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 9th, 2021–Jan 10th, 2021

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

Regions

Northwest Coastal.

  

New snow and extreme winds will form widespread storm slabs reactive to human triggers. Hazard may rise rapidly to HIGH in areas that receive more than 20 cm of new snow.

Confidence

Moderate - Uncertainty is due to the timing, track, & intensity of the incoming weather system. Forecast snowfall amounts are uncertain.

Weather Forecast

  

SATURDAY NIGHT: Snow; 10-20 cm. / Extreme, south ridgetop wind / alpine low temperature -8 / Freezing level 400 m.

SUNDAY: Snow; 10-15 cm, with another 20-30 cm. overnight / Extreme, south ridgetop wind / alpine high temperature -3 / Freezing level 1000 m.

MONDAY: Snow; 10-15 cm. / Strong, southwest ridgetop wind / alpine high temperature -5 / Freezing level 800 m.

TUESDAY: Snow; 15-20 cm. / Extreme, south ridgetop wind / alpine high temperature -4 / Freezing level 900 m.

Avalanche Summary

A few naturally triggered wind slabs up to size 2 continue to be reported. Additionally, there have been numerous recent reports of "whumphing" (collapsing) on a weak layer of surface hoar down around 100 cm. See recent MIN reports HERE.

Avalanche activity is expected to increase on Sunday as new snow and strong winds build fresh storm slabs.

Snowpack Summary

A non-stop series of storms has deposited 75 to 150 cm of new snow since New Year's. The amount of snow, as well as the wind speed and direction, has been highly variable between different drainages over this period, so there is uncertainty about exactly what the upper snowpack will look like as we come out of this storm. However lingering storm and wind slabs will likely need a few days to stabilize.

Aside from this new snow, the main concerns vary throughout the region. In the Shames area, this new snow has been bonding poorly to a surface hoar and crust layer that is now an estimated 75-125 cm deep. A bit further north in the Nass/Sterling/Beaupre areas there is potentially still concern about an older weak layer of surface hoar and crust that is now roughly 150 cm deep. In the far north of the region there is concern about weak snow at the bottom of the snowpack. At this point there is some uncertainty about whether these layers will still be reactive after such an intense stormy period.

Terrain and Travel

  • Avoid all avalanche terrain during periods of heavy loading from new snow and wind.
  • Watch for rapidly changing conditions during periods of heavy loading from new snow, wind, or rain.
  • Be aware of the potential for large avalanches due to the presence of a persistent slab.
  • Storm slabs in motion may step down to deeper layers resulting in large avalanches.

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.