Avalanche Forecast

Archived

Mar 3rd, 2021–Mar 5th, 2021

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Below Threshold.

Alpine

Natural avalanches unlikely, human triggered possible.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Below Threshold.

Alpine

Natural avalanches unlikely, human triggered possible.

Treeline

Natural avalanches unlikely.

Below Treeline

Below Threshold.

Regions

Yukon.

Be in initial assessment mode once the highway to White Pass reopens. Natural avalanche activity there has been extensive. If you're diverted to Wheaton Valley for another day, be mindful of its generally weaker snowpack structure and choose terrain accordingly.

Confidence

Moderate - Uncertainty is due to the limited number of field observations.

Weather Forecast

WEDNESDAY NIGHT: Cloudy with scattered flurries bringing about 5 cm of new snow. Light to moderate southeast winds.

THURSDAY: Cloudy with isolated flurries and a trace of new snow. Light variable winds. Alpine high temperatures around -11.

FRIDAY: A mix of sun and cloud. Moderate southwest winds. Alpine high temperatures around -12.

SATURDAY: A mix of sun and cloud. Light south winds. Alpine high temperatures around -11.

Avalanche Summary

Observations from the recent stormy period are still limited, due in part to a closure on the South Klondike Highway.

We have a report from the highways team that describes a widespread natural avalanche cycle on all west, south, and east aspects. Many avalanches ran full path, affecting the road in places not normally observed.

Since recreational traffic has been diverted elsewhere in the region, we have recent social media and MIN reports from the Wheaton Valley, like this one from Tuesday and another from Tally Ho on Monday that give a good idea of a reactive upper snowpack anywhere wind has been able to reach, even quite low elevations.

The description of 'Wheatonesque whumpfs' is a great clue to remind users that this area is very different from White Pass and usually hosts a much thinner, weaker snowpack structure than the Pass.

Snowpack Summary

4-day snowfall totals in the region are estimated to be around 50 cm. Strong to extreme southwest winds throughout the stormy period have been redistributing this snow into thicker, reactive wind slabs in leeward and crossloaded terrain features.

An estimated 100 or more cm of accumulated snow may now overlie a layer of surface hoar in sheltered areas, previously reported here and here. Given its new depth and the lack of recent avalanche activity attributed to it, this layer may prove to be a transient weakness that has since been overshadowed by new wind slab development.

The lower snowpack is strong around White Pass, but inland areas like the Wheaton Valley very likely have a thinner and weaker structure. This is especially notable while the South Klondike highway closure continues to divert users to inland areas.

Terrain and Travel

Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
Watch for areas of hard wind slab on alpine features.
Seek out sheltered terrain where new snow hasn't been wind-affected.

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.