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

Dec 8th, 2011–Dec 9th, 2011

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

Regions

South Rockies.

Confidence

Fair - Due to variable snopack conditions

Weather Forecast

A strong ridge of high pressure remains anchored off the BC coast & will continue to influence the region through the weekend. The good news is that the ridge begins to break down early next week which means that conditions will be more favorable for snow in the interior ranges. For Friday, winds will continue to be out of the W-SW at light to moderate values. We'll see a slight temperature inversion in the Alpine Friday, but I'm not expecting anything too dramatic. Freezing levels should creep down to at least 800m, likely a bit lower on Friday night. Mostly sunny skies are forecasted for Friday with a daytime high of -4 @ 1500 m & an overnight low of -15. Saturday looks very similar with a smidge more cloud building into the region.

Avalanche Summary

We have a report of a large avalanche (size 3.0) triggered by a snowmobiler in the Mt. Corbin area last weekend. In short, it sounds like like some snow stiffened by the wind released down deep on the weak facets. There have been numerous avalanches both natural and human triggered from Size 2 - 3 in the adjacent forecast areas where avalanches have been failing near the ground on the crust/facet combo. If you have any observations from the field, please drop us an email: [email protected].

Snowpack Summary

We're off to a good start for early December with upper elevation snow depths that average a meter. It's been about 10 days since our last significant storm and since that time the snowpack has suffered an unrelenting barrage of wind from around the compass rose. Wind exposed terrain is now a mixed bag of wind effected snow that varies from old hard windslabs to fresh small windslabs and everything in between. To travel safely at & above treeline you need to be able to recognize and avoid these potentially dangerous windslabs. This is the first part of the avalanche problem. Folks with extensive experience and education should be able to manage this hazard.Getting a little lower in the snowpack reveals some ugliness. A raincrust sits above large striated facets (sugar snow) on the ground. This is the classic Rockies house of cards setup that professionals throughout the region are concerned about. While there hasn't been any activity reported on this layer for the last few days, the potential for large full depth avalanches remains a concern for backcountry travelers. Triggering an avalanche in this weak layer will result in a large & destructive avalanche that will likely be unsurvivable.This problem will not go away anytime soon. If I was putting together plans for the weekend I'd be combing through my terrain atlas (google earth) looking for slopes around treeline that are protected from wind. Once you're out in the field stay off of terrain features that are thin and weak. Rock's and/or tree's poking out of the snow are a good indication of thin weak snow. It's good practice to avoid terrain that is steep and rocky in general right now. Remember, it's only December and our snowpack needs some time to mature before we even start thinking about the bigger more committing terrain.

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.

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.