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Avalanche Forecast

Archived

Feb 2nd, 2024–Feb 3rd, 2024

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

Regions

Northwest Coastal, Northwest Inland, Boundary, Stewart, Kispiox, Ningunsaw, Ningunsaw, Ningunsaw.

Avalanche danger will decrease as temperatures cool but wind slabs remain triggerable at upper elevations.

Be sure to verify conditions by making observations as you travel.

Confidence

Moderate

Avalanche Summary

A very large natural avalanche cycle, size 2.5-3.5 was observed this week, with the most recent occurrence near Ningunsaw on Friday. These large avalanches included a combination of fresh wind slabs and persistent slabs failing on buried weak layers. Most were triggered in alpine start zones, entrained wet snow and ran far, many to valley bottom.

By Friday, most avalanche activity was trending smaller; size 1 rider-triggered wind slabs on north to east aspects.

Snowpack Summary

A moist upper snowpack up to 1800 m is refreezing into a crust as temperatures cool. In the alpine, overlying dry wind slabs may slow the refreeze.

Various layers formed in January are now buried 50-100 cm deep. Up to 1600 m this presents as a thick crust, and at higher elevations, facets, sometimes in combination with surface hoar. Large avalanches ran on these layers during the height of the recent warm, wet storm. It is expected that they will strengthen as temperatures drop.

Below treeline, the majority of the snowpack is rain-soaked and starting to refreeze. It diminishes rapidly to dirt below 500 m.

Weather Summary

Friday night

Partly cloudy with up to 5 cm of snow. Southwest ridgetop wind 30-40 km/h. Freezing level at valley bottom. Treeline low around -11 °C. Freezing level drops to valley bottom.

Saturday

Mostly sunny. West ridgetop wind 30-40 km/h. Treeline temperature around -10°C.

Sunday

A mix of sun and cloud. Northwest ridgetop wind 10-20 km/h. Treeline temperature around -8 °C.

Monday

Sunny. Northeast ridgetop wind 20-30 km/h. Treeline temperature around -10 °C.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Be careful with wind slabs, especially in steep, unsupported and/or convex terrain features.
  • If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
  • Use extra caution around cornices: they are large, fragile, and can trigger slabs on slopes below.
  • Make observations and assess conditions continually as you travel.

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.