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Avalanche Forecast

Archived

Apr 21st, 2025–Apr 22nd, 2025

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.

Recent large, natural avalanche activity indicates an unstable snowpack in northerly alpine terrain.

Stick to lower-angled slopes and avoid overhead hazard.

Confidence

Moderate

Avalanche Summary

On Sunday in Haines Pass, several large natural persistent slab avalanches were reported from northerly alpine terrain. See full details in this MIN report.

Northerly alpine terrain will continue to be the main concern on Tuesday for both persistent slab avalanches and newly formed, reactive wind slabs.

Thank you for sharing your observations!

Snowpack Summary

Surface hoar (5-10 mm) has been reported to ridgetop in the Haines Pass.

At lower elevations and on south aspects, a crust can be found on the surface. On higher north aspects, new snow and southerly wind may continue to form wind slabs.

A weak layer of facets on a crust down 45 cm has produced recent, large natural avalanches in Haines Pass. Check out this MIN for details.

Weather Summary

Monday night

Cloudy with up to 5 cm of new snow. 30 to 50 km/h southwest ridgetop wind. Treeline temperature -4 °C. Freezing level 600 m.

Tuesday

Cloudy with up to 3 cm of new snow. 30 to 40 km/h southwest ridgetop wind. Treeline temperature -1 °C. Freezing level rises to 1000 m.

Wednesday

Cloudy with up to 5 cm of new snow. 40 to 70 km/h south ridgetop wind. Treeline temperature 0 °C. Freezing level rises to 1200 m.

Thrusday

Cloudy with up to 5 cm of new snow. 30 to 50 km/h south ridgetop wind. Treeline temperature 0 °C. Freezing level rises to 1200 m.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Be aware of the potential for large avalanches due to buried weak layers.
  • Cornice failures could trigger large and destructive avalanches.
  • Watch for newly formed and reactive wind slabs as you transition into wind-affected terrain.

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.

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.