Avalanche Forecast

Archived

Feb 22nd, 2023–Feb 23rd, 2023

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 unlikely, human triggered possible.

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. Winds switching direction have redistributed the new snow onto a variety of aspects.

Confidence

Moderate

Avalanche Summary

Reports on Tuesday and Wednesday reflect a natural avalanche cycle in the Coquihalla area Monday night and Tuesday. Avalanches were reported as size 2-3 wind slabs, storm slabs and persistent slabs on northwest, northeast and southeast aspects in the alpine and treeline elevation bands. The persistent slab avalanches were suspected to have run on the facet/crust layer buried in mid-January (outlined in the avalanche problem section).

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 has been redistributed by primarily southwest winds switching to northerly.

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 appears to have 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

Wednesday Night

Cloudy with clear breaks. Light to moderate north east. Treeline temperature -18 °C.

Thursday

Mix of sun and cloud. Moderate north east wind. Treeline temperature -17 °C.

Friday

Mix of sun and cloud. Light northeast wind. Treeline temperature -12 °C.

Saturday

Mainly cloudy with sunny breaks. Moderate southwest wind. Treeline temperature -7 °C.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

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.
If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
Pay attention to cornices and give them a wide berth when traveling on or below ridges.

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.