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 5th, 2019–Dec 6th, 2019

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

Regions

North Columbia.

Avalanche danger will be highest late in the day as new snow accumulates.

Confidence

Moderate - Uncertainty is due to the timing of the incoming weather system.

Weather Forecast

Thursday night: Scattered flurries, 5-10 cm. Alpine temperature -5 C, southwest wind 25-40 km/hr.

Friday: Snow, 10-20 cm. Alpine temperature -3 C, southwest wind 25-35 km/hr.

Saturday: More snow, 10-20 cm. Alpine temperature -4, southwest wind 20-30, gusting to 45 km/hr.

Sunday: Sunny with cloudy periods. Alpine temperature -10 C, north wind 10-20 km/h.

Avalanche Summary

On Wednesday, storm snow continued to be reactive to skier traffic, including triggering slab avalanches to size 2 and cracking on small, supported slopes. A couple of field observations reported slab avalanches failing on a layer of surface hoar (down 60-80 cm) at treeline elevations.

On Tuesday, a natural avalanche cycle was observed in Glacier National Park. Numerous size 2 storm slab avalanches were observed on all aspects at 2200 m and above. Additionally, 2 size 3 storm slab avalanches were observed on a north aspect at 2165 m and a northwest aspect at 2400 m. Near Revelstoke, storm slab avalanches to size 2 were reacting easily to explosives, many occurring on north and northeast aspects from 1800-2300 m.

Snowpack Summary

Storm snow totals reached 30-50 cm early this week along with moderate westerly winds. Slabs have formed in areas exposed to wind. 

The storm snow covered a faceted upper snowpack and previously wind-affected surfaces, and surface hoar in sheltered areas around treeline and below.

Down 40-80 cm, a layer of surface hoar (feathery crystals) may be found in sheltered areas around treeline. In these areas old, stubborn wind slabs may still be reactive where they overly the weak surface hoar on a crust.

A variety of crusts from late October are buried deeper in the snowpack. Total snow depths range from 100-170 cm around tree line.

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.