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Avalanche Forecast

Archived

Feb 3rd, 2021–Feb 4th, 2021

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

South Coast Inland.

Fresh snow and wind may build increasingly reactive storm slabs throughout the day.

Some areas may see enhanced snowfall amounts of 15-20 cm. Pay attention to changing conditions and be prepared to dial back your terrain choices if you see more than 15 cm of new snow.

Confidence

Moderate - Forecast snowfall amounts are uncertain.

Weather Forecast

WEDNESDAY NIGHT - Mainly cloudy with a few flurries / moderate to strong west wind / alpine low temperature near -10 

THURSDAY - Flurries, 5-10 cm, with the potential for some isolated enhancement bringing 15-20 cm to some areas / strong northwest wind / alpine high temperature near -7

FRIDAY - Mainly cloudy with a few flurries / moderate northwest wind / alpine high temperature near -6 / freezing level 1300 m 

SATURDAY - Mainly cloudy with flurries, 5 cm / moderate west wind / alpine high temperature near -7

Avalanche Summary

Human triggered avalanches will remain likely on Wednesday, especially in wind loaded areas at higher elevations. 

There were a few reports of size 1-1.5 natural and human triggered avalanches in the region on Tuesday.

There were several reports of size 1-2.5 natural, human and explosives triggered avalanches in the region on Monday. It is suspected that some of these failed on the recently buried persistent weak layer.

There were several reports of size 1-1.5 natural and human triggered avalanches in the region on Sunday.

Snowpack Summary

5-10 cm of snow is expected throughout the day on Thursday, though some areas may see isolated enhanced snowfall amounts of 15-20 cm. Moderate to strong northwest winds will likely form reactive slabs in the alpine and open treeline areas.

30-60 cm of recent fresh snow sits on a persistent weak layer that consists of facets at upper elevations, surface hoar in sheltered areas, a melt-freeze crust below 1600 m, and a sun crust on south-facing slopes. 

In the south, the underlying snowpack is well consolidated. In the north, a melt-freeze crust from early December may be found 100 to 200 cm deep. Recent reports suggest that this layer is gaining strength and it has been unreactive in recent weeks.

Terrain and Travel

  • Watch for changing conditions today, storm slabs may become increasingly reactive.
  • Avoid freshly wind loaded terrain features.
  • Be aware of highly variable recent wind loading patterns.
  • Be aware of the potential for large avalanches due to the presence of a persistent slab.

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.