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

Dec 27th, 2022–Dec 28th, 2022

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

Regions

Sea To Sky, Brandywine, Garibaldi, Homathko, Powell River, Spearhead, Tantalus, Tetrahedron.

On Tuesday explosives control produced numerous large destructive avalanches on the persistent weak layer.

Human-triggered storm slab avalanches may step down to deeper layers resulting in high-consequence, large, destructive avalanches.

Confidence

Moderate

Avalanche Summary

On Tuesday, Explosives control produced several persistent slab avalanches, up to size 3. This is evidence that with the persistent weak layer is still with us and will result in large destructive avalanches with the right trigger.

On Monday, evidence of a natural avalanche cycle, both wet slab, and wet loose avalanches, was observed on all aspects at all elevations. Avalanches were up to size 3 and likely occurred during the rain event Sunday night.

On Sunday, explosives control triggered several storm slab avalanches up to size 2.5. Storm slabs were 30-50 cm deep. Explosive also triggered one size 2.5 persistent slab avalanche that is suspected to have run on the Dec 8 surface hoar.

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

Snowpack Summary

40 - 50 cm of storm snow has fallen since Dec 22. Extreme southerly winds have pressed surfaces and redistributed snow into thick slabs in alpine lees. A melt-freeze crust is found below 1800 m. The new snow covered a layer of weak and unconsolidated snow produced by the recent cold weather.

A number of layers persist deeper in the snowpack, consisting of facets, surface hoar, and crusts. Most recently, these layers have been unreactive and this heavy load of new snow should provide insight into any deeper instabilities. Total snow depths are roughly 90-140 cm at treeline and up to 200 cm in the alpine.

Weather Summary

Tuesday Night

Precipitation continues tonight with another 10-20 mm. Variable 25 km/h winds. Ridgetop low temperature -7. Freezing levels 800 m.

Wednesday

An additional 2 - 5mm of precipitation diminishes in the morning. Southwesterly 40 km/h winds easing to 20 km/h in the afternoon. Ridgetop high temperature -7. Freezing levels 800 m.

Thursday

Scattered flurries, 10-20 mm. Southerly 40 km/h winds increasing in the afternoon. Ridgetop high temperature -4. Freezing levels hover from 500 -1000m.

Friday

Cloudy with flurries, 15 - 25 mm. Westerley 20 km/h winds. Ridgetop high temperature -4. Freezing levels hover near 800 - 1300 m.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Storm slabs in motion may step down to deeper layers resulting in large avalanches.
  • Fresh snow rests on a problematic persistent slab, don't let good riding lure you into complacency.
  • Be alert to conditions that change with aspect and elevation.

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.