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Avalanche Forecast

Archived

Mar 18th, 2023–Mar 19th, 2023

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

Regions

South Coast Inland, Birkenhead, Duffey, South Chilcotin, Stein, Taseko.

The March sun packs a punch and can quickly destabilize the snowpack. Be suspect of sunny slopes or overhead hazards like cornices during the heat of the day.

Confidence

Moderate

Avalanche Summary

On Wednesday, dry loose natural avalanches were seen from steep terrain up to size 1.5. A skier-controlled size 1 wind slab and several natural cornice failures up to size 2 were also reported. There are limited observations from the far northern end of the forecast region, however, a reactive layer of surface hoar buried under the recent storm snow was reported near the Homathko Icefield. On Wednesday, skiers found a reactive layer of surface hoar buried 65 cm deep below the recent storm snow, and observed natural avalanches to size 3.

On Tuesday, several skier-controlled slab avalanches (size 1.5) were reported on wind-loaded features at treeline and above. Dry loose sluffing was noted from steep northeast terrain up to size 1.5.

On Monday, several natural cornice falls were reported in the northern part of the region up to size 2.5.

On Sunday, a natural large size three, wind slab avalanche was observed. It started in a cross-loaded feature in the alpine and it may have stepped down to weaker buried layers.

Snowpack Summary

Daytime warming and solar radiation will promote moist snow surfaces, destabilizing the upper snowpack on all aspects upwards of 1500 m and higher on solar slopes. Cornices loom over ridgelines and may become weak during periods of solar radiation and warming.

A sun crust has formed on solar aspects. On more northerly and sheltered slopes at upper tree line and higher, 20-40 cm recent snow covers an older sun crust on steep solar aspects, and older faceted snow in sheltered areas. Recent southwest wind pressed surfaces and formed slabs on lee slopes at exposed treeline and into the alpine.

The mid-snowpack is well consolidated. There is a widespread weak layer of large sugary facets at the bottom of the snowpack. Recent avalanche activity on this layer has been confined to northern parts of the region in the Chilcotins. This layer remains a concern in shallow snowpack areas.

Weather Summary

Saturday night

Starry sky with increasing clouds. South wind 5-15 km/hr. Treeline low temperature -9 C. Freezing level dropping below 1100 m.

Sunday

Mix of sun and cloud. Southeast wind 10-20 km/hr. Treeline high temperature +3 C, freezing level spiking around 1800 m.

Monday

Increasing cloudiness, and possible light flurries late in the day. East wind 10-20 km/hr. Treeline high temperature +1 C. Freezing level 1500 m.

Tuesday

Sunny and clearing skies. Light northeast wind. Treeline high temperature +2 C. Freezing level 1600 m.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Be careful with wind slabs, especially in steep, unsupported and/or convex terrain features.
  • Avoid sun exposed slopes when the solar radiation is strong, especially if snow is moist or wet
  • Pay attention to cornices and give them a wide berth when traveling on or below ridges.
  • In areas where deep persistent slabs may exist, avoid shallow or variable depth snowpacks and unsupported terrain features.

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.

Deep Persistent Slabs

Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.