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Avalanche Forecast

Archived

Feb 21st, 2023–Feb 22nd, 2023

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

Regions

Coquihalla, Harrison-Fraser, Manning, Skagit.

25 to 40cm of new snow fell Monday night and Tuesday. Give the storm snow some time to settle and bond.

Confidence

Moderate

Avalanche Summary

At publishing time Tuesday afternoon there had been no reports of avalanche activity yet, however I would suspect there was a widespread natural storm slab avalanche cycle through the day.

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

Snowpack Summary

20-40 cm of new snow from the beginning of the week is being redistributed by primarily southwest winds switching to northerly.

A melt-freeze crust formed in mid-January is now buried up to 90-140 cm deep. In some areas, small facets are still found above the crust. This layer appears to be gaining strength but still remains a concern. 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

Tuesday Night

Mainly cloudy with clear periods. Light to moderate north and northeast wind. Treeline temperature -10 °C. Freezing level dropping to valley bottom.

Wednesday

Cloudy with sunny periods. Light to moderate northeast wind. Treeline temperature -12 °C.

Thursday

Mix of sun and cloud. Moderate northeast wind. Treeline temperature -13 °C.

Friday

Mix of sun and cloud. Light northerly wind. Treeline temperature -10 °C.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Continue to make conservative terrain choices while the storm snow settles and stabilizes.
  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Recent wind has varied in direction so watch for wind slabs on all aspects.
  • Storm slabs in motion may step down to deeper layers resulting in large avalanches.

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.