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Avalanche Forecast

Archived

Mar 23rd, 2023–Mar 24th, 2023

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, Tutshi, Wheaton, White Pass East, White Pass West.

Watch for new snow and southwest winds building fresh thin wind slabs that may be reactive to skier traffic in north and east facing terrain through the day.

Confidence

Moderate

Avalanche Summary

No new avalanches of note were reported in the region this week.

Backcountry users may see evidence of a large avalanche cycle from the weekend as they travel through the terrain. These avalanches may have occurred during last week's storm or due to solar input and elevated freezing levels through the weekend.

On Sunday, a suspected skier triggered avalanche was reported. This was a size 1 storm slab avalanche that likely occurred on Saturday.

If you head out in the backcountry, let us know what you are seeing by submitting a report to the Mountain Information Network.

Snowpack Summary

Warm temperatures and strong winds have redistributed 50 cm of storm snow creating hard wind affected surfaces in alpine and exposed treeline terrain. This overlies previously wind affected snow (sastrugi) in exposed areas and faceted snow in sheltered features.

Specific to Haines pass and below 1300 m the 50 cm of storm snow now has a stout and supportive melt freeze crust that has capped it. An additional 5 to 15 cm of new snow now overlies this melt freeze crust.

A buried weak layer of surface hoar can be found about 80 cm deep in Powder Valley, Tutshi, Paddy Peak and Haines pass areas, 150 to 200 cm around White Pass. This layer is most prominent on northerly slopes sheltered from the wind. On other aspects, this layer is a hard melt-freeze crust with weak facets around it. This layer has been most problematic in alpine terrain.

The remainder of the middle of the snowpack is consolidated and strong. Weak faceted grains are found near the base of the snowpack, particularly in thin snowpack areas.

Weather Summary

Thursday Night

Cloudy with light flurries, 1 to 5 cm accumulation. Strong southwest ridgetop winds easing to moderate . Alpine temperature low -8°C. Freezing levels valley bottom.

Friday

Cloudy with some afternoon clearing, isolated light flurries, 1 to 5 cm of accumulation. Light south ridgetop winds. Alpine temperature high -5°C. Freezing levels rising to 500 m.

Saturday

Cloudy with afternoon clearing, isolated very light flurries, trace to 1 cm of accumulation. Light south ridgetop winds. Alpine temperature high -6°C. Freezing levels rising to 300 m.

Sunday

Cloudy with afternoon clearing, no new precipitation. Moderate becoming strong north ridgetop winds. Alpine temperature high -7°C. Freezing levels rising to 200 m.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Fresh wind slabs will likely form throughout the day, diligently watch for changing conditions.
  • Be careful with wind slabs, especially in steep, unsupported and/or convex terrain features.
  • Avoid steep, rocky, and wind effected areas where triggering slabs is more likely.

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.

Persistent Slabs

Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.