Avalanche Forecast

Issued: Dec 18th, 2013 8:32AM

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

ghelgeson, Avalanche Canada

Northwest Coastal.

Danger ratings will be one level higher in areas that receive more than 20 cm on Thursday.

Summary

Confidence

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

Weather Forecast

Synopsis: The pattern switches to a NW flow for the forecast period opening the door for some cooler dryer snow and potentially strong winds.Thursday: Freezing Level: 300m Precip: 10/15mm 10/20cm Wind: Mod, WestFriday: Freezing Level: 900m Precip: Trace Wind: Mod gusting Strong NWSaturday: Freezing Level: 500m Precip: 2/3mm 4/6cm Wind: Light, NW.

Avalanche Summary

Numerous size 2-3 avalanches have been running naturally and with explosive assistance throughout the region. Large avalanches have been running on all aspects, with the bulk of the activity occurring on N - SE facing aspects. The activity likely calmed down a bit on Wednesday as temperatures dropped.

Snowpack Summary

Heavy wet snow has fallen at upper elevations with freezing levels rising to 1500m during the last storm. Strong west winds have transported the new snow creating storm slabs that sit above a weak layer formed during the last cold snap. Surface hoar, and facets in the upper snowpack are now buried anywhere from 50 to 80cm from the surface by the recent stormShames area at 950m elevation suggested the mid and lower snowpack was composed of various faceted layers and a stiff 4 cm crust. Another crust can be found closer to the base of the snowpack. The recent precipitation will strengthen the snowpack at lower elevations, but may prove to be problematic with rapid wind loading at upper levels.

Problems

Storm Slabs

Stiff wind slabs, softer storm slabs and loose dry avalanches remain a concern as the region receives continued snowfall and NW winds. This problem will be most sensitive to human triggering in areas that have a crust down aprox. 50 cm.

Avoid all avalanche terrain during periods of heavy loading from new snow, wind, or rain.>Be cautious as you transition into wind affected terrain.>Minimize exposure during periods of heavy loading from new snow and wind.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 5

Deep Persistent Slabs

Various deeply buried weak layers are present in the region. As the region receives new snow and wind these weak layers may become more sensitive to both natural and human triggering.

Be aware of the potential for large, deep avalanches due to the presence of deeply buried weak layers.>Be aware of thin areas that may propogate to deeper instabilites.>Storm slab avalanches may trigger large deep avalanches.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 6

Valid until: Dec 19th, 2013 2:00PM