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Avalanche Forecast

Archived

Dec 5th, 2019–Dec 6th, 2019

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

Regions

Sea To Sky.

Human triggered avalanches are likely in alpine terrain due to significant amounts of new snow and wind.

Confidence

High - We are confident the likelihood of avalanche will increase with the arrival of the forecast weather.

Weather Forecast

THURSDAY NIGHT: 10-25 cm of snow above 1600 m (rain below), 50 km/h wind from the southwest, alpine temperatures around -3 C.

FRIDAY: 10-20 cm of snow above 1800 m (rain below), 50 km/h wind from the southwest, alpine high temperatures around -1 C.

SATURDAY: 20-30 cm of snow above 1400 m (rain below), 30 km/h wind from the southwest, alpine high temperatures around -3 C.

SUNDAY: Mix of sun and cloud, light wind from the north, alpine high temperatures around -3 C.

Avalanche Summary

Heavy snowfall on Thursday night could result in a natural cycle of avalanches overnight and leave storm slabs primed for human triggering on Friday. Prior to the storm there were reports of a few small (size 1) slab avalanches triggered by skiers and explosives on Wednesday. They were 20-30 cm thick and ran on a hard crust. This crust could provide a bed surface for large avalanches to run on during the storm.

Snowpack Summary

A return to stormy weather is bringing much needed snow to the Sea to Sky region. 20-40 cm of new snow is possible by midday Friday, with another storm pulse coming Friday night. Not to far beneath this new snow is a hard crust that formed in late November. Recent snowpack tests have shown the snow above this crust is weak and could provide a bed surface for avalanches to run on. Typical snowpack depths in the alpine currently range between 50 and 150 cm, depending on the amount of wind affect. Snowpack depths taper quickly with elevation as most treeline terrain is still below the threshold for avalanches.

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.