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Avalanche Forecast

Archived

Mar 26th, 2021–Mar 27th, 2021

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

Regions

Yukon.

Danger was on the rise Friday as fresh slabs formed with new snow at the high end of forecast amounts. More overnight snow and wind should keep slabs primed for human triggers on Saturday. Be ready to step back if snowfall exceeds the forecast. It wouldn't be the first time!

Confidence

Moderate - Forecast snowfall amounts are uncertain.

Weather Forecast

Friday night: Cloudy with continuing flurries bringing about 5 more cm of new snow. Moderate southwest winds.

Saturday: Cloudy with easing flurries bringing up to 5 cm of new snow, increasing again overnight. Light to moderate southwest winds, easing over the day and increasing, shifting north again overnight. Alpine high temperatures around -10.

Sunday: A mix of sun and cloud. Moderate to strong north winds easing over the day. Alpine high temperatures around -14.

Monday: Becoming cloudy. Moderate southwest winds. Alpine high temperatures around -10.

Avalanche Summary

Reports from the White Pass area over the midweek showed fairly minimal wind slab reactivity in areas where wind has actively been moving loose snow around. 

A rapid change in conditions was observed Friday morning as flurries and elevated winds initiated a new period of wind slab development. This pattern of light accumulation amid elevated, shifting winds should sustain through Saturday night.

Snowpack Summary

Light new snow amounts and elevated winds reignited wind slab formation in the White Pass area on Friday morning. Similar conditions will prevail through the first couple of days of the forecast period.

The new snow has mainly buried wind affected surfaces in exposed areas. Previous wind slabs have largely stabilized, but concern still exists for the ability of large triggers like cornices or machines to trigger older large, hard wind slabs in alpine areas that are now obscured by new snow.

There are no deeper concerns around White Pass.

Substantial spatial variability likely still exists in the snowpack around the Tutshi Lake/Paddy Peak area. Terrain here should be assessed on a slope by slope basis, as lingering snowpack weaknesses may still exist.

The Wheaton's continental snowpack is dominated by hard wind slabs overlying sugary facets and depth hoar. It's an untrustworthy snowpack structure that requires conservative terrain selection and diligent travel habits.

Terrain and Travel

  • Wind slabs are most reactive during their formation.
  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Avoid exposure to slopes that have cornices overhead.
  • In areas where deep persistent slabs may exist, avoid shallow or variable depth snowpacks and unsupported terrain features.

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.