Avalanche Forecast

Archived

May 4th, 2023–May 5th, 2023

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches possible, human triggered probable.

Below Treeline

Natural avalanches possible, human triggered probable.

Alpine

Natural avalanches unlikely, human triggered possible.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Alpine

Below Threshold.

Treeline

Below Threshold.

Below Treeline

Below Threshold.

Regions

Glacier.

Natural avalanches are still possible, limit time in avalanche path runouts on all aspects.

With no overnight refreeze for a week, the upper snowpack is very soft, making for difficult travel and hazardous riding conditions.

Confidence

High

Avalanche Summary

Avalanche control today has produced isolated sz 4 and numerous sz 2-3 avalanches. This is capping off a very active week of spring avalanche activity. Which had wet/loose natural and controlled avalanches with numerous sz 3, and isolated sz 4's. Many avalanche paths failed down to ground once the avalanches reached Treeline elevations and lower.

Snowpack Summary

Warm temps have penetrated the snowpack creating an moist, isothermal snowpack treeline and below on all aspects and into the alpine on solar aspects. Buried crusts in the upper 50 cm are breaking down. Shallow snowpack features have loose, weak snow to ground.

20-40cm above the ground the Nov 17 basal weakness can still be found in many areas.

Weather Summary

Warm and dry weather will come to an end on Fri, as a trough of low pressure brings light precip and dropping freezing levels.

Tonight: Clear, Alpine Low 8°C, FZL 3200m, mod E ridgetop wind

Fri: Sunny w/cloudy periods, Alp High 12°C, FZL 3500m, mod, gusting to strong E winds

Sat: Cloudy w/sunny periods + iso wet flurries, Alp high 6°C, FZL 2800m, mod S winds

Terrain and Travel Advice

Minimize exposure to overhead avalanche terrain, large avalanches may reach the end of runout zones.
As surface loses cohesion due to melting, loose wet avalanches become common in steeper terrain.
If triggered loose wet avalanches may step down to deeper layers resulting in larger avalanches.

Problems

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.