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 28th, 2021–Dec 29th, 2021

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

Regions

Kootenay Boundary.

Recently formed storm slabs will be most reactive to human triggers in wind affected terrain.

A persistent slab problem has created a low likelihood, high consequence scenario that is best avoided through conservative terrain choices.

Confidence

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

Weather Forecast

TUESDAY NIGHT: Partly cloudy / Light north wind / Low of -24

WEDNESDAY: Sunny / Light north wind increasing to moderate in the afternoon / High of -17

THURSDAY: Mix of sun and cloud / Light to moderate northwest wind / High of -17

FRIDAY: Sunny / Light northeast wind / High of -17

Avalanche Summary

A rider triggered size 2.5 persistent slab avalanche involving several riders was reported near Nelson on Monday. The avalanche occurred on a southeast aspect at approximately 1900 m. It failed on the crust formed in early December. The treeline slope was heavily wind effected and the rider triggered the avalanche from a thin spot where the layer was only around 60 cm deep. There is a MIN report of the incident.

Additionally, several natural and human triggered storm slab avalanches up to size 2.5 were reported on all aspects and elevations on Monday. An example of a skier triggered storm slab near Rossland can be found in a MIN report HERE.

Snowpack Summary

Recent storm totals reached over 100 cm. Expect dry loose avalanches (sluffing) running far and fast in steep terrain. There is a lot of snow available for transport which will form fresh wind slabs when wind speeds increase to moderate.

The recent snow reportedly covered a thin freezing rain crust and a surface hoar interface, which has been responsible for recent storm slab avalanches. For now, we don't expect the new snow to bond well to the old interface. 

A crust from early December is now 50-120 cm below the surface, and is found up to 2300 m. A layer of weak facets (sugary snow) has been reported above and below this crust, and is the layer of concern in our persistent avalanche problem.

The lower snowpack is composed of several early-season crusts. Snow depths at treeline average 150-300 cm.

Terrain and Travel

  • Use small low consequence slopes to test the bond of the new snow.
  • Pay attention to the wind, once it starts to blow fresh sensitive wind slabs are likely to form.
  • Seek out wind sheltered terrain below treeline where you can avoid wind slabs and find great riding.
  • Be aware of the potential for large avalanches due to the presence of a persistent slab.
  • Avoid shallow, rocky areas where the snowpack transitions from thick to thin.

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.