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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

South Coast Inland.

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

Low - Uncertainty is due to the timing or intensity of solar radiation and its effect on the snowpack. Uncertainty is due to the limited number of field observations.

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 5-15 cm, strong SW wind, freezing level low around 1000 m. 

Tuesday: Mainly cloudy with lingering flurries in the morning and sunny breaks in the afternoon, moderate to strong W wind, freezing level high around 1400 m.

Wednesday: Mainly sunny, light to moderate SW wind, freezing level high around 1800 m.

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

Avalanche Summary

On Sunday, ski cutting in the north of the region triggered several storm slabs on north and east aspects at 2000-2100 m elevation which were typically 30 cm thick and sliding on a melt-freeze crust. Visibility was limited but natural avalanches up to size 2 were also suspected. This MIN report describes triggering a couple small storm slabs and observations of shooting cracks. In the Coquihalla, a few small natural glide slab avalanches were reported from the smooth rock slab features as well as a few small wet loose avalanches from steep slopes. 

On Saturday in the north of the region, a skier triggered a size 1 wind slab on a northeast aspect at 2450 m which had an average thickness of 25 cm and slid on a melt-freeze crust. In the Coquihalla area, this MIN report and this MIN report describe small skier-triggered soft slab avalanches which were 5-20 cm thick. This MIN report describes wind loading and shooting cracks in the recent 10-15 cm of storm snow. 

Snowpack Summary

As of Monday afternoon, recent storm snow totals are estimated to be 30-60 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 southwest wind has redistributed the new storm snow in exposed, high elevation terrain forming touchy wind slabs and developing large cornices. 

The rest of 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.
  • Pay attention to cornices and give them a wide berth when traveling on or below ridges.
  • Cornices become weak with daytime heating or solar exposure.

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.