Avalanche Forecast

Archived

Feb 20th, 2023–Feb 21st, 2023

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches possible, human triggered probable.

Below Treeline

Natural avalanches unlikely.

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely.

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely.

Regions

Jasper, Brazeau, Churchill, Cirrus-Wilson, Fryatt, Icefields, Maligne, Marmot, Miette Lake, Pyramid.

New snow and a change to northeasterly winds will create new wind slabs at ridge crest on southerly aspects. We are expecting continued natural wind slab and deep persistent slab avalanche activity.When assessing your ski objectives, look for overhead hazards such as large alpine bowls, cornices, or cross loaded slopes. Choose terrain conservatively and bear in mind the potential for a low probability high consequence avalanche occurrence.

Confidence

Moderate

Avalanche Summary

Parkway patrol on Sunday observed isolated large natural deep persistent slab avalanches up to size 2.5 in the alpine - 2 had stepped down to the basal facets.

Late report from Shangrila area of a large avalanche off Mnt Jeffrey reaching the creek likely on Feb 16.

Don't forget to post avalanche observations to the MIN.

Snowpack Summary

New snow from overnight Monday will be sitting on wind slabs in the alpine and exposed tree line formed by recent strong to extreme southwesterly winds. In sheltered locations the upper snowpack is comprised of 30cm settled snow from the past couple of weeks on top of a generally weak mid and lower snowpack with facets and depth hoar at the base. The height of snow is variable from 50 to 150cm.

Weather Summary

We are expecting up to 15cm new snow by Tuesday morning throughout the bulletin region. The Arctic airmass will descend and push the active low pressure to the south on Tuesday. Winds will be light overnight switching to moderate values from the northeast in the morning. Temperatures will plummet below seasonal values with isolated flurries continuing into Wednesday.

Detailed weather forecasts from Avalanche Canada: https://avalanche.ca/weather/forecast

Terrain and Travel Advice

Expect slab conditions to change drastically as you move into wind exposed terrain.
Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.

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.

Deep Persistent Slabs

Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.