Avalanche Forecast

Archived

May 1st, 2021–May 3rd, 2021

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.

Alpine

Natural avalanches unlikely, human triggered possible.

Treeline

Natural avalanches unlikely.

Below Treeline

Below Threshold.

Regions

Yukon.

Avalanche conditions likely vary with elevation. Wind slabs may linger in the alpine and loose wet activity is possible at lower elevations.

Confidence

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

Weather Forecast

SATURDAY NIGHT: alpine -4C, wind south 10 km/hr, mostly cloudy, trace precipitation

SUNDAY: alpine low -5C high -2C, wind south 15 km/h, mix of sun and cloud, trace precipitation

MONDAY: alpine low -3C high -1C, wind southeast 15 km/h, mostly cloudy, light precipitation, 1 to 3 cm accumulation

TUESDAY: alpine low -3C high -1C, wind south 30 km/h, mostly cloudy, light precipition, 2 to 5 cm accumulation

Avalanche Summary

Large (size 2) wet loose avalanches have been observed throughout the region, particularly during periods of rain or with warm air temperature.

Snowpack Summary

Above 1400 m, around 20 cm of dry snow may be found, which overlies a hard melt-freeze crust or other hard surfaces. Below 1400 m, the upper snowpack is wet from recent rain and warm air. The snowpack is isothermal near highway elevations, meaning it is generally unsupportive to human traffic.

The lower snowpack in White Pass is deep for this time of year with no layers of concern. Areas further inland, such as the Wheaton Valley, may have a shallower and weaker snowpack.

Cornices are still very large. Recent cold temperatures have kept cornice failures to a minimum but they should always be treated with respect in the spring, especially when the air temperature rises.

Terrain and Travel

Carefully evaluate steep lines for wind slabs.
Pay attention to cornices and give them a wide berth when traveling on or below ridges.
A moist or wet snow surface, pinwheeling and natural avalanches are all indicators of a weakening snowpack.
Avoid terrain traps where the consequence of any avalanche could be serious.

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.

Cornices

Cornice Fall is the release of an overhanging mass of snow that forms as the wind moves snow over a sharp terrain feature, such as a ridge, and deposits snow on the downwind (leeward) side. Cornices range in size from small wind drifts of soft snow to large overhangs of hard snow that are 30 feet (10 meters) or taller. They can break off the terrain suddenly and pull back onto the ridge top and catch people by surprise even on the flat ground above the slope. Even small cornices can have enough mass to be destructive and deadly. Cornice Fall can entrain loose surface snow or trigger slab avalanches.

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.