Avalanche Forecast

Issued: Nov 30th, 2015 9:05AM

The alpine rating is moderate, the treeline rating is moderate, and the below treeline rating is low. Known problems include Wind Slabs and Deep Persistent Slabs.

ghelgeson, Avalanche Canada

South Columbia.

A big change in the weather is headed our way. Tuesday is the probably going to be the last day you can confidently get after it in big terrain for a while.

Summary

Confidence

Poor - Timing, track, or intensity of incoming weather system is uncertain

Weather Forecast

Bottom Line: The weather is changing, the inversion should be cleared out by Tuesday morning. The coast will likely get hammered as a digging upper trough makes landfall over the next few days. Some of the snow and southerly winds associated with this event are expected to spill over into the Southern Columbias. At this point amounts and timing are too dynamic to pin down, but the region should see 2 to 15cm of snow Tuesday night, with an additional 5cm Wednesday. Strong SW winds are expected throughout the region beginning Tuesday night. The freezing level should remain at valley bottom until Thursday when its expected to climb to around 1500m. For detailed mountain weather information visit: avalanche.ca/weather.

Avalanche Summary

Natural loose dry avalanches from size 1.5 to 2 were reported from alpine features facing North, Northeast, East and and Southeast over the weekend.

Snowpack Summary

The snowpack is extremely variable at this time, with wind scoured North facing slopes at treeline and above. South facing slopes have wind slabs at tree line and above, and may be hiding surface hoar from the previous spell of cold clear weather. Surface facetting has been observed in the region as a result of the recent cold weather and clear skies, and surface hoar up to 20mm has been reported in sheltered locations below 1900m. There are a number of surface hoar layers now buried in the snowpack that at present have been unreactive, with the most recent buried on Nov 24th. In shallow snowpack areas especially on northern aspects, there are reports of weak facetted layer at the base of the snowpack. With the recent warm temperatures, expect sun crust on solar aspects above 1500 metres.

Problems

Wind Slabs

Previously strong north winds formed wind slabs that extend from treeline to just below ridge crest. Most of these wind slabs are probably old, tired and hard to trigger, but there may be a few that remain sensitive to human triggering.

Be cautious as you transition out of wind sheltered terrain and avoid features that are actively being wind loaded.>It's best practice to use ridges or ribs to avoid pockets of wind loaded snow at this time.>

Aspects: North, North East, East.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 3

Deep Persistent Slabs

We suspect that this is really only a problem on high elevation north facing features where weak faceted snow *may* exist at the base of the snowpack.

You can manage this problem by avoiding likely trigger locations in the alpine like rock outcroppings, convexities and places where the snowpack goes from thick to thin.>

Aspects: North, North East, East.

Elevations: Alpine.

Likelihood

Unlikely

Expected Size

3 - 6

Valid until: Dec 1st, 2015 2:00PM