Avalanche Forecast

Archived

Nov 24th, 2013–Nov 25th, 2013

Alpine

Natural avalanches unlikely, human triggered possible.

Treeline

Natural avalanches unlikely.

Below Treeline

Natural avalanches unlikely.

Alpine

Natural avalanches unlikely, human triggered possible.

Treeline

Natural avalanches unlikely.

Below Treeline

Natural avalanches unlikely.

Alpine

Natural avalanches unlikely, human triggered possible.

Treeline

Natural avalanches unlikely.

Below Treeline

Natural avalanches unlikely.

Regions

Kootenay Boundary.

This bulletin was created using very limited field data. Significant variation in snowpack structure is likely to exist across the region. If you are out in the mountains, please send your observations to [email protected]

Confidence

Poor - Due to the number of field observations

Weather Forecast

An upper ridge of high pressure dominates until Tuesday resulting in dry conditions, light alpine winds, and mostly sunny conditions. A temperature inversion exists over most of the Kootenay-Boundary region with a layer of warm air sitting at mountain-top elevation. On Wednesday a weak upper trough will replace the high pressure system causing increased cloud cover and the possibility of light snowfall.

Avalanche Summary

We have received limited reports of pin-wheeling and small loose snow avalanches releasing on steep, sunny aspects during afternoon warming.

Snowpack Summary

80-110cm of snow is typical at treeline although observations are limited and this amount may vary across the region. Roughly 60 to 70cm of well settled storm snow is now sitting on the October crust located just above the ground. Little is known about the reactivity of this crust; however, limited reports suggest that the crust interface is well bondedThe current temperature inversion is causing the snow surface to melt in the alpine. Sun exposed slopes are undergoing daily melt-freeze cycles. A surface crust is also being reported below 1700m. Large SH is forming on all aspects but is melting on south aspects during the daytime warming. If you are traveling in the mountains, now is a good time to make note of these surface conditions which may become persistent weak layers once buried by new snow.

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.

Loose Wet

Loose Wet avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.