Avalanche Forecast

Archived

Nov 25th, 2015–Nov 26th, 2015

Alpine

Natural avalanches unlikely, human triggered possible.

Treeline

Natural avalanches unlikely.

Below Treeline

Below Threshold.

Alpine

Natural avalanches unlikely, human triggered possible.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Below Threshold.

Alpine

Natural avalanches unlikely, human triggered possible.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Below Threshold.

Regions

Sea To Sky.

The snowpack is extremely variable depending on aspect and elevation and does not adjust well to rapid change. Watch for rising temperatures to well above 0 degrees. Check out the Mountain Information Network. Give info, get info!

Confidence

Poor - Due to the number and quality of field observations

Weather Forecast

The high pressure ridge continues to dominate the coastal regions. Strong alpine temperature inversions will be prominent and freezing levels will be rising to 2400 m. Moderate to strong outflow winds will prevail in coastal valleys especially in the overnight and early morning. Valley cloud may accompany the strengthening temperature inversion. By Sunday the weather pattern may see a change, however; timing and intensity of the next Pacific system is hard to pin point due to disagreement between the Canadian model and the GFS.

Avalanche Summary

On Tuesday, a size 1 skier triggered slab was reported from an east aspect @ 1900 m as well as numerous natural wind slab avalanches from southerly aspects up to size 1.5. I suspect these stiff wind slabs may remain sensitive to rider triggers and as the warm air aloft invades the region watch for obvious clues like natural avalanche activity and moist/ wet snow surfaces, especially on southerly slopes. Smaller avalanches may also trigger deeper layers beneath the the surface, initiating larger avalanches.

Snowpack Summary

Monday's 20 cm of storm snow has seen some serious effects from the recent winds and cold temps. Northerly winds have likely built stiff wind slabs on southerly slopes and stripped snow from exposed aspects. These wind slabs may have a poor bond to the old surfaces that comprise of surface hoar, crusts (potentially up to 2100 m) and some dry facetted snow above that. Strengthening temperature inversions at upper elevations may start to deteriorate the upper snowpack, especially on southerly aspects. Watch for obvious signs of instability like moist and/or wet snow surfaces and snow balling. Where the buried crust is thick, avalanches failing on deeper layers beneath have become much less likely. My uncertainty lies at higher elevations where the buried crust doesnt exist and deeper persistent weak layers may. Reports indicate that these shears are resistant in the moderate to hard range with sudden fracture characteristics. I'd remain extra cautious as they may be sensitive to rider triggering.

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.

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.