Dashboard Regions Weather Stations Radar Alerts Glossary
Contact About
Log In

Register for an account and never miss a forecast again!

Register

Avalanche Forecast

Archived

Dec 12th, 2021–Dec 13th, 2021

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.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.

Regions

North Rockies.

Wind slabs are expected to be the primary concern on Monday. The wind is expected to switch directions so wind slabs should be expected on all aspects in exposed terrain. 

Confidence

Moderate - Uncertainty is due to the fact that deep persistent slabs are particularly difficult to forecast.

Weather Forecast

An Arctic ridge of high pressure brings cold and dry conditions to the region for the next few days.

Sunday Overnight: Partly cloudy with a chance of isolated flurries, light to moderate S winds, treeline temperature around -15 °C.

Monday: A mix of sun and cloud with a chance of isolated flurries, moderate to strong NE winds, treeline high around -15 °C. 

Tuesday: Mainly sunny, light to moderate NE winds, treeline high around -20 °C. 

Wednesday: Mainly sunny, light to moderate SW winds, treeline high around -16 °C. 

Avalanche Summary

On Saturday, a report on social media suggests there was an human triggered avalanche in the old Azu area outside Powder King but details on the avalanche are very limited. On Friday, the North Rockies field team reported shooting cracks and were triggering small slabs with ski cuts near treeline in the Pine Pass area. 

On Monday, wind slabs are expected to remain reactive to human triggering and natural wind slab avalanches are possible. The wind is expected to switch directions so wind slabs should be expected on all aspects. A lingering deep persistent problem still exists in the south of the region but appears to be gaining strength. This deep weakness is likely creating a low probability/high consequence scenario. 

Snowpack Summary

On Friday and Saturday, up to 20 cm of new snow was reported bringing the weekly storm snow accumulation to 40-70 cm. This new snow came in with strong winds from the southwest which formed highly reactive slabs in wind exposed terrain. On Monday, the wind is expected to switch directions and wind slabs should be expected on all aspects. Below the past week's storm snow, some surface hoar had been observed in sheltered areas at and below treeline but this appears to be isolated and has not been reactive in recent days. 

The lower snowpack consists of a series of early season crusts. Cold temperatures will have promoted faceting around these crusts. Shallow alpine slopes along the eastern side of the Rockies towards Jasper may have weaker, faceted snow near the ground. 

Snowpack depths at treeline range from 60cm-200cm, with the shallower value mainly on the eastern side of the range. The alpine snowpack ranges from 150cm-200cm. 

Terrain and Travel

  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Avalanche hazard may have improved, but be mindful that deep instabilities are still present.
  • Avoid shallow, rocky areas where the snowpack transitions from thick to thin.

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.