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Avalanche Forecast

Archived

Jan 2nd, 2021–Jan 3rd, 2021

Alpine
Natural and human triggered avalanches likely.
Treeline
Natural and human triggered avalanches likely.
Below Treeline
Natural and human triggered avalanches likely.
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

Lizard-Flathead.

A strong storm will impact the region over Saturday night through Sunday and an avalanche cycle is expected to occur. Travel in avalanche terrain is not recommended. 

Confidence

Moderate - Forecast snowfall amounts are uncertain.

Weather Forecast

SATURDAY NIGHT: Cloudy with snowfall bringing 15-20 cm of new snow. Strong southwest winds. Freezing level near 1500 metres.

SUNDAY: Cloudy with continuing snowfall bringing 10-15 cm of new snow, easing over the day with possible clearing in the afternoon. Moderate west winds. Alpine high temperatures around -4 with freezing levels near 1500 metres.

MONDAY: Partly cloudy with isolated flurries and a trace of new snow. Light southwest winds. Alpine high temperatures around -4.

TUESDAY: Cloudy with light flurries continuing from the overnight period and 10-15 cm of new snow, including overnight accumulations. Flurries easing over the day. Light southwest winds. Alpine high temperatures around -6.

Avalanche Summary

Saturday was a busy day for avalanches in the Fernie area, where explosives control yielded numerous storm slab releases reaching size 3 (very large). Two size 2.5 (large) natural storm slabs were also observed early in the morning in the same area. These occurred on bed surfaces of previous avalanches that had been reloaded by strong winds redistributing new snow.

Expect similar if not touchier conditions on Sunday as another powerful storm takes aim at the region and continues to build storm slabs with heavy snowfall and strong winds.

Snowpack Summary

Upwards of 30 cm of snow is forecast to accumulate in the region by Sunday afternoon. The snow will be accompanied by elevated freezing levels and strong southwest wind. Storm slabs are expected to build in sheltered terrain and wind slabs in exposed terrain at higher elevations.

In the Lizard Range, a melt-freeze crust has been reported around 20 to 40 cm deep and up to an elevation of 1900 m. A few reports suggest that sugary faceted grains may exist around the crust but others indicate no weakness. It remains to be seen if this layer will become an avalanche problem.

Around 50 to 100 cm deep, weak layers of feathery surface hoar and/or faceted grains may overly a hard melt-freeze crust. This layer appears to be bonding in certain areas of the region but remains suspect where it is well preserved.

Terrain and Travel

  • Watch for fresh storm slabs building throughout the day.
  • Approach lee and cross-loaded slopes with caution.
  • 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.

Persistent Slabs

Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.