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Archived

Avalanche Forecast

Dec 27th, 2018–Dec 28th, 2018
Alpine
2: Moderate
The avalanche danger rating in the alpine will be moderate
Treeline
2: Moderate
The avalanche danger rating at treeline will be moderate
Below Treeline
1: Low
The avalanche danger rating below treeline will be low
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

Regions: Lizard-Flathead.

Persistent slabs are tricky to manage. Avalanche activity is receding, but if triggered, an avalanche falling on the persistent weak layer could have serious consequences. Read the latest Forecaster Blog on the persistent slab problem here.

Confidence

Low - Due to the number of field observations

Weather Forecast

THURSDAY NIGHT: Mix of sun and cloud. Light west wind. Alpine low of -13C.FRIDAY: Mainly cloudy with isolated flurries, trace accumulation. Light to moderate west-southwest wind. Alpine high of -11C.SATURDAY: Flurries, 5-15 cm accumulation. Moderate southwest wind with strong gusts. Freezing level rising to 1500 m.SUNDAY: Mainly cloudy with isolated flurries, trace accumulation. Light to moderate west-southwest wind. Alpine high of -4C.

Avalanche Summary

The persistent weak layer was active last weekend, explosives triggered avalanches to size 2.5 and a cornice triggered a size 2 avalanche. On Sunday, wind redistributing new snow resulted in numerous natural wind slabs avalanches (size 1) noted in the region.

Snowpack Summary

Up to 20 cm of fresh snow is being redistributed around lee areas at treeline and alpine elevations. A combined total of 60-110 cm of recent snow has formed a slab that sits on a persistent weak layer that formed in early December. This layer mostly consists of facets (sugary snow) with some isolated areas also containing small surface hoar (feathery crystals). Several other weak layers have been observed in the lower snowpack such as crusts and facets that formed in late October/early November. With this weak basal snowpack, it is likely that an avalanche triggered on the persistent slab would step down to these lower layers, resulting in a full depth avalanche.

Avalanche Problems

Persistent Slabs

60-110 cm of snow sits on a weak layer consisting primarily of facets (sugary snow). Winds have redistributed recent snow and slabs may be more reactive in wind-loaded areas.
Be careful with wind loaded pockets, especially near ridge crests and roll-overs.Be wary of slopes that did not previously avalanche.Avoid convexities or areas with a thin or variable snowpack.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Unlikely - Possible

Expected Size: 1.5 - 2.5