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Avalanche Forecast

Archived

Dec 29th, 2018–Dec 30th, 2018

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

Regions

Sea To Sky.

A more stable weather pattern is forecast for the next few days, however newly formed storm and wind slabs will need several days to settle and bond.

Confidence

Moderate -

Weather Forecast

SATURDAY NIGHT: Cloudy with isolated flurries and clear periods / Moderate northwest wind / Alpine temperature -6 CSUNDAY: Mostly cloudy with sunny breaks / Moderate northwest wind / Alpine temperature -7 C MONDAY: Mix of sun and cloud / Light north wind / Alpine temperature -5 CTUESDAY: Mainly Cloudy / Light west wind / Alpine Temperature -3 / Freezing level 700 m

Avalanche Summary

Recent avalanche activity has been reported as several explosives controlled size 2 storm and wind slabs in the alpine and tree line. Some of these avalanches were running on a layer of surface hoar buried around December 23. There was also a report of a size 3 wind slab avalanche that released sympathetically to an avalanche that was set of by an explosive about 30m away.

Snowpack Summary

40-50 cm of recent new snow sits on a weak layer of feathery surface hoar. Snow amounts will be deepest and touchiest in the lees of terrain features immediately adjacent to ridges.Below 1800 m, around 50 cm of storm snow may not be bonding well to an underlying crust (see here).A weak layer of sugary facets and surface hoar lies around 150 to 200 cm deep in the snowpack. There hasn't been reports of avalanches on this layer for over a week. That being said, this layer may still exist in isolated areas around treeline in some portions of the region.At the base of the snowpack, weak and sugary facets are found below an early-season melt-freeze crust. This weak layer has been the culprit for sporadic, very large avalanches in alpine terrain in the past few weeks. The avalanches have occurred in areas where the ground roughness is very smooth, for example glaciers, firn, and shale/rock slab slopes. An avalanche could be triggered in this layer with a very large trigger, such as a cornice fall.

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.