Avalanche Forecast

Issued: Dec 30th, 2017 4:55PM

The alpine rating is moderate, the treeline rating is moderate, and the below treeline rating is moderate. Known problems include Storm Slabs.

ghelgeson, Avalanche Canada

Sea To Sky.

Sunday offers one last day of cool temperatures before warming arrives Sunday night. Pay attention to how the snow feels underneath you, as the storm snow settles into a more cohesive slab it will likely become more sensitive to human triggering.

Summary

Confidence

Moderate - Freezing levels are uncertain on Monday

Weather Forecast

After a succession of snowstorms over southern BC, the weather over the lower mainland will settle into a dry period as 2017 comes to an end and 2018 begins. All indications point to the dry spell lasting until at least mid-week.SUNDAY: A few clouds, freezing level beginning at valley bottom with an Above Freezing Layer (AFL) forming between 1500 m and 2500 m in the late afternoon. Light northwest wind, no snow expected.MONDAY: Scattered cloud, freezing level rising to around 2500 m mid-morning, light variable wind, no snow expected.TUESDAY: Cloud cover increasing to overcast throughout the day, freezing level around 2500 m, light variable wind, no snow expected.

Avalanche Summary

On Friday control work produced storm and wind slabs averaging size 1.5 with crowns 10 to 40 cm in depth. Small loose dry avalanches were also reported on a moderately inclined southeast facing slope at 1500 m.

Snowpack Summary

Two successive storms produced 50 to 70 cm of storm snow with wind out the southwest, south and southeast that was strong at times. All of this new snow rests on a variety of old surfaces including crust on solar aspects, old wind slabs, facets and isolated surface hoar below treeline. As temperatures begin to warm late Sunday the storm snow will likely settle into a more cohesive slab. 40 to 100 cm below the surface there is a widespread melt-freeze crust that was buried on December 15th. This layer has not produced much in the way of avalanche activity, but could come to life as the overlying slab becomes more cohesive as temperatures warm. Beneath the December 15th layer, the lower snowpack is generally strong and well settled.

Problems

Storm Slabs

50 to 70 cm of new snow has fallen in the last few days accompanied by wind mainly out of the south. Human triggered avalanches may become more likely as time, warm temperatures and wind loading allow the snow to settle into a more cohesive slab.

Avoid wind loaded terrain at and above treeline, especially near ridge crests and roll-overs.As the storm slab problem gets trickier, the easy solution is to choose more conservative terrain.Avoid open slopes and convex rolls at and below treeline where buried surface hoar may be preserved.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

1 - 2

Valid until: Dec 31st, 2017 2:00PM