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Avalanche Forecast

Archived

Apr 15th, 2023–Apr 16th, 2023

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

Lingering wind slabs may remain reactive to human triggers on lee aspects in the alpine.

Avoid steep, rocky, and wind affected areas where triggering slabs are more likely.

Confidence

Moderate

Avalanche Summary

No avalanches were reported on Friday.

A size 3 persistent slab avalanche was reported on a southeast aspect in the alpine west of Kelsall lake on Thursday. It was suspected to have been triggered by solar radiation.

Observations are limited at this time of year, please consider sharing any information or photos you have on the Mountain Information Network to help guide our forecasts.

Snowpack Summary

20-30 cm of recent snow and light to moderate south wind may have formed wind slabs in isolated lee features in the alpine.

The recent snow sits over previously wind-affected snow surfaces on northerly aspects and sun crust on other aspects.

A weak layer of surface hoar/crust/facets buried in early January is now around 100 cm down in most areas. Operators continue to monitor this layer. A significant warming event or a large trigger (like a falling cornice) are the most likely things to activate this layer.

Weather Summary

Saturday Night

Partly cloudy with isolated flurries; 0-10 cm / 20 km/h south ridgetop wind / Temperature at treeline around -8 C / Freezing level valley bottom

Sunday

Mix of sun and cloud with isolated flurries; 0-10 cm / 10 km/h east ridgetop wind / Temperature at treeline around -4 C / Freezing level 900 m

Monday

Mix of sun and cloud / 10 km/h northwest ridgetop wind / Temperature at treeline around -4 C / Freezing level 800 m

Tuesday

Snow; 10-15 cm / 20 km/h northeast ridgetop wind / Temperature at treeline around -2 C / Freezing level 1100 m

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Avoid freshly wind loaded terrain features.
  • Avoid steep, rocky, and wind effected areas where triggering slabs is more likely.
  • Cornice failure may trigger large avalanches.

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.