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Avalanche Forecast

Archived

Mar 29th, 2024–Mar 30th, 2024

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

Regions

Purcells, Dogtooth, East Purcell, West Purcell.

10 to 20 cm of recent snow and southwest wind have formed wind slabs reactive to human triggers in specific locations below ridgecrests.

Confidence

Moderate

Avalanche Summary

On Thursday, several natural and rider triggered wind slab avalanches up to size 1.5 were reported on mostly northerly aspects at treeline and above.

A few naturally triggered wet loose avalanches up to size 2.5 were reported on steep, sunny slopes in the alpine.

Snowpack Summary

10 to 20 cm of recent snow overlies a crust on all but north facing aspects at treeline and above where a weak layer of surface hoar may be present.

A widespread crust with facets above is buried 40 to 110 cm deep. Steep or convex terrain features with a shallow or thin to thick snowpack at treeline and above are the most likely places to trigger this layer.

Weak facets at the base of the snowpack remain a concern in steep, rocky alpine terrain with a shallow or thin to thick snowpack.

Weather Summary

Friday Night

Mostly cloudy with isolated flurries, 0 to 5 cm snow. 10 to 20 km/h northwest ridgetop wind. Treeline temperature -8° C. Freezing level valley bottom.

Saturday

Sunny. 10 to 20 km/h west ridgetop wind. Treeline temperature -3° C. Freezing level 1700 m.

Sunday

Mostly sunny. 10 to 20 km/h north ridgetop wind. Treeline temperature -2° C. Freezing level 1800 m.

Monday

Sunny. 10 to 20 km/h northwest ridgetop wind. Treeline temperature 3° C. Freezing level 2500 m.

Check out the Mountain Weather Forecast for additional weather information.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Avoid steep, rocky, and wind effected areas where triggering slabs is more likely.
  • If triggered loose wet avalanches may step down to deeper layers resulting in larger avalanches.
  • When a thick, melt-freeze surface crust is present, avalanche activity is unlikely.
  • Cornice failure may trigger large avalanches.

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.

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.