Avalanche Forecast

Issued: Jan 10th, 2018 6:48PM

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

ghelgeson, Avalanche Canada

South Coast Inland.

These ratings are biased toward the southern half of the region where deeper storm totals are expected. They reflect conditions that are expected to develop Thursday afternoon as new snow and wind create fresh storm slabs at upper elevations.

Summary

Confidence

Moderate - Timing, track, or intensity of incoming weather system is uncertain on Thursday

Weather Forecast

A significant weather system is expected to impact the Coast Thursday. Steady snow is expected throughout the day Thursday with light accumulations in the northern half of the region, more significant accumulations are expected to the south. A ridge of high pressure will start to build over the Pacific again starting Friday. On Saturday a stagnant airmass should allow warm air to begin spilling into the region. THURSDAY: Overcast, freezing level at valley bottom, moderate southwest wind, 5 to 10 cm of snow possible in the north of the region. 15 to 25 cm of snow expected in the south of the region.THURSDAY NIGHT: Overcast, freezing level at valley bottom, moderate to strong south/southwest wind, 5 to 10 cm of snow possible.FRIDAY: Scattered cloud, freezing level around 850 m, moderate to strong west/southwest wind, trace of snow possible.SATURDAY: Overcast, freezing level beginning near 1200 m, rising to 2600 m throughout the day, light southwest wind, no precipitation expected.

Avalanche Summary

No new avalanche activity was reported on Tuesday or Wednesday. On Monday isolated wind slabs above 2200 m were reactive to skier triggering, but were reluctant to move. On Sunday a small size 1 natural avalanche and a couple small skier controlled avalanches were reported from unknown aspects/elevations. These were likely small storm slabs running above the recently formed crust.

Snowpack Summary

20 to 40 cm of recent storm snow now rests on the the January 6th crust. This crust formed after temperatures cooled on Saturday, locking up the previously moist surface snow. On Sunday moderate to strong southwest winds redistributed snow and formed wind slabs in lee features at and above treeline. A widespread melt-freeze crust formed in mid-December is still an issue in the northern portion of the region where it is down 40 to 50 cm below the surface. Recent observations have shown that there are rounding facets underneath the crust on polar aspects (north and east) at and above treeline. Recent snowpack tests have produced easy sudden-planar results on solar aspects (south and west) at and above treeline on this interface as well. Around the Coquihalla this interface is not problematic and is thought to be part of a well bonded mid-pack. The lower snowpack is generally strong and well settled.

Problems

Storm Slabs

5 to 15 cm of snow near the Duffey and 15 to 25 cm of snow near the Coquihalla is expected Thursday with wind out of the south. Watch for the formation of fresh storm slabs which may be increasingly sensitive to human triggering throughout the day.

Avoid avalanche terrain during periods of heavy loading from new snow and wind.Closely monitor how the new snow is bonding to the old surface as you travel throughout your day.Be cautious in lee features above treeline, old wind slabs rest on a buried crust.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

1 - 2

Valid until: Jan 11th, 2018 2:00PM