Avalanche Forecast

Moderate - Uncertainty is due to the timing, track, & intensity of the incoming weather system. Uncertainty is due to whether buried persistent weak layers become active, triggering avalanches, with the arrival of the forecast weather.

Stormy weather continues through the weekend with heavy precipitation and a windy double system for Friday and Saturday. In general, the Coquihalla pass area is forecast to receive higher snowfall amounts than the northern Cayoosh pass region or southern Manning park area.  

Thursday night: Mainly cloudy with scattered snow flurries, trace to 5 cm new snow, light to moderate southwesterly ridge top wind, alpine low -4 C, freezing level 700 m. 

Friday: Mainly cloudy with snow flurries and heavy snow later in the day, (up to 30cm expected for the Coquihalla and 15 cm elsewhere), wind increasing to moderate southwesterly gusting extreme, alpine high 0C, alpine low -3C, freezing level 1200 m and rising to 1700m late in the day. A significant frontal system is forecast to pass through the Coquihalla pass area Friday afternoon bringing extreme SW winds, heavy bands of precipitation and rapidly rising freezing levels.

Saturday: Continued snow with an additional 10-20 cm new snow in the early morning, moderate southwesterly ridge top winds gusting strong, alpine high 0C, alpine low -4C, freezing level dropping to 1200m.

Sunday: Heavy precipitation with a mix of snow and rain, up to 30cm/mm expected in the Coquihalla pass area tapering to trace amounts in the north. Moderate southwesterly ridgetop wind gusting extreme, alpine high +4C, alpine low -4C, freezing level expected to rise as high as 2100m.

Limited observations from this region have been reported during the previous days of stormy weather. Forecast heavy snow (20-35cm) and strong to extreme southwesterly winds will be creating heightened avalanche conditions over the day Friday in the Coquihalla Pass area. In other regions (near Manning Park and in the Duffy) less overall snowfall and wind values will keep hazard considerable.  

On Sunday and Monday, MIN reports described skier triggered wind slabs size 1-1.5, 20-30 cm deep on steep, north facing slopes in both the Duffey (controlled) and Coquihalla (accidental skier triggered). This MIN From Nak & Thar on Monday reported ski cutting wind slab avalanches 15-20cm deep near ridgetop in immediate lee features. 

Have you been out and about in the mountains? If so please submit your observations to the Mountain Information Network (MIN). It doesn't have to be technical - photos are especially helpful! Thank you so much for all the great MINs submitted so far! 

A rain crust from the first week of December is down 55-75cm and remains the chief layer of concern in this area. It continues to produce intermittent test results and we are curious how it will react to additional snow loads.

The south coast inland has seen a series of storms deliver 5-15cm of new snow daily for the past few days. In the Duffy and Manning park areas this has resulted in about 50cm of snow while at the Coquahalla Pass area there is around 75cm of recent snow. Recent warm temperatures have settled the snowpack.  

Much of this snow arrived with moderate to strong winds, resulting in wind redistribution and wind loading in the lee features of ridgecrests. Strong southwesterly winds will form reactive windslabs in the alpine, at ridgecrest and in lee features.  

In the north of the region, a crust/facet layer sits near the ground. The most recent avalanche activity observed on this layer was on December 1st when a natural cornice fall triggered a size 3. More recent snowpack tests in the Cayoosh zone found this layer down 100+ cm and unreactive. While our uncertainty around the reactivity of this crust is keeping it on the radar going into the active weather pattern over the next week or so, it does not appear to be an active problem at this time.

• Minimize exposure during periods of heavy loading from new snow and wind.
• Storm snow and wind is forming touchy slabs. Use caution in lee areas in the alpine and treeline.
• Potential for wide propagation exists, fresh slabs may rest on surface hoar, facets and/or crust.
• Closely monitor how the new snow is bonding to the crust.