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Avalanche Forecast

Archived

Apr 9th, 2023–Apr 10th, 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 fresh and reactive wind slabs forming where recent soft snow is available for transport. Seek out wind-sheltered terrain for the best turns.

Confidence

Moderate

Avalanche Summary

On Saturday a rider triggered a cornice fall from a distance, which produced a size 3 persistent slab avalanche on a northeast aspect at 1750 m. The avalanche was 200 cm deep and was suspected of having failed on the layer of facets above a crust buried in January.

On Friday a size 1 skier remote was reported on a north east facing slope at treeline. The avalanche was 40 cm deep and failed on a weak interface, possibly also a layer buried in January.

Snowpack Summary

20-30 cm of recent soft snow may have seen some redistribution by wind but is largely available for transport. The new snow sits over previously wind-affected snow on north and east facing slopes and a crust on south facing slopes. Lower elevations likely have a crust on or near the surface from recent warm temperatures.

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

Sunday night

Cloudy with 5-10 cm of new snow. Moderate to strong southerly winds. Alpine low -8 C.

Monday

A mix of sun and cloud with isolated flurries possible. Moderate southwest winds. Alpine high -7 C.

Tuesday

Mostly sunny. Light southwest winds. Alpine high -5 C.

Wednesday

A mix of sun and cloud. Moderate to strong southwest winds. Alpine high -7 C.

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.
  • Use caution on large alpine slopes, especially around thin areas that may propagate to deeper instabilities.
  • Pay attention to cornices and give them a wide berth when traveling on or below ridges.

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.