North Rockies Avalanche Forecast - Feb. 27, 2020

Less snow fell than expected. However, avalanche danger will increase on Thursday with the incoming snow, wind, and mild temperatures. Monitor accumulations of new snow in your local riding area and reduce your exposure to avalanche terrain accordingly.

The North Rockies region encompasses the Rocky Mountains from Highway 16 in the south to Hudson's Hope in the north, spanning the BC-Alberta border. 

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Thursday

Alpine - Considerable
Treeline - Considerable

Below treeline - Moderate

Friday

Alpine - Considerable
Treeline - Considerable

Below treeline - Moderate

Saturday

Alpine - Consierable

Treeline - Moderate
Below treeline - Moderate

Avalanche Summary

No notable avalanches have been reported since the weekend when two large (size 2.5) persistent slab avalanches were reported on northeast slopes at Bijoux (see the Mountain Information Network report for photos). One appeared to be triggered by a snowmobile, while the other was triggered naturally by a cornice fall. Similar persistent slab avalanches were reported last week on buried surface hoar layers up to 100 cm below the surface.

Variable amounts of new snow over the coming days will develop new storm and wind slab avalanche problems that will be more dangerous in areas that receive heavier accumulations of new snow. In areas where buried surface hoar exists, triggering large persistent slab avalanches remains a concern. Cornices are also becoming an increasing concern with mild temperatures. 

Snowpack Summary

Between Monday and Friday anywhere from 15 to 50 cm of new snow is possible in the region. Areas with heavier accumulations will likely have widespread storm slabs, while areas with lighter accumulations will have more localized wind slabs. The new snow is accumulating above hard wind affected snow in open terrain and crusty snow at low elevations and on south and west facing slopes. Some of these interfaces could form sliding surfaces for the new snow.

Cornices will likely grow larger and could become fragile with the mild temperatures in the forecast.

The lower snowpack is strong in many parts of the region with two main exceptions:

A weak layer of surface hoar 50-80 cm below the surface has been a problem around treeline elevations at Pine Pass. The layer has also been observed in other parts of the region, such as Torpy, but seems to be less of a problem further south towards McBride. Although unlikely to trigger, an avalanche on this layer would be large.

Steep slopes where the snowpack is shallow and rocky could harbour weak basal facets

Weather Forecast

A series of frontal systems crossing the region Wednesday to Friday will deliver moderate to heavy snowfall to the region with strong wind and mild daytime temperatures.

WEDNESDAY NIGHT: 5-15 cm of snow along the western side of the continental divide and 2-5 cm along the eastern side, strong southwest wind, freezing level climbing to 1000 m with alpine temperatures around -5 C.

THURSDAY: Heavy snowfall in McBride and Kakwa (15-20 cm), moderate snowfall at Pine Pass and Torpy (10 cm), and light snowfall around Tumbler (5 cm), strong southwest wind across the region, freezing level climbing to 1200-1400 m with alpine temperatures reaching -2 C.

FRIDAY: Snowfall continues Thursday night and eases midday Friday with another 5-10 cm of snow, cloudy with sunny breaks in the afternoon, moderate southwest wind, freezing level rises to 1200-1400 m in the afternoon, alpine temperatures reaching -2 C.

SATURDAY: Current forecasts suggest an upslope storm could deliver up to 10 cm of snow to the eastern slopes of the region and less on the western slopes (stay tuned for more up-to-date forecasts), moderate northeast wind, freezing level drops back to valley bottom with alpine high temperatures around -7 C.

Travel and Terrain Advice

  • Dial back your terrain choices if you are seeing more than 20 cm of new snow.
     
  • Make conservative terrain choices and avoid overhead hazard.
     
  • Be aware of the potential for large avalanches due to the presence of buried surface hoar.
     
  • Use extra caution around cornices: they are large, fragile, and can trigger slabs on slopes below.
avalanche-forecast.26_12172.jpg
A map of the North Rockies. - Avalanche Canada image
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