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

Nov 28th, 2018–Nov 29th, 2018

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.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely, human triggered possible.

Regions

South Columbia.

The snowpack will likely need more time to adjust to the recent load of storm snow. Uncertainty exists around the buried, weak surface hoar layer. We suspect the potential for human triggered avalanches remain high.

Confidence

Moderate - Due to the number of field observations

Weather Forecast

The weather trend will start to stabilize as a high pressure system sets up through the forecast period. THURSDAY: Mostly cloudy with new snow 5-10 cm/ alpine temperatures near -4/ generally light winds from the SSW/ freezing level 1300mFRIDAY: Cloudy with sunny periods with a trace of new snow/ alpine temperatures near -9/ ridgetop winds light from the West/ freezing levels 900 mSATURDAY: Mix of sun and cloud/ alpine temperatures -9/ ridgetop winds light from the southwest/ Freezing levels near 800 m

Avalanche Summary

Avalanche activity spiked with the recent storm. This initiated a natural avalanche cycle up to size 2 on most aspects. Reports from the field also noted remote (from afar) human triggered avalanches up to size 1.5. By using explosives, commercial operations were able to trigger larger more destructive avalanches up to size 2.5, mostly on northerly aspects at upper elevations.Natural avalanche activity may taper off as the weather pattern becomes more stable. As the snowpack adjusts to this recent load, it's likely that human triggered avalanches will be the name of the game.Last Saturday (before the storm), a human triggered size 3 avalanche was reported in the region. This avalanche likely ran on the October crust, as it was reported as a full depth avalanche. Two reports on this avalanche can be found on the Mountain Information Network.

Snowpack Summary

The storm that arrived earlier this week distributed 40-80 cm of new snow by Wednesday morning. The higher accumulations were found in Monashee mountains. This snow sits on a weak layer of surface hoar (feathery crystals) and sun crust on steep south facing slopes. The surface hoar is widespread at treeline and below, but it may be found in sheltered alpine areas.At the base of the snowpack is a crust that formed near the end of October. This crust has shown limited reactivity in the South Columbia region, but with recent additional snow, high winds and warm temperatures, this layer could come into play.Snowpack depths taper quickly with elevation, many areas have over 200 cm in the alpine, between 100-170 cm at treeline, and 10-100 cm below treeline.

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.