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Avalanche Forecast

Archived

Apr 23rd, 2024–Apr 24th, 2024

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

Regions

Haines Pass.

Triggering large persistent slab avalanches may remain possible in specific alpine areas.

Avoid steep or convex slopes in the alpine where triggering slabs is more likely.

Confidence

Moderate

Avalanche Summary

No new avalanches were reported in this region on Monday.

Numerous slab avalanches up to size 2.5 were reported on a variety of aspects in the alpine on Saturday.

The slab avalanches likely failed on either a crust or a weak layer of surface hoar, depending on the aspect of the slope. Strong solar radiation often increases the likelihood of triggering both loose and slab avalanches. See MIN 1 and 2.

Snowpack Summary

A mix of wind affected and soft snow can be found in the alpine. Sunny aspects have a crust on the surface that may soften with daytime heating.

A few large slab avalanches were recently reported on a variety of aspects on steep alpine slopes. They likely failed on either a crust or a weak layer of surface hoar down 30 to 70 cm.

Cornices are large and looming at this time of year.

Weather Summary

Tuesday night

Mostly cloudy with isolated flurries, 0 to 5 cm snow. 5 to 10 km/h north ridgetop wind. Treeline temperature -4 °C. Freezing level 700 m.

Wednesday

Mix of sun and cloud. 10 to 20 km/h north ridgetop wind. Treeline temperature +3 °C. Freezing level 1600 m.

Thursday

Sunny. 10 to 20 km/h north ridgetop wind. Treeline temperature +4 °C. Freezing level 1700 m.

Friday

Sunny. 10 to 20 km/h southwest ridgetop wind. Treeline temperature +2 °C. Freezing level 1500 m.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Be aware of the potential for surprisingly large avalanches due to deeply buried weak layers.
  • Avoid steep convex slopes.
  • Be alert to conditions that change with elevation and sun exposure.
  • Cornice failures could trigger very large and destructive avalanches.
  • Back off slopes as the surface becomes moist or wet with rising temperatures.

Problems

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.