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Avalanche Forecast

Archived

Apr 4th, 2022–Apr 5th, 2022

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 possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely, human triggered possible.

Regions

Sea To Sky.

The recent storm snow is expected to be touchy on Tuesday and human-triggered avalanches are likely. 

Depending on the timing and amount of sun, solar-triggered avalanches are also possible. Extra caution is recommended around steep, sun-exposed slopes. 

Confidence

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

Weather Forecast

Unsettled conditions are expected for Tuesday as the storm system exits the region and a ridge of high pressure begins to build in its wake. 

Monday Night: Snowfall 10-25 cm, strong SW wind, freezing level low around 800 m. 

Tuesday: Cloudy in the morning with lingering flurries up to 5 cm, increasing sun in the afternoon, moderate to strong W wind easing through the day, freezing level high around 1300 m.

Wednesday: Mainly sunny, light to moderate SW wind, freezing level high around 1600 m.

Thursday: A mix of sun and cloud, light to moderate SW wind, freezing level high around 2500 m.

Avalanche Summary

Early reports from Monday include easily triggered soft slabs below treeline in the morning and explosive-triggered soft slabs up to size 2. 

On Sunday, several small skier triggered storm slabs were reported which were sliding on a melt-freeze crust as well as one isolated natural avalanche. One of these storm slabs was remotely triggered from 10 m away suggesting a weak bond between the storm snow and the underlying crust. Explosives triggered numerous small storm slabs and small cornice releases. 

On Saturday, explosive triggered a few cornices including a size 2 cornice which triggered a size 1 storm slab on the slope below. Ski cutting was triggering size 1 soft slabs with 5-15 cm of recent storm snow sliding on the firm melt-freeze crust. A skier also triggered a size 1 wind slab on a north aspect at 2100 m elevation which was 15 cm thick. This MIN report describes a small skier triggered wind slab which slid on a hard crust and a small natural avalanche which was solar triggered. 

Snowpack Summary

As of Monday afternoon, recent storm snow totals are estimated to be 70-100 cm. This storm snow has buried a strong, supportive crust which extends to mountain top on solar aspects and to around 2200 m on northerly aspects. Strong to extreme southwest wind has redistributed the new storm snow in exposed, high elevation terrain forming touchy wind slabs and developing large cornices. 

Below the crust, the upper snowpack consists of a number of crust/facet/surface hoar interfaces buried in March that seem to have bonded well during the recent warm weather. 

The middle and lower snowpack are generally strong and well bonded. 

Terrain and Travel

  • Continue to make conservative terrain choices while the storm snow settles and stabilizes.
  • Be aware of the potential for large avalanches due to the presence of a buried crust.
  • Avoid exposure to steep, sun exposed slopes, especially when the solar radiation is strong.
  • Pay attention to cornices and give them a wide berth when traveling on or below ridges.

Problems

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.