Avalanche Forecast

Archived

Feb 19th, 2023–Feb 20th, 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 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.

Regions

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

A long run of strong to extreme southwesterly wind continues into Monday, but change is under way. Wind slab and deep persistent slab natural activity is still possible. 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 noticed few large natural deep persistent slab avalanches in the alpine, we suspect these avalanches happened in the last 24- 48 hours and ran on basal facets. Intense wind transport in the alpine and tree line observed around the Icefields area.

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

Snowpack Summary

Recent strong to extreme southwesterly winds stripping exposed features and building wind slabs in the alpine and at tree line. In sheltered locations 30cm of low density snow lies over a generally weak mid and bottom snowpack with facets and depth hoar at the base. The height of snow is variable from 50 to 150cm.

Weather Summary

On Monday, winds will subside and precipitation will start in the afternoon. Up to 15 cm of snow forecast by Tuesday morning.On Tuesday, winds switch to light to moderate out of northeast, precipitation peters off by the morning and alpine temperatures will plummet to -25 C.

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.