Avalanche Forecast

Continued Cool temperatures, with one more day of sun breaks before the next series of low pressures move through bringing cloudy conditions and scattered flurries.

Friday Night: Mainly cloudy, light and variable Northwesterly winds, freezing level valley bottom. Alpine Low -9C.

Saturday: Cloudy with sun breaks, light westerly winds, freezing level 800 m. Alpine High -7C.

Sunday: Cloudy with snow flurries, Accumulations Trace-4cm, light-moderate Southwesterly winds, freezing level 700 m. Alpine Low -10C / High -7C.

Monday: Cloudy with scattered snow flurries, Trace new snow accumulations, light Southwesterly winds, freezing level rising to 1000 m. Alpine Low -10C / High -7C.

Avalanche hazard remains quite variable and dependent on snowfall amounts, freezing rain intensity and freezing lines experienced during this recent storm. Certain regions received 40cm of snow while others barely saw 10cm. Most areas experienced high freezing levels, snow, then rain, then more snow. As conditions cooled, avalanche activity tapered.  

Lower hazard exists in areas with less overall snow fall and thicker rain crusts. This was reported at an isolated location in this MIN report from Nov 11, but does not exist for the entire region.

Initial reports were of the poor bond of the new snow to the rain crust, but this appears to be diminishing. Nonetheless, watch out and manage for "stuffing" or loose snow avalanches, particularly when transitioning to steeper terrain.  

Numerous reports from Wednesday have come in describing the poor bond of new snow to the recent rain crusts producing small to large avalanches 5-25cm deep. Skier controlled small avalanches are being reported in addition to explosive control small and large avalanches at tree line and in the Alpine.  

On Tuesday, at the peak of the cycle, reports of large avalanches (Size 2) naturally and from skier controlled and explosive control work on Tuesday. A few Very Large (Size 3) Natural avalanches were reported running to valley bottom along the highway corridor.  

Our eyes and ears in the mountains are limited this winter due to fewer professional observations. If you go out in the mountains, please share your observations on the Mountain Information Network (MIN). Photos are especially helpful! Thank you so much for all the great MINs submitted so far!

While there is a lot of variability across the forecast region in how the recent weather reworked the snowpack, the message is similar everywhere: Assess the bond of recent snow to crusts, especially if more than 20cm of snow is present. If there is not a thick rain crust at and below tree line then there is probably intact buried surface hoar.  

In many areas, freezing rain in the middle of the recent storm created this thick rain crust which thins with elevation up to 2300m. In some areas there are two rain crusts: a thin crust near the base of the recent storm snow and a second thicker (1-5cm) crust near the surface. 5-20cm of recent snow (higher levels to the far south) sits atop the smooth highest crust and is bonding poorly. See this MIN report from near Kokanee Glacier & this MIN report from the South Columbia near Hall Mountain. This MIN from backcountry near RMR reports a crust up to 2250m.

We know that prior to this storm there was a widespread large surface hoar. We know that heavy rains have made this layer no longer an issue in many areas. However, we suspect this layer may still be preserved in many tree line locations which were not as affected by high freezing levels and rain events. In other words, if there is no THICK rain crust at and below tree line, be on the look out for buried surface hoar. Check out this MIN report from Dec 10 of intact Surface Hoar at 1600m at a below tree line location from Glacier National Park. 

In the Alpine, recent winds will have redistributed snow. These storm slabs sit atop suncrust on solar aspects. As ever, steep solar slopes may deteriorate with direct sun triggering loose snow avalanches.  

Down near the ground remains a thick rain crust with sugary facets above and below from early November rains (Nov 5 Crust). While we have not seen much reactivity on this layer, it continues to produce occasional Hard results in snow tests. It is most likely to be reactive to human triggers on shallow rocky slopes in the alpine or tee line "alpine-like" features or be triggered by a step down avalanche.

• Investigate the bond of the recent snow before committing to your line.
• Watch for signs of instability like whumpfing, hollow sounds, shooting cracks or recent avalanches.
• Be careful with wind loaded pockets, especially near ridge crests and roll-overs.
• In areas where deep persistent slabs may exist, avoid shallow or variable depth snowpacks and unsupported terrain features.