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Avalanche Forecast

Archived

Feb 26th, 2023–Feb 27th, 2023

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 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.

Regions

Cariboos, Blue River, Clearwater, McBride, Premier, Quesnel, Sugarbowl, Clemina, North Monashee, Renshaw, Robson.

Don't be too quick to rule out the storm slab problem on Monday. That heap of new snow sits on a questionable interface in many areas. Use low consequence slopes to assess the new snow's bond and raise your guard as you approach exposed terrain where new wind slabs pose a more certain hazard.

Confidence

Moderate

Avalanche Summary

Observations of new avalanche activity from Saturday and Sunday aren't in yet but we anticipate some degree of a natural avalanche cycle took place throughout the region but especially where 30 cm or more new snow accumulated on Saturday.

Many small to large (size 1 to 2.5) wind slabs were triggered naturally and by riders over the past few days. They mostly occurred on south to west aspects at alpine elevations resulting from northeasterly outflow winds. A few very large (size 3.5 to 4) deep persistent slab avalanches were also observed over the week, which likely occurred during very windy conditions.

Looking forward, we expect widespread surface instabilities to become more focused toward wind loaded areas.

Snowpack Summary

Stormy conditions brought up to about 30 cm of new snow to the region along with strong southwest wind on Saturday. The Mica Mountain area may have as much as 50 cm! The new snow buried an interface which includes reports of faceted (sugary) surface snow, small surface hoar in sheltered areas, and more widespread heavy wind effect and wind slabs at higher elevations from recent northeast winds.

Prior to the storm, a small layer of surface hoar crystals could be found about 50 to 100 cm deep, particularly in areas sheltered from the wind around treeline. This layer appears to be gaining strength and is currently considered dormant, but may have woken up in isolated areas from the weight of the new snow.

Large and weak facets that formed in November are found near the base of the snowpack. Although the likelihood of triggering this layer is low at this time, the consequence of doing so remains very high. This layer is most likely to be human-triggered in thin, rocky slopes at alpine and upper treeline elevations.

Weather Summary

Sunday night

Easing flurries bringing less than 5 cm of new snow. Light southwest winds.

Monday

Mainly cloudy with isolated flurries. Light south winds. Treeline high temperatures around -10 °C.

Tuesday

Mainly cloudy with isolated flurries. Light variable winds. Treeline high temperatures around -9 °C.

Wednesday

Cloudy with isolated flurries, increasing overnight. Winds increasing to Moderate southwest by end of day. Treeline high temperatures around -10.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Carefully assess open slopes and convex rolls where buried surface hoar may be preserved.
  • Avoid shallow, rocky areas where the snowpack transitions from thick to thin.

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.

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.