Avalanche Forecast

A warm front crossing the region is aimed to hit the Coquihalla the hardest.

SATURDAY NIGHT: Scattered flurries with 5 cm of snow for most parts of the region (except 10-15 cm in the Coquihalla), strong southwest wind, freezing level climbing to 1000 m with treeline temperatures around -3 C.

SUNDAY: Scattered flurries with another 5 cm of snow for most parts of the region (except for another 10-15 cm in the Coquihalla), strong to extreme southwest wind, freezing level climbing to 1400 m with treeline temperatures reaching -2 C.

MONDAY: 10 cm of snow in the north and 20-30 cm in the south, strong southwest wind, treeline temperatures drop to -4 C.

TUESDAY: Mostly cloudy with scattered flurries and up to 5 cm of snow, moderate west wind, treeline temperatures around -6 C.

The main story on Sunday will be new storm and wind slabs with the incoming storm. On Friday, the beginning of the storm already resulting in some small (size 1) reactive wind slabs in the Coquihalla (see MIN reports here and here). 

Last weekend there were several reports of large (size 2-3) natural wind slab avalanches across the region, as well as some human triggered avalanches such as this notable avalanche on in the Duffey (MIN report). Another notable size 3 (very large) persistent slab was remotely triggered by skiers at McGillivray Pass on Feb 8. This occurred on a southwest aspect at 2400 m and was described as a hard wind slab formed over our facet layer from late January.

Forecast snowfall amounts are variable across the region with only 5-10 cm for most parts of the region except for the Coquihalla where 20-30 cm is possible.  

The new snow adds to 15 cm of recent snow sitting above a potentially reactive interface consisting a sun crust on steep south slopes and faceted snow on polar aspects. In many areas there are old buried wind slabs that have become hard and mostly unreactive. These wind slabs were deposited in unusual places after a strong bout of northeast wind last week.

Persistent weak layers have trended towards being unreactive and vary by location within the region:

• In the south, the primary feature is a crust from mid-January in the Allison Pass area that is 40-60 cm deep. This layer is present in the Coquihalla snowpack (60-80 cm), but has been less problematic recently.
• In the north, the old wind slabs discussed above were reactive to skier triggering last week as they rested above early Feb interfaces of surface hoar (think shaded aspects) and sun crusts (think solar aspects). 
• Also in the north, older weak layers may still linger in shallow rocky terrain. This includes an old layer of faceted snow (Jan 24) roughly 50-70 cm deep and a crust from early December 100-200 cm deep. These deeper layers have not been reactive recently.

• Choose simple terrain.
• Watch for fresh storm slabs building throughout the day.
• Avoid all avalanche terrain during periods of heavy loading from new snow, wind, or rain.
• Dial back your terrain choices if you are seeing more than 20 cm of new snow.
• Avoid freshly wind loaded terrain features.