Avalanche Forecast

Issued: Dec 17th, 2015 7:44AM

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

Avalanche Canada triley, Avalanche Canada

The new storm was delayed but has arrived. Forecast wind and new snow will increase avalanche danger.

Summary

Confidence

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

Weather Forecast

The overnight snow did not happen for Thursday morning, but the wind was strong all day and snow started to fall during the day. Snow and strong southerly winds are forecast overnight. Expect 10-15 cm by Friday morning at treeline. Light snow and moderate winds during the day Friday. Flurries or light snow Saturday morning with increasing wind and snow in the afternoon. Strong southerly winds overnight with another 10-15 cm by Sunday morning and another 5-10 cm during the day.

Avalanche Summary

One size 2.0 natural wind slab was reported from Wednesday east of Terrace in the Skeena valley at about 1400 metres. New storm slabs are expected to develop with the incoming storm.

Snowpack Summary

Strong winds moved into the south of the region on Thursday ahead of the forecast storm. Outflow winds were limited on Wednesday to below 400 metres and did not transport much snow or destroy new surface hoar. The surface hoar layers are getting difficult to track by name, so lets talk about them by burial date. There is a new surface hoar layer developing now that has not been buried yet, but that should happen tonight. The forecast new snow and wind are expected to add to the load above the December 14th surface hoar (151214 SH) which was reported to give easy compression test results today with a sudden planar fracture character (CTE SP). This means that as a slab develops above this layer, it may allow for long fracture propagations resulting in larger avalanches. At this time there is 15-25 cm above the 151214 layer in the Shames area. The early December layer buried on the 1st or 2nd (151201 SH) is now down a metre or so depending on your area. This layers distribution is variable. In some areas, this layer may be sensitive to human triggering and wide propagations while in other areas it is non-existent or has gained significant strength.

Problems

Storm Slabs

An icon showing Storm Slabs
New storm slabs were delayed as the storm did not push inland as fast as forecast. Strong winds and new snow should develop storm slabs overnight.
Be cautious as you transition into wind affected terrain.>Minimize exposure during periods of heavy loading from new snow, wind.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 3

Persistent Slabs

An icon showing Persistent Slabs
Loading from wind and new snow continues above the early December surface hoar. This layers distribution varies across the region. 
Avoid open slopes and convex rolls at and below treeline where buried surface hoar may be preserved.>Carefully evaluate terrain features by digging and testing on adjacent, safe slopes.>

Aspects: All aspects.

Elevations: Alpine.

Likelihood

Unlikely - Possible

Expected Size

2 - 4

Valid until: Dec 18th, 2015 2:00PM