Avalanche Forecast

Archived

Apr 19th, 2024–Apr 20th, 2024

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, human triggered possible.

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.

Clear skies and warming temperatures Saturday will elevate the hazard.

For the most part, it is still very good travel for alpine objectives.

Start early, finish early.

Confidence

Moderate

Avalanche Summary

The recent cool temperatures have temporarily slowed down the deeper avalanche activity.

Over the last couple days in the alpine, some small thin, fresh windslabs and sluffs have been triggered in the surface snow.

On April 18th Visitor Safety had a flight West to the Lyell's and were able to see a wide swath of terrain. There has been a notable lack of avalanche activity of late.

Snowpack Summary

5-15 cm of settling, possibly moist snow overlies previous temperature crusts on E, W and S aspects. North aspects above 2200 m the recent snow overlays dry snow. Small wind slabs can be expected in specific areas in the alpine and will react easily to human triggers where on a smooth crust

In the mid-pack, the Feb 3 persistent layer (crust/facet layer) remains a concern on northerly alpine aspects, however, cooler temperatures have slowed down natural activity on this layer

Weather Summary

Friday night: Clear. Precipitation: Nil. Alpine temperature: Low -10 °C. Ridge wind light to 15 km/h. Freezing level at valley bottom.

Saturday: Clear. Alpine temperature: High 1 °C. Ridge wind south: 10-30 km/h from the South. Freezing level: 2300m.

Sunday: Flurries. Accumulation: 5-15 cm. Alpine temperature: High -4 °C. Ridge wind west: 20 km/h gusting to 80 km/h.

Terrain and Travel Advice

Watch for wind-loaded pockets especially around ridgecrest and in extreme terrain.
Wind slabs may be poorly bonded to the underlying crust.
Back off slopes as the surface becomes moist or wet with rising temperatures.

Problems

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.

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.