Dashboard Regions Weather Stations Radar Alerts Glossary
Contact About
Log In

Register for an account and never miss a forecast again!

Register

Avalanche Forecast

Archived

Feb 28th, 2023–Mar 1st, 2023

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

Regions

Coquihalla, Harrison-Fraser, Manning, Skagit.

Overnight winds from the northeast may form fresh wind slabs on unexpected slopes. Wind slabs may remain sensitive to human triggering, particularly in wind-loaded areas.

Take a cautious approach and investigate the bond between the new snow and the old surface before committing to your line.

Confidence

Moderate

Avalanche Summary

On Monday, one size 1.5 natural storm slab was observed from a distance on a steep treeline convex roll, and a natural glide slab released size 2 from a south aspect at 1600 m and ran 300 m in length.

Looking forward to Wednesday, human-triggered storm slabs remain likely, especially in wind-loaded areas. Storm slab reactivity is expected to persist for longer than is typical due to the weak surface they are sitting on.

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

Snowpack Summary

Last weekend's 15-30 cm of new snow may have a poor bond to the underlying surface, consisting of stiff wind slabs and near-surface faceting 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

Tuesday Night

Clear periods. Alpine temperatures -8 °C. Ridge wind northeast 15 km/h. Freezing level valley bottom.

Wednesday

Cloudy with flurries up to 5 cm. of accumulation Alpine temperatures reach a high of -7 °C. Southwest wind 40 km/h and freezing level valley bottom.

Thursday

Snow amounts 15-25 cm. Ridgetop wind 40-70 km/h from the southwest. Alpine temperatures reach a high of -5 °C. Freezing level 600 m.

Friday

Cloudy with snow 5-10 cm. Alpine temperatures near -6°C. Ridge wind southwest 25 gusting to 50 km/h. Freezing level 500 m.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Recent wind has varied in direction so watch for wind slabs on all aspects.
  • Seek out sheltered terrain where new snow hasn't been wind-affected.
  • Carefully monitor the bond between the new snow and old surface.
  • Use extra caution around cornices: they are large, fragile, and can trigger slabs on slopes below.

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.