Avalanche Forecast

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The Pacific low pressure system will continue to be the dominant weather feature for a couple more days. For Tuesday overnight and Wednesday, 10-20mm of precipitation is expected in the wetter parts of the region. Alpine winds are expected to be moderate to strong from the southwest and freezing levels are forecast to be fluctuate between 400 and 700m. Thursday is expected to be unsettled as dry Arctic air replaces the Pacific low. 2-5mm of precipitation is forecast with sunny breaks in the afternoon. Freezing levels are expected to drop below valley bottom on Thursday night and remain there for the weekend. Dry and mostly sunny conditions are expected for Friday.

On Sunday, a skier triggered size 1.5 slab avalanche was reported from the Shames area. This occurred on a north aspect and propagated 25m across the slope running 150m in length. The avalanche released on a layer of surface hoar from the middle of November in an area with some wind affect. This layer may increase in reactivity with ongoing snowfall and wind loading from the stormy conditions.  If you are out in the mountains, please post your observations to the MIN.

Early season snowpack observations are still limited in the region but there is enough snow for avalanches above around 1000-1200m.  The average snowpack depth at treeline is reported to be around 1m and there are reports of over 1.5m of snow in the alpine. Surface snow tends to be variable with low density powder in sheltered areas, wind affected snow in exposed areas, and moist or wet snow at lower elevations. Recent strong southwest winds have likely formed wind slabs in leeward features at higher elevations. Buried surface hoar crystals up to 10mm have been found down 30-60cm. This layer has been reactive to snowpack tests, whumphing has been observed, and an avalanche was skier triggered on this layer on Sunday. This layer will likely continue to be a concern for the region with the ongoing storm loading increasing the slab thickness.  Dig down and test this layer before committing to big slopes. The mid pack is generally moist to ground with a series of crusts.