Avalanche Forecast

Archived

Mar 2nd, 2023–Mar 3rd, 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, 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.

Some areas of our region will experience heavy localized snowfall due to convection. Expect the hazard to increase with increased amounts.

Seek out sheltered terrain away from the wind to enjoy the best turns.

Confidence

Moderate

Avalanche Summary

On Tuesday, a few wet loose avalanches up to size 1 were reported below treeline.

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.

On Friday, natural and human-triggered storm slabs are likely. Storm slab reactivity is expected to persist for longer than is typical due to the weak surface they are sitting on.

Snowpack Summary

Up to 10 cm accumulation overnight will add to the 20 to 35 cm that fell yesterday. New snow should begin to settle on the 30 cm of settling snow that fell last weekend. The new snow may have a poor bond to the underlying stiff wind slabs and faceted snow formed by recent cold temperatures.

A melt-freeze crust formed in mid-January is buried up to 100 to 150 cm deep. In some areas, small faceted crystals can be found above the crust. This layer was reactive a week ago. 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 decrease significantly below 1500 m.

Weather Summary

Thursday Night

Cloudy, up to 10 cm accumulation, winds southwest 20 km/h gusting to 50, treeline temperatures -8 °C.

Friday

Cloudy with late-day sunny breaks in some areas, 8 cm accumulation with some west-facing slopes receiving up to 20 by the end of the day, winds southwest 20 km/h gusting to 50.

Saturday

A mix of sun and cloud, trace accumulation, winds southeast 30 to 30 km/h, treeline temperatures -5 °C, and freezing level climbing to 1200 m.

Sunday

A mix of sun and cloud, trace accumulation, winds southeast 15 km/h, treeline temperatures -5 °C.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

Avoid all avalanche terrain during periods of heavy snowfall.
Storm slab size and sensitivity to triggering will likely increase through the day.
Closely monitor how the new snow is bonding to the crust.
Use extra caution around cornices: they are large, fragile, and can trigger slabs on slopes below.

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.