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 19th, 2019–Dec 20th, 2019

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

Regions

South Rockies.

New snow (and maybe rain at lower elevations), gusty winds, and rising temperatures are priming the snowpack for a natural avalanche cycle. Hazard will rise through Friday, peaking later in the day.

Confidence

Moderate - Uncertainty is due to the track & intensity of the incoming weather system. We are confident the likelihood of avalanche will increase with the arrival of the forecast weather.

Weather Forecast

Thursday Night: Snow and flurries, 5-15 cm. Alpine temperature -8 C. Southwest wind 20-35 gusting to 60 km/hr.

Friday: Snow, heavy at times 20-30 cm. Alpine temperature -3 C. Southwest wind 20-40 gusting to 65 km/hr. Freezing level rising to 1600 m.

Saturday: Continued snowfall, 15-30 cm. Alpine temperature -2 C. Southwest wind 50 gusting to 80 km/hr. Freezing level 1600 m.

Sunday: Flurries, up to 10 cm. Alpine temperature -5 C. West wind 20-30 gusting to 50 km/hr. Freezing level dropping to valley bottom.

Avalanche Summary

Explosives triggered 2 small (size 1) wind slabs on Wednesday. A few small (size 1) natural avalanches were noted around the Castle area on Tuesday and skiers reported fresh wind slabs cracking underfoot.

Snowpack Summary

Wind has scoured exposed terrain and formed wind slabs in the alpine, and around lee features and lower into start zones. Forecasted snowfall will cover a variable and wind-affected surface and is expected to build and develop reactive storm slabs.

The bottom half of the snowpack consists of crusts from November and October and basal facets. These persistent weak layers produced large avalanches over a week ago but have since gained strength. Overall, a shallow and variable snowpack is found around the region. Snowpack depths range between 50-100 cm around treeline and taper rapidly below.

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.