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Avalanche Forecast

Archived

Apr 14th, 2023–Apr 15th, 2023

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

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

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 soft snow may have seen some redistribution by recent wind but above 1200 m, it remains largely available for wind transport. Below 1200 m, moist snow or a thin crust may exist at or near the surface.

The new snow sits over previously wind-affected snow on north and east facing slopes and a crust on south facing slopes.

A weak layer of surface hoar/crust/facets buried in early January is now buried over 1 m deep in most areas. This layer has produced recent avalanche activity and remains a concern in terrain where the snowpack is thin. The lower snowpack consists of basal facets, particularly in shallow areas.

Weather Summary

Friday Night

Mostly cloudy / 20 km/h east ridgetop wind / Temperature at treeline around -5 C / Freezing level valley bottom

Saturday

Mix of sun and cloud with isolated flurries; 0-10 cm, then another 3-15 cm overnight / 20 km/h southeast ridgetop wind / Temperature at treeline around -3 C / Freezing level 1100 m

Sunday

Mix of sun and cloud / 10 km/h east ridgetop wind / Temperature at treeline around -3 C / Freezing level 1100 m

Monday

Cloudy with isolated flurries; 0-3 cm / 10 km/h northwest ridgetop wind / Temperature at treeline around -4 C / Freezing level 800 m

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Avoid steep, rocky, and wind effected areas where triggering slabs is more likely.
  • Cornice failure may trigger large avalanches.
  • Use caution on large alpine slopes, especially around thin areas that may propagate to deeper instabilities.

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.