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Avalanche Forecast

Archived

Mar 15th, 2024–Mar 16th, 2024

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

Regions

Purcells, Dogtooth, East Purcell.

Avoid being in or under avalanche terrain.

Intense spring sun and rising temperatures have increased the risk of large natural and rider-triggered avalanches.

Confidence

High

Avalanche Summary

Thursday, several loose wet avalanches, a large (size 2.5) naturally triggered persistent slab and a skier-triggered avalanche were observed. (See photos)

Wednesday, west of Golden, a large, human-triggered persistent slab avalanche was reported. This avalanche was triggered on a ridge crest that had been previously ski-cut.

Looking forward, we are expecting persistent avalanche problems to become worse with rising temperatures and intense spring sun.

Snowpack Summary

During the day, frozen and crusty surface snow will melt and turn moist or slushy due to high freezing levels combined with intense sun. This will be especially prevalent on sunny slopes and at lower elevations. This will cause the avalanche hazard to rise as the day warms. High-elevation shady north-facing slopes may still have some dry snow.

A widespread crust is buried roughly 80-120 cm deep. Weak faceted crystals and surface hoar above this crust are contributing to large avalanches across the province and continue to be the primary layer of concern here.

The basal snowpack is generally weak and faceted, with the potential to produce very large avalanches with the forecast of prolonged warming.

Weather Summary

Friday Night

Mostly clear. No new snow expected. 15 km/h northwest ridgetop wind. Treeline temperature around 0 °C. Freezing level around 2900 m with a potential temperature inversion below 1800 m.

Saturday

Sunny. No new snow expected. 10 km/h northwest ridgetop wind. Treeline high around 7 °C. Freezing level around 3000 m with a overnight temperature inversion below 1800 m.

Sunday

Sunny. No new snow expected. 5 km/h variable ridgetop wind. Treeline high around 8 °C. Freezing level rising to 3200 m.

Monday

Mostly sunny. No new snow expected. 5 km/h east ridgetop wind. Treeline high around 8 °C. Freezing level rising to 3300 m.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Only the most simple non-avalanche terrain free of overhead hazard is appropriate at this time.
  • Be aware of the potential for large, deep avalanches to run full path or even longer.
  • The likelihood of deep persistent slab avalanches will increase with each day of warm weather.
  • As surface loses cohesion due to melting, loose wet avalanches become common in steeper terrain.

Problems

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.

Loose Wet

Loose Wet avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.

Deep Persistent Slabs

Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.