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Avalanche Forecast

Archived

Dec 28th, 2022–Dec 29th, 2022

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

Regions

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

Conditions are slowly improving as freezing levels drop but be mindful that deep instabilities are still present at higher elevations. If triggered storm slabs may step down to deeper layers resulting in large, destructive avalanches.

Confidence

Moderate

Avalanche Summary

On Tuesday, Explosives control produced numerous storm slab avalanches to size 2.5. They also had several persistent slab avalanche results, up to size 3. This is evidence that 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 were observed on all aspects at all elevations. Avalanches were up to size 3 and likely occurred during the rain event Sunday night.

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

Snowpack Summary

20-40 cm of dry storm snow sits above a rain crust found at alpine and treeline. 30-40 cm of wet snow is found beneath the crust. Extreme southerly winds have pressed surfaces and redistributed snow into thick slabs in alpine lees. 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. On Tuesday explosives control triggered numerous avalanches on these layers

Below treeline, a saturated snowpack is refreezing into firm surfaces. Total snow depths are roughly 90-140 cm at treeline and up to 200 cm in the alpine.

Weather Summary

Wednesday Night

Isolated flurries, trace accumulation. Southwesterly winds 20-30 km/h. Ridgetop low temperature -8 C. Freezing levels 500-700 m.

Thursday

Periods of snow, 5-15 mm. Southerly winds 20 km/h gusting to 40 km/h. Ridgetop high temperature -4 C. Freezing levels rise from 500m to 900 m by the end of the day.

Thursday night, light flurries continue bringing an additional 5 mm and 900 m freezing levels.

Friday

Cloudy with flurries, 10-15 mm. Southerly winds 40 km/h. Ridgetop high temperature -5 C. Freezing levels hover from 800 m to 1100 m.

Saturday

Cloudy with isolated flurries, 2-5 mm. Light to moderate southwesterly winds. Ridgetop high temperature -5 C. Freezing levels hover near 1000 m.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • In times of uncertainty conservative terrain choices are our best defense.
  • Continue to make conservative terrain choices while the storm snow settles and stabilizes.
  • 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.