Avalanche Forecast

Archived

Apr 12th, 2024–Apr 13th, 2024

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

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

Clearing is forecasted for the weekend, making it a good time for alpine objectives. Start early and finish early.

The ski quality has slightly improved with small amounts of new snow over the last 24 hours. Expect evidence of widespread wind affect from earlier in the week.

Travel conditions are generally very good.

Confidence

Moderate

Avalanche Summary

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.

Avalanches reported on Thursday were two cornice triggered size 2.5's on N and E aspects of Mount Shanks (~72 hours old) and a cornice triggered size 3 slab on a NE and SE aspect at 2800m above Bow Lake. Failure planes are the Feb 3rd interface.

Snowpack Summary

Up to 15cm of new snow in the last 24 hours overlies crusts on solar aspects, and up to ~2000 m on north aspects. Above this the snow surface is dry, wind-affected snow. The upper snowpack contains several buried crusts.

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

Friday night: Clear periods, alpine temperature low of -5°C, mainly light ridge wind, gusting to 35km/h

Saturday: Mix of sun and cloud, alpine temperature high of 2°C, mainly light ridge wind, gusting to 35km/h and freezing level up to 2400m

Sunday: Mix of sun and cloud, alpine temperature high of 4°C, mainly light ridge wind, gusting to 30km/h and freezing level up to 2600m

Terrain and Travel Advice

Watch for wind-loaded pockets especially around ridgecrest and in extreme terrain.
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.