Avalanche Canada mconlan, Avalanche Canada

North Rockies Avalanche Forecast

Jan 13th, 2020 2:00PM

The alpine rating is moderate, the treeline rating is moderate, and the below treeline rating is low. Known problems include Wind Slabs and Persistent Slabs.

Cold and clear is the forecast for the next few days. As you travel, watch for wind slabs in exposed terrain and a potential weak layer around sheltered treeline in the south of the region.

Summary

Confidence

Moderate - Uncertainty is due to how quickly the snowpack will recover and gain strength.

Weather Forecast

MONDAY NIGHT: Clear skies, light to moderate northeast wind, alpine temperature -35 C.

TUESDAY: Clear skies, light to moderate northeast wind, alpine temperature -35 C.

WEDNESDAY: Clear skies, light to moderate northeast wind, alpine temperature -32 C.

THURSDAY: Mostly cloudy with flurries, accumulation 1 to 3 cm, moderate east wind, alpine temperature -25 C.

Avalanche Summary

A few wind slabs were reported in the region over the weekend. They were in alpine terrain. Shooting cracks were also noted around treeline, suggesting that wind slab activity is possible at both treeline and alpine elevations.

The latest report of avalanche activity on the surface hoar layer described in the snowpack summary was from January 9. It occurred near the McGregors on a southerly aspect at 1500 m.

Snowpack Summary

Around 20 to 50 cm of storm snow has accumulated since late last week. This has created soft surface conditions in sheltered terrain but strong wind has redistributed the snow in exposed terrain, forming wind slabs. The wind changed directions from southwest to northeast over the weekend, meaning that wind-affected snow and wind slabs may be found on all aspects at and above treeline.

A weak layer of feathery surface hoar remains a concern. The layer has been found across much of the North Rockies region, but it has only become a problem in particular areas, such as around McBride and the McGregors. It may exist around sheltered treeline somewhere between 50 and 150 cm deep.

Terrain and Travel

  • Recent wind has varied in direction so watch for wind slabs on all aspects.
  • Be aware of highly variable recent wind loading patterns.
  • Surface hoar distribution is highly variable. Avoid generalizing your observations.
  • Back off if you encounter whumpfing, hollow sounds, or shooting cracks.

Problems

Wind Slabs

An icon showing Wind Slabs

Likelihood

Possible

Expected Size

1 - 2

Wind from variable directions has redistributed recent snow and formed wind slabs in exposed terrain. The most problematic terrain features include steep slopes near ridges. 

Aspects:

All aspects.

Elevations:

Alpine, Treeline.

Persistent Slabs

An icon showing Persistent Slabs

Likelihood

Possible

Expected Size

2 - 3.5

A weak layer of surface hoar may be found in parts of the region. There is uncertainty on where this layer is a problem, but it appears to be of highest concern in sheltered terrain features near treeline in the southern half of the region, particularly around McBride and the McGregors. It remains possible that humans could trigger this weak layer.

Aspects:

All aspects.

Elevations:

Treeline.

Valid until: Jan 15th, 2020 5:00PM