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Avalanche Forecast

Archived

Apr 6th, 2022–Apr 7th, 2022

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

Regions

South Columbia.

Recent storm snow combined with significant warming and solar radiation are driving the avalanche hazard, especially by the afternoon.

Check out the Forecaster Blog for additional details.

Confidence

Moderate - Uncertainty is due to the timing or intensity of solar radiation and its effect on the snowpack.

Weather Forecast

Thursday: A mix of sun, clouds, and very WARM. Freezing levels rise to 3000 m by the afternoon. Alpine temperatures +5C and ridgetop wind moderate to strong from the southwest. 

Friday: No overnight refreeze and WARM. The freezing level holds at 3000 m but should start to drop by 4 pm. Cloudy with a mix of rain and snow up to 15 mm. Ridgetop winds strong from the southwest.

Saturday: Cloudy and cold with new snow up to 10 cm. Freezing levels drop to 1000 m and ridgetop winds switch to the northwest. 

Avalanche Summary

On Tuesday, a natural avalanche cycle was noted up to size 2, mostly storm slabs and one persistent slab. A couple of skier remotely (from a distance away) triggered slabs were seen up to size 1.5 and dry loose avalanches up to size 1.5. 

On Monday, evidence of a widespread natural avalanche cycle up to size 3 but the average storm/ wind slabs were reported to size 2 and failed in the recent storm snow. Some larger avalanches may have failed on the end of March melt-freeze crust. Most notable was a natural size 3.5 storm slab that started at 2600 m and ran to the valley bottom. 

Warm temperatures and solar radiation will likely trigger a natural avalanche cycle on Thursday and Friday

Snowpack Summary

By the afternoon on Thursday, wet snow surfaces may exist to mountain top on most aspects leaving only high North facing terrain with some dry snow. 

15 to 30 cm of storm snow has blanketed the region and buried multiple crusts in the upper snowpack. Moderate to strong west/ southwest wind has redistributed some of the new storm snow in exposed high elevation terrain forming wind slabs and developing large cornices.

The new snow brings 60-80 cm above will a crust from late March. This crust is present on all aspects up to an elevation of 2600 m. 

The early-December rain crust is approximately a metre off the ground. Large slab avalanches failed on this interface last week following a rain and warming event. This layer may be active over the next two days of warm weathern. 

Terrain and Travel

  • Avoid all avalanche terrain during periods of intense solar radiation.
  • Be aware of the potential for large avalanches due to the presence of a persistent slab.
  • Cornices become weak with daytime heating or solar exposure.
  • Minimize overhead exposure; avalanches triggered by warming or cornice fall may be large and destructive.

Problems

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.

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.