Avalanche Forecast

Archived

Apr 6th, 2025–Apr 7th, 2025

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches possible, human triggered probable.

Below Treeline

Natural avalanches possible, human triggered probable.

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

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

Warm temperatures are expected to persist into Monday, limiting the overnight refreeze of the upper snowpack. Monitor local conditions and minimize exposure to bigger terrain until things cool off.

Areas east of HWY 93N and the Lake Louise backcountry have a thinner snowpack, making it more susceptible to human-triggering.

Confidence

Moderate

Avalanche Summary

Solar-triggered natural avalanches up to size 2 were occurring in steep terrain as the day heated up on Sat/Sun, occasionally gouging down into the lower snowpack.

A natural size 2.5 slab avalanche occurred Saturday in the early afternoon on a steep south aspect of Mt Jimmy Simpson. It was likely triggered by a sluff and failed on the January facets.

Several cornice failures have also been observed later in the day, occasionally triggering slabs up to size 2.

Snowpack Summary

Light wind effect in the alpine. On alpine north aspects, 15-30 cm of dry settled snow sits over the Mar 27 crust that exists to ~2500 m. On solar aspects sun crusts are present to ridgetop with moist snow later in the day. A supportive surface crust exists in most places below treeline.

A 30-70 cm firm midpack overlies the weak January facets and basal depth hoar which remain a concern.

Treeline snowpack depths range from 100 to 150 cm.

Weather Summary

Air temps and solar inputs are key things to pay attention to as we move into spring.

Sunday night: Becoming cloudy. Alpine temps remain near 0°C with minimal refreeze overnight. Ridge wind light to 25 km/h. Freezing level staying around 2400 m.

Monday: Mainly cloudy with light precip beginning in the late afternoon. SW winds in the moderate range. Treeline temps near +2°C with freezing levels staying around 2400 m.

Terrain and Travel Advice

Avalanche danger will increase as the surface crust breaks down.
Avoid steep, sun-exposed slopes when the air temperature is warm or when solar radiation is strong.
Start your day early and be out of avalanche terrain during the heat of the day.
Be mindful that deep instabilities are still present and have produced recent large avalanches.

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.

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.