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Avalanche Forecast

Archived

Apr 13th, 2024–Apr 14th, 2024

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

Regions

Banff Yoho Kootenay, Little Yoho, Banff, East Side 93N, Kootenay, Lake Louise, LLSA, Sunshine, West Side 93N, Field.

Heating and wind transport have triggered a few avalanches around the region over the last couple of days. Fresh slabs are evident and cornices are large.

While the winds are forecast to back off tomorrow, this may allow the sun to deliver more significant heating as freezing levels rise beyond what they have been for a while....

Confidence

Moderate

Avalanche Summary

Saturday on a response to the 93N, Visitor Safety observed a size 1.5 slab on the East of Dolomite Peak: up 40cm deep running on a crust (April2?) and a deep slab on the North side of Noseeum Mountain that failed to the ground sz 2 in the past 48-72hrs.

Friday, during a flight along Hwy 93N Fri Visitor Safety observed evidence of a size 2.5 wind slab avalanche stepping down to the Feb 3rd on Bow Peak (NE aspect) and several size 1.5's on similar terrain in the area.

Snowpack Summary

5 to 15 cm of snow in the past two days sits over a recent crust. Up to 50cm of snow sits on more extensive crusts from the start of April that go as high as 2200m on north aspects. Moist snow on steep solar slopes Saturday.

The midpack is generally well settled down to the February 3 persistent weak layer which remains a concern in shallow snowpack areas on northerly alpine aspects. In these areas, no crusts are found in the upper snowpack and the midpack remains thin and weak.

Weather Summary

Saturday night: Clearing. Winds SW 20-30 km/h. Freezing levels return to valley bottom.

Sunday: Winds diminish to light. Freezing levels rise to 2500m. Cloud builds in the afternoon. Partly cloudy overnight. Freezing levels drop to around 1900m overnight winds increase to 20-30km/h.

Monday: Freezing levels rise to 2000m. Increasing cloud in the afternoon with flurries or rain beginning late in the afternoon.

Terrain and Travel Advice

  • Watch for wind-loaded pockets especially around ridgecrest and in extreme terrain.
  • If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
  • Avoid thin areas like rock outcroppings where you're most likely to trigger avalanches failing on deep weak layers.

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.

Loose Wet

Loose Wet avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.