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

Jan 1st, 2020–Jan 3rd, 2020

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

Regions

North Rockies.

A fine day Thursday before another storm rolls in on Friday. A weak layer lurks below the surface, so cautious terrain selection is required.

Confidence

Moderate - Uncertainty is due to the track & intensity of the incoming weather system.

Weather Forecast

Wednesday night: 4-8 cm new snow with strong westerly ridgetop winds. Freezing level lowering to valley bottom.

Thursday: Dry, with a mix of sun and cloud. Strong northwesterly winds. Treeline temperatures around -12°C.

Friday: 15-20 cm new snow with rain at lower elevations. Freezing level around 1600 m. Strong southerly winds.

Saturday: 10-15 cm new snow. Freezing level lowering to valley bottom. Strong southwesterly winds. 

Avalanche Summary

A wide, but relatively thin avalanche that involved a skier was reported from the Farm on December 29: https://avalanche.ca/mountain-information-network/submissions/a38b031a-7845-48fd-acdb-a0c00e9e2339. A similar event was reported from Pine Pass: https://avalanche.ca/map/forecasts/north-rockies?panel=mountain-information-network-submissions/4fc391f2-81cc-4725-a960-b2d71388ba70. These and several other avalanches reported Dec 29 to Dec 31 appear to have failed on a layer of surface hoar buried 30-40 cm below the surface.

Snowpack Summary

A weak layer of feathery surface hoar is buried around 40 cm below the surface. Avalanches have already been reported to have run on this layer and it is also showing "sudden" reactivity in snowpack tests. It is still at a burial depth where further storms will most likely increase, rather than decrease its reactivity.

There are a pair of weak layer in the middle of the snowpack. One is a surface hoar layer that appears to be gaining strength. The other is a layer of facets that lies above a relatively thin crust. Both these layers appear to be gaining strength.

The lower snowpack contains several crust layers, which could be a concern in shallow areas along the eastern slopes of the region.

Terrain and Travel

  • Choose conservative terrain and watch for clues of instability.
  • Be aware of the potential for larger than expected storm slabs due to the presence of buried surface hoar.
  • Avoid all avalanche terrain during periods of heavy loading from new snow and wind.

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.

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.