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North Rockies Avalanche Forecast - March 18, 2021

Southwesterly winds continue to form wind slabs on lee and cross-loaded terrain features in the alpine. Use caution when transitioning into wind affected terrain and avoid wind loaded slopes below ridgetops.
North Rockies Avalanche

Southwesterly winds continue to form wind slabs on lee and cross-loaded terrain features in the alpine. Use caution when transitioning into wind affected terrain and avoid wind loaded slopes below ridgetops.

Thursday

Alpine - Moderate
Treeline - Moderate
Below treeline - Low

Friday

Alpine - Moderate
Treeline - Moderate
Below treeline - Low

Saturday

Alpine - Moderate
Treeline - Low
Below treeline - Low

Avalanche Summary

A few naturally triggered size 2 wind slabs on northerly aspects in the alpine were reported on Tuesday.

Our field team found some large and disturbingly wide avalanches in the Hasler last week, with lots of compelling images in their MIN report. It's suspected that these are running on facets that are about 80 cm below the surface.

Snowpack Summary

The northern portion of the region around Pine Pass got around 35 cm. of snow last weekend, but much less fell in the rest of the region. Southwesterly winds have formed wind slabs on lee and cross-loaded features below alpine ridgetops.

Sun crust exists on solar aspects and a temperature crust may exist on all aspects up to 1800 m. Large cornices are present throughout the region and are capable of triggering large avalanches when they fail. Cornice failures are most common during windy or warm weather.

About a metre of snow covers a weak layer of facets buried mid-February. Slightly deeper there is a widespread persistent weak layer from late January/early February that consists of surface hoar. It is most prevalent around treeline elevations, but likely reaches into the alpine and in openings below treeline too. These layers are both significantly shallower in the east of the region. Steep, rocky slopes with a shallow or thin to thick snowpack in the alpine and steep, open slopes at treeline are the most likely places to trigger these persistent weak layers. Large loads such a cornice falls or multiple sleds on the same slope often trigger slopes that single rider couldn't trigger.

Weather Forecast

THURSDAY: Increasing cloud in PM, then 5-10 cm. overnight / Strong, southwest ridgetop wind / alpine high temperature 0 / Freezing level 1900 m.

FRIDAY: Mix of sun and cloud / Strong, southwest ridgetop wind / alpine high temperature -2 / Freezing level 1500 m.

SATURDAY: Mix of sun and cloud / Moderate, northwest ridgetop wind / alpine high temperature -9 / Freezing level 800 m.

Travel and Terrain Advice

  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Avoid lee and cross-loaded terrain.
  • Avoid slopes that sound hollow or drum-like.
  • Be aware of the potential for large avalanches due to the presence of a deep persistent slab.