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 1st, 2020–Dec 2nd, 2020

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

Regions

South Coast Inland.

The snowpack doesn't respond well to rapid change. The impact of the afternoon sun and warm temperatures could bump up the avalanche danger to HIGH. Watch for signs of instability and be conservative with your terrain selection.

Confidence

Moderate - Uncertainty is due to the timing or intensity of solar radiation and its effect on the snowpack.

Weather Forecast

Wednesday: Sunny with some cloudy periods. Ridgetop winds 15-25/h km from the south and alpine temperatures + 8 degrees. Freezing levels 3500 m.

Thursday: A mix of sun and cloud. Ridgetop winds 10-20 km/hr from the southwest and alpine temperatures near + 4 degrees. Freezing levels 3000 m.

Friday: A mix of sun and cloud. Ridgetop winds 15-30 km/hr from the southwest and alpine temperatures + 5 degrees. Freezing levels 3000 m.

Avalanche Summary

On Tuesday, a large size 3 natural avalanche was observed on a NE aspect at 2400 m. It was reported as a cornice failure triggering the slope below and appeared to have slid on the early November crust near the base of the snowpack.

On Wednesday, we may see more of these deeper releases with the warm up as well as smaller natural avalanches becoming especially reactive where recent snow sits over a crust or surface hoar. Loose wet avalanches are also likely. 

Our eyes and ears in the mountains are limited at this time of year and may continue this winter due to fewer professional observations. If you see anything (or don't) while out in the field, please consider sharing via the Mountain Information Network (MIN). Photos are especially helpful! Thank you so much for all the great MINs submitted so far!

Snowpack Summary

10-20 cm of recent snow has been wind loaded into lee features in exposed areas at upper elevations and may sit over a thin melt-freeze crust on south aspects and possibly surface hoar in wind-sheltered areas around treeline. Forecast sun and rising freezing levels into the alpine will have the greatest impact on the upper snowpack, showing signs of instability.

The lower snowpack is characterized by a few crusts formed during warm periods over the last month. 

  • In the north, treeline snowpack depth sits around 80 to 120 cm. The crust of note here is sitting near the base of the snowpack, likely surrounded by a weak layer of sugary facets. Snowpack tests and recent avalanche activity suggest that this layer could be triggered by humans and produce large avalanches.

  • In the south of the region, the snow line has been reported around 700 m near Hope and treeline snowpack depth sits around 100-150 cm. The deeper crusts in this area are generally well bonded to surrounding snow.

Terrain and Travel

  • The likelihood of deep persistent slab avalanches will increase with each day of warm weather.
  • Avoid slopes when the solar radiation is strong, especially if they have large cornices overhead.
  • Avoid steep slopes when air temperatures are warm, or solar radiation is strong.

Problems

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.

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.