunday night

Clear periods with isolated flurries. Alpine temperatures drop to a low of -10 °C. Ridge wind 20 to 50 km/h from the southwest. Freezing level at valley bottom.

Monday

A mix of sun and cloud with isolated flurries. Alpine temperatures reach a high of -2 °C. Ridge wind o15 to 35 km/h from the southwest. Freezing level 600 metres.

Tuesday

A mix of sun and cloud with isolated flurries. Alpine temperatures reach a high of -4 °C. Ridge wind light from the southwest. Freezing level 500 metres.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Give the new snow several days to settle and stabilize before pushing into bigger terrain.
  • Seek out sheltered terrain where new snow hasn't been wind-affected.
  • Be alert to conditions that change with elevation and sun exposure.
  • Avoid slopes when the solar radiation is strong, especially if they have large cornices overhead.
  • Brief periods of sun could quickly initiate natural avalanche activity.

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.