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Avalanche Forecast

Archived

Dec 25th, 2019–Dec 26th, 2019

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 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

Cariboos.

Natural avalanche activity has waned, but a persistent slab 40 to 100 cm in depth remains very much in play. You can't feel a problem like this under your track or skis, the only way to manage this is to stick to relatively simple terrain free of overhead hazard.

Confidence

Moderate - Uncertainty is due to the fact that persistent slabs are particularly difficult to forecast.

Weather Forecast

The most recent weather model runs are showing very little precipitation through the end of the year aside from small dribs and drabs. Looks like the wind will begin to pick up out of the south/southwest on Thursday.

WEDNESDAY NIGHT: Freezing level at valley bottom, light northwest wind, no significant precipitation expected.

BOXING DAY: Clear skies at dawn with increasing cloud cover throughout the day, overcast by sundown. Freezing level at valley bottom, moderate to strong south/southwest wind, trace of snow possible during the day, potential for 2 to 6 cm by Friday morning.

FRIDAY: Broken cloud cover, freezing level at valley bottom, moderate to strong west/southwest wind, trace of snow possible during the day.

SATURDAY: Scattered cloud cover at dawn building to overcast by sundown, freezing level at valley bottom, strong southerly wind, no precipitation expected.

Avalanche Summary

There is a notable weak layer of surface hoar that is down 40-100 cm and human triggering remains possible. Treat this layer with caution and choose relatively conservative terrain.

No new activity was reported on Monday or Tuesday.

On Sunday, there were reports of numerous natural and explosives triggered avalanches up to size 2.5

On Saturday, there were a few reports of natural and human triggered avalanches up to size 2. Check out this MIN report detailing the touchy conditions found in the Allan Creek area on Saturday.

On Friday, there were a few reports of natural and human triggered avalanches. Check out this great MIN report from Allan Creek that outlines reactive storm slab conditions. Here is another great MIN report about similar conditions further north in the region.

Snowpack Summary

The Cariboos have seen up to 70 cm of new snow over the past week.

40-100 cm of snow is now sitting on a widespread layer of feathery surface hoar crystals. There is some uncertainty as to how much strength this interface has gained over the last few days and it should be treated with caution.

A weak layer formed in late November is now buried around 1 m or more below the surface. This interface may present as surface hoar, a crust, facets or a combination, depending on elevation and aspect.

Terrain and Travel

  • Use conservative route selection. Choose simple, low-angle, well-supported terrain with no overhead hazard.
  • Shooting cracks, whumphs and recent avalanches are strong indicators of an unstable snowpack.
  • Caution around convexities or sharp changes in terrain.
  • Fresh wind slabs will likely form throughout the day, diligently watch for changing conditions.
  • Avalanche hazard may have improved, but be mindful that deep instabilities are still present.

Problems

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.

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.