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Avalanche Forecast

Archived

Dec 25th, 2020–Dec 26th, 2020

Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Below Threshold.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely.
Below Treeline
Below Threshold.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely.
Below Treeline
Below Threshold.

Regions

Yukon.

Triggering wind slab avalanches is a possibility with the fresh powder and uncertainty about if, when, and where wind has affected the snow.

Confidence

Moderate - Uncertainty is due to the speed, direction, or duration of the wind and its effect on the snowpack.

Weather Forecast

A weak low pressure system will bring some light flurries Friday night and Saturday morning and then clearing weather into Sunday.

FRIDAY NIGHT: Isolated flurries with 1-3 cm of snow, light northeast wind, temperatures around -10 C.

SATURDAY: Isolated flurries continue with trace amounts of snow, light northeast wind, temperatures around -10 C.

SUNDAY: Mix of sun and cloud, light south wind, temperatures around -8 C.

MONDAY: Isolated flurries with trace amounts of snow, light southwest wind, temperatures around -6 C.

Avalanche Summary

No recent avalanches have been reported. Cold calm conditions have likely limited the formation of new wind slabs, however older wind slabs obscured by the new snow are still a concern. Until the next uptick in wind, the most likely place to trigger an avalanche is still on the leeward side of ridges and ribs where wind slabs most often form. Don't allow the low density surface snow to cloud your assessment of these buried hazards.

Snowpack Summary

Weather stations suggest there has been little wind at White Pass since 30 cm of low density snow fell on Wednesday. This suggests there should still be fresh powder in most areas, but I wouldn't be surprised if there has been (or will be) some localized drifts forming soft wind slabs. Buried wind slabs beneath the powder also remain a concern.

A widespread melt-freeze crust now exists at an estimated 60-80 cm deep in the region, under our recent storm snow layers. This crust has been reported up to 1400 m in the Wheaton Valley and up to 1800 m near the Alaska border. 

The lower snowpack is generally settled and strong after a big storm at the beginning of December. However, there is potential for weak snow to persist at the bottom of the snowpack in colder, thinner snowpack areas such as the Wheaton Valley. 

Terrain and Travel

  • Be careful with wind loaded pockets, especially near ridge crests and roll-overs.
  • Avoid terrain traps where the consequence of any avalanche could be serious.
  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.

Problems

Wind Slabs

Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.