Dashboard Regions Weather Stations Radar Alerts Glossary
Contact About
Log In

Register for an account and never miss a forecast again!

Register

Avalanche Forecast

Archived

Jan 5th, 2012–Jan 6th, 2012

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 and human triggered avalanches likely.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches possible, human triggered probable.

Regions

Cariboos.

Confidence

Fair - Forecast snowfall amounts are uncertain on Sunday

Weather Forecast

Expect freezing levels to drop back to valley bottoms by Friday morning as a weak ridge of high pressure moves in from the coast. High clouds may become broken skies by afternoon, providing a bit of sunshine to some of the more western areas. Friday night is forecast to be cooler again, with mountain top temperatures dipping to at least -15.0 C. The ridge should continue to affect the interior mountains on Saturday resulting in mostly clear skies and ridgetop highs around -8.0 C. The next Pacific system is on track to bring warm windy and wet weather for Sunday. Preliminary models show freezing levels rising to about 1400 metres combined with about 20 cm of new snow.

Avalanche Summary

There have been a few reports of natural cornice falls landing on slopes and entraining enough snow to get to size 2.5. The interesting thing here is that these cornice falls did not propagate wide releases on buried persistent weak layers. These slopes may have already released from natural or human triggers. I suspect that there was a natural avalanche cycle Wednesday night or early Thursday morning that has not been reported due to poor visibility and travel conditions.

Snowpack Summary

The height of snow in the region is between 200 cm in the drier areas and close to 300 cm in the wetter areas. There was another 10-20 cm of new snow on Wednesday night. This new snow combined with the previous nights 30 cm brings the recent storm total to about 50 cm. The storm has been very mild, with freezing levels near 1800 metres on Wednesday. The temperatures started to fall early Thursday morning when the rain and snow moved out of the region. The winds have been very strong from the south and southwest. Expect to find windslabs on north and northeast aspects in the alpine and at treeline. There may be a rain crust developing below 1600 metres as the freezing levels drop back to valley bottom. The previous storm snow is now fairly well consolidated and makes for a generally strong mid-pack. A surface hoar layer buried around Christmas is well preserved, now buried around 80 cm below the surface and is producing sudden "pop" results in stability tests. A surface hoar/facet/crust interface from mid-December is also still preserved. This one is buried 100 to 150 cm deep and is still reactive to natural and human triggers. Despite sudden snowpack test results, triggering these weak layers is proving difficult; however bear in mind if anything did release on either of these layers, the consequence of the resulting slide would be large.

Problems

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.

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.

Cornices

Cornice Fall is the release of an overhanging mass of snow that forms as the wind moves snow over a sharp terrain feature, such as a ridge, and deposits snow on the downwind (leeward) side. Cornices range in size from small wind drifts of soft snow to large overhangs of hard snow that are 30 feet (10 meters) or taller. They can break off the terrain suddenly and pull back onto the ridge top and catch people by surprise even on the flat ground above the slope. Even small cornices can have enough mass to be destructive and deadly. Cornice Fall can entrain loose surface snow or trigger slab avalanches.