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

Feb 27th, 2019–Feb 28th, 2019

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

South Rockies.

Recently formed wind slabs and wind-affected snow may quickly be hidden under a thin cover of flurries falling through Thursday. Expect a more reactive snowpack in areas where winds pick up and 10 cm snowfall accumulates.

Confidence

Moderate - Wind effect is extremely variable

Weather Forecast

WEDNESDAY NIGHT: Clear with cloudy periods. Alpine temperatures near -12C. Ridgetop winds 10-15 km/h from the east.THURSDAY: Cloudy with scattered flurries, 5-10 cm. Alpine temperatures near -12C. Ridgetop winds 10-20 km/h from the southeast.FRIDAY: Mainly cloudy with isolated flurries, trace to 8 cm. Alpine temperatures near -19C. Ridgetop winds 15-25 km/h from the east.SATURDAY: Sunny with cloudy periods. Alpine temperatures near -22C. Ridgetop winds 10-15 km/h from the east.

Avalanche Summary

On Monday, small (size 1) wind slabs were reactive to skier traffic, and an isolated natural wind slab avalanche event up to size 2.5 likely occurred overnight Monday.Several large (size 2) wind slabs were triggered with explosives control in the Castle area on Friday after a bout of strong to extreme southwest winds. Slab depths ranged from 20-60 cm.A MIN report from Grizzly Peak in the Elkford area last Thursday describes a persistent slab failing on the mid-January persistent weak layer as a ski touring group ascended a steeper slope near treeline. See the report here.Also last Thursday in adjacent Waterton National Park, a recent large (size 2) deep persistent slab avalanche was observed. It occurred on a steep feature below treeline that was noted for its thin snowpack and for being reverse loaded by winds.

Snowpack Summary

Widespread wind affect has smoothed alpine terrain and loaded lee features. Harder wind slabs are found in more exposed terrain and higher elevations, softer wind slabs have formed in more sheltered areas.Below this stack of wind-affected snow, a weak layer of surface hoar or faceted grains buried mid-January is down 40 to 80 cm. It is found on shaded and sheltered slopes and is most prominent between 1600 m and 1900 m but has been found up to 2200 m. It may overly a melt-freeze crust on south aspects. Recent avalanche reports and snowpack test results suggest that this layer remains reactive to human triggers.The bottom half of the snowpack is composed of weak and sugary faceted snow crystals.

Problems

Wind Slabs

Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind 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.