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Avalanche Forecast

Archived

Feb 25th, 2023–Feb 26th, 2023

Alpine
Natural and human triggered avalanches likely.
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 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.

Regions

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

Saturday night's storm is expected to form touchy new storm slabs and dangerous avalanche conditions are expected on Sunday. Conservative terrain selection is essential and it is recommended to avoid avalanche terrain in heavy snowfall areas of the region.

Confidence

Low

Avalanche Summary

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, the new snowfall and strong southwest wind are expected to form touchy new slabs, especially in wind-loaded terrain.

Snowpack Summary

Stormy conditions return, bringing substantial snowfall and strong southwest wind Saturday night. This new snow will bury the interface from the recent period of cold Arctic air which includes reports of surface faceting, small surface hoar in sheltered areas, and widespread wind-affected surfaces and wind slabs in exposed terrain at higher elevations resulting from the recent northeast outflow 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 could wake up in isolated areas from the weight of the new storm 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 would be high. This layer is most likely to be human-triggered in thin, rocky slopes at alpine and upper treeline elevations.

Weather Summary

Saturday Night

Snowfall 15-35 cm, moderate to strong S-SW wind, treeline low around -18 °C.

Sunday

Snowfall 5-10 cm, light to moderate SW wind, treeline high around -12 °C.

Monday

Mainly cloudy with a chance of light flurries, light to moderate SW wind, treeline high around -12 °C.

Tuesday

Mainly cloudy with a chance of isolated flurries, light SE wind, treeline high around -9 °C.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Avoid all avalanche terrain during periods of heavy snowfall.
  • Use increased caution at all elevations. Storm snow is forming touchy slabs.
  • Closely monitor how the new snow is bonding to the old surface.
  • Storm slabs in motion may step down to deeper layers resulting in large avalanches.
  • 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.