Avalanche Canada mconlan, Avalanche Canada

North Rockies Avalanche Forecast

Jan 10th, 2020 2:00PM

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

New snow and variable wind will form wind slabs in exposed terrain on all aspects. Caution is also warranted in sheltered terrain features, as a buried weak layer could still be triggered.

Summary

Confidence

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

Weather Forecast

FRIDAY NIGHT: Cloudy with light snowfall, accumulation 2 to 5 cm, light to moderate west wind, alpine temperature -16 C.

SATURDAY: Cloudy with light snowfall, accumulation 2 to 5 cm, light to moderate northwest wind, alpine temperature -22 C.

SUNDAY: Mix of sun and cloud, light northeast wind, alpinee temperature -30 C.

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

Avalanche Summary

A few large, destructive were recently reported near the McGregors, suspected to have failed naturally on the weak layer described in the snowpack summary. They occurred on southerly aspects and at an elevation of 1500 m.

A few storm slab avalanches were also reported to have failed from human activity in recent storm snow.

Snowpack Summary

Around 10 to 20 cm of new snow may accumulate from Friday to Saturday. This will create relatively soft conditions in sheltered terrain but potentially wind slabs in exposed terrain. The wind will change directions from the southwest to the northeast by Sunday, meaning that wind slabs may be found on all aspects.

The main layer of concern is a feathery surface hoar layer that was buried around Christmas. The depth of this layer varies and could be found from about 50 cm deep to 150 cm deep. While this layer was very reactive last week, recent reports suggest that its reactivity is localized to certain parts of the region. There has been more recent evidence of this problem in the southern parts of the region around McBride and the McGregors, but preserved surface hoar could potentially be found on sheltered slopes anywhere in the region.

Terrain and Travel

  • Avoid freshly wind loaded features, especially near ridge crests, roll-overs and in steep terrain.
  • Surface hoar distribution is highly variable. Avoid generalizing your observations.
  • Be aware of the potential for large avalanches due to the presence of a persistent slab.
  • Back off if you encounter whumpfing, hollow sounds, or shooting cracks.
  • Choose gentle slopes without steep terrain above.

Problems

Wind Slabs

An icon showing Wind Slabs

Likelihood

Possible-Likely

Expected Size

1 - 2

Wind from variable directions is forecast, meaning that you may find new wind slabs on all aspects. The most suspect terrain will be exposed slopes near ridges at treeline and alpine elevations.

Aspects:

All aspects.

Elevations:

Alpine, Treeline.

Persistent Slabs

An icon showing Persistent Slabs

Likelihood

Possible

Expected Size

2 - 3.5

A touchy 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 in openings below treeline, at treeline, and in lower alpine elevations in the southern half of the region. Best to treat any steep slope in sheltered terrain as suspect.

Aspects:

All aspects.

Elevations:

All elevations.

Valid until: Jan 13th, 2020 5:00PM