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Avalanche Forecast

Archived

Apr 30th, 2021–May 1st, 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, human triggered possible.
Below Treeline
Below Threshold.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely.
Below Treeline
Below Threshold.

Regions

Yukon.

We've had rain at Fraser and freezing levels have been difficult to track in White Pass over the last 24hrs. Rain likely turns to snow at upper elevations and reactive Wind Slabs could be present in the high alpine.

Confidence

Moderate - Uncertainty is due to difficult to forecast freezing levels.

Weather Forecast

FRIDAY NIGHT: -2C, wind S/SW 20km/hr, cloudy, 3cm of sleet at valley bottom, 5cm snow in the Alpine. Freezing level 1500m

SATURDAY: low -2C high 2C, wind S/SW 10km/hr, broken skies, light precipitation ending around noon

SUNDAY: low -2C high 3C, wind variable 10km/hr, broken skies, trace precipitation

MONDAY: low -6C high 4C, wind N/NE 10km/hr, scattered clouds

Avalanche Summary

Wet snow now overlies firm surfaces. In some places, this wet snow is not sticking well. Check out this MIN for more details. 

Wet loose avalanches up to size 2 have been observed throughout the region.

These types of avalanches will continue until we once again see below freezing temperatures overnight.

A big THANK YOU to all of you that provided us and fellow recreationists with observations this season. Please continue to do so if you head out!

Snowpack Summary

White Pass has now received over 24hrs of light rain and sleet at highway elevations. This has been accompanied by high freezing levels. This has contributed to the snowpack at lower elevations trending to isothermal and unsupportive. Above 1500m, the snowpack remains supportive to travel and dryer snow likely exists. 

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 temperatures rise.

Terrain and Travel

  • A moist or wet snow surface, pinwheeling and natural avalanches are all indicators of a weakening snowpack.
  • Keep in mind that wet avalanches can be destructive due to their high density.
  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Minimize your exposure time below cornices.
  • Pay attention to cornices and give them a wide berth when traveling on or below ridges.

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.

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.