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Avalanche Forecast

Archived

Apr 23rd, 2023–Apr 24th, 2023

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

Regions

Northwest Inland, Kispiox, Microwave-Sinclair, Ningunsaw, South Bulkley, South Bulkley, Telkwa.

Concern for triggering large persistent slab avalanches remains. Avoid steep, rocky, and wind-affected areas where triggering slabs are more likely.

Recent wind has varied in direction so watch for wind slabs on all aspects.

Confidence

Low

Avalanche Summary

No avalanches were reported on Saturday. However, observations in this region are currently very limited.

A naturally triggered size 2 wind slab was reported on a northeasterly aspect in the alpine on Thursday. See MIN.

Most professional operations are now closed which means we have very little snowpack or avalanche observation data. Please consider sharing any information or photos you have on the Mountain Information Network to help guide our forecasts.

Snowpack Summary

Recent wind has varied in direction so watch for wind slabs on all aspects.

A crust exists up to ridgetop on south-facing slopes and on all aspects up to approximately 1500 m.

A weak layer buried in late March is down 30-50 cm and exists as surface hoar or small facets on north facing slopes and a crust with small facets on top on sunny aspects. Test results show that this layer may be reactive to human triggers in isolated locations in the alpine where the layer is well-preserved. See MIN.

The middle of the snowpack is strong and contains numerous hard crusts. Near the ground, weak faceted crystals exist. There hasn't been avalanche activity on this layer recently, but it remains on our radar and may become active when we experience change, such as rapid loading (heavy snowfall or rain) or prolonged warming.

Weather Summary

Sunday Night

Cloudy with flurries; 0-15 cm (rain below 1000 m) / 30 km/h south ridgetop wind / Temperature at treeline around -1 C / Freezing level 1200 m

Monday

Mix of sun and cloud with isolated flurries; 0-3 cm (rain below 1000 m) / 30 km/h southwest ridgetop wind / Temperature at treeline around 0 C / Freezing level 1300 m

Tuesday

Mix of sun and cloud / 20 km/h southwest ridgetop wind / Temperature at treeline around -1 C / Freezing level 1200 m

Wednesday

Mix of sun and cloud with flurries; 5-10 cm (rain below 1000 m) / 50 km/h south ridgetop wind / Temperature at treeline around 1 C / Freezing level 1400 m

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Avoid steep, rocky, and wind effected areas where triggering slabs is more likely.
  • Watch for signs of instability like whumpfing, hollow sounds, shooting cracks or recent avalanches.
  • Potential for wide propagation exists, fresh slabs may rest on surface hoar, facets and/or crust.
  • Recent wind has varied in direction so watch for wind slabs on all aspects.
  • If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.

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.