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Avalanche Forecast

Dec 20th, 2018–Dec 21st, 2018
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
3: Considerable
The avalanche danger rating at treeline will be considerable
Below Treeline
2: Moderate
The avalanche danger rating below treeline will be moderate
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
3: Considerable
The avalanche danger rating at treeline will be considerable
Below Treeline
2: Moderate
The avalanche danger rating below treeline will be moderate
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
2: Moderate
The avalanche danger rating at treeline will be moderate
Below Treeline
2: Moderate
The avalanche danger rating below treeline will be moderate

Regions: South Columbia.

Although the likelihood of avalanches is gradually decreasing, the potential to trigger large persistent slabs avalanches warrants conservative terrain choices.

Confidence

High -

Weather Forecast

THURSDAY NIGHT: Lingering flurries with 2-5 cm of snow, strong wind from the southwest, freezing level rapidly dropping, alpine temperatures drop to -10 C.FRIDAY: Cloudy with isolated flurries in the morning then clearing in the afternoon, moderate wind from the west, alpine temperatures around -10 C.SATURDAY: Clear in the morning then increasing cloud throughout the day, light wind from the south, alpine high temperatures around -8 C.SUNDAY: 5-12 cm of snow, light wind from the southwest, alpine high temperatures around -6 C.

Avalanche Summary

The storm snow is still reactive, especially in wind-loaded areas. Storm slabs have resulted in skier and explosive triggered avalanches (size 1-2), and natural avalanches (size 2-3.5) on a daily basis for the past week. Many of these avalanches were triggered from a distance (remote triggered). A recent remotely triggered size 2.5 avalanche occurred on Wednesday in the Valhalla Range on a north aspect around 2200 m. Most of the persistent slab activity on Wednesday was reported on north aspects between 2000-2300 m.

Snowpack Summary

Approximately 70-120 cm of recent storm snow sits on a weak layer of facets (sugary snow), surface hoar (feathery crystals) and a sun crust (on south aspects). Strong winds have promoted widespread slab formation, particularly with the most recent new snow available for transport.Another weak layer of surface hoar and sun crust that formed in mid November is up to 120 cm below the surface. This layer is most likely to be a problem in areas where the surface hoar sits on the sun crust. This combination is most likely found on steep, south facing slopes at treeline. The potential may exist for smaller avalanches to step down and trigger this deeper layer, resulting in large avalanches.At the base of the snowpack is a crust that formed near the end of October. Concern for this layer is dwindling but it may still be worth considering in places such as steep, rocky, alpine terrain, especially where the snowpack is shallow.

Avalanche Problems

Persistent Slabs

A widespread weak layer buried 50-100 cm deep has the potential to produced large avalanches and will likely take more time to heal.
Remote triggering is a concern, watch out for adjacent slopes.Use conservative route selection, choose moderate angled and supported terrain with low consequence.Use caution on open slopes and convex rolls

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Possible - Likely

Expected Size: 2 - 3

Storm Slabs

Snow from Thursday's storm will still be reactive, especially on steep and wind loaded terrain features at upper elevations.
If triggered the storm slabs may step down to deeper layers resulting in large avalanches.The new snow will require several days to settle and stabilize.Be careful with wind loaded pockets, especially near ridge crests and roll-overs.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Possible - Likely

Expected Size: 1 - 2