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Avalanche Forecast

Archived

Feb 20th, 2023–Feb 21st, 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.

Updated on Tuesday at 6:10 AM. 15 to 20 cm of snow fell overnight creating dangerous avalanche conditions at treeline and alpine elevations.

Confidence

Moderate

Avalanche Summary

Most recent avalanche activity was reported as size 1-1.5 wind slabs in the alpine.

With heavy snowfall forecast for Monday night combined with strong winds, expect there to be an increase in natural avalanche activity in the alpine and treeline.

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.

A melt-freeze crust formed in mid-January is now buried up to 80-120 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

Monday Night

Cloudy with snow, accumulation 15-30cm. Wind strong southwest. Treeline temperature -5 °C. Freezing level 1300 m.

Tuesday

Mainly cloudy with flurries, accumulation 3-5cm. Wind light to moderate northwest. Treeline temperature -7 °C. Freezing level 400 m.

Wednesday

Mainly cloudy. Wind light to moderate northeast. Treeline temperature -14 °C.

Thursday

Mix of sun and cloud. Wind moderate north wind. Treeline temperature -16 °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.
  • 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.