6 Dec 2011

Persistent Weak layers: This picture shows the formation of the December 4, 2007 crust which was very active,  went to sleep, woke up went dormant and then woke up again on May 17 th and produced some very large Spring Time  Avalanches. The temperatures went to + 17 degrees on that day and there were several large events in the Whistler  Area. When this crust formed it rained to 2200 meters, the rain percolated down about 40 centimetres into the new snow and accumulated on a buried surface hoar layer. That winter was a prime example of a snow pack with a  Persistent weak Layer. Click here to see the definition of PWL. Persistent weak Layers
This result occurred 163 days after the formation of the crust.

5 Dec 2011

A commonly used metaphor in the Avalanche Community is Bridging.

The picture above is taken at sunrise this morning from Coal Harbour. As I sat by the sea I could not help but reflect on this metaphor and its lack of a formal definition in any Avalanche Glossary.

I was curious about this oddity and upon my arrival back in the mountains this afternoon,  I reached out to some members of our community; an Engineer, some Back Country Skiers, and some Avalanche Technicians.

I talked to a Mountain Doctor. a  Lawyer and some Avalanche Chiefs .

Their responses varied but not by much!

A bridge in the snow pack is a vertical and horizontal element... a layer that adds a cohesive strength  above the under lying weak layers in the entire snow pack. Some snow scientist avoid the terminology................. its a touch..... intuitive.

That's another topic altogether?

Please share your thoughts as this is a very cool subject!!

4 Dec 2011

Present conditions are ideal to form surface hoar. In the past few weeks there has been much discussion on buried surface hoar layers. Click on this link to understand its formation. Surface Hoar

For the latest hazard rating click here: Hazard Rating
Rob Withey Photo: Unfortunately there was condensation on the lens but Rob reported a Sz 3+ that ran last Sunday on the west aspect of the ridge on the way to the Wendy Thompson Hut. The slide ran full path, destroyed trees, turned left at the valley bottom where the skin track leads you to the hut.

3 Dec 2011

For now the snow pack has tightened up and there appears to be significant bridging. The hazard rating is trending to Moderate. Click here for scale.Hazard Rating Read the description carefully. Skiers are unlikely to initiate a large avalanche but a snowmobile still has enough weight to possibly trigger the deep weak layers still present in the snowpack.

1 Dec 2011

Jorli Ricker Photos of Grizzly Lake and Choclate Bowl taken on November 30, 2011. Everyone out on sleds this weekend should read the bulletins and be safe. I am sure there were many natural avalanches last week in this area but with the snow pack the way it is use caution when your out there. There is a trend for better stability but I would be wary of any lurking surprises. We still have a very complicated snowpack.

Reverse loading was the new challenge yesterday. North to North East winds transported snow resulting in a stiff wind slab. Ski cutting produced a 1.5 yesterday morning.  These shots were taken last February 20, 2011 by Braden Douglas ski touring on the East Ridge of Fissile. Skinning up released this slab, a sphincter tightening moment.  North winds had been blowing for a couple of days before this event.  We are in for a few days of inverted temperatures and North  to North East winds. The new snow has bridged over some of the deep persistent weak layers but in shallow areas there is certainly potential for large releases.Click here for latest update.Hazard Rating for Whistler area It will be interesting to see how the snow conditions do with the forecasted temperatures in the Alpine over the next few days. If anyone has pictures or stories from the past month please pass them along. Send to wwflann@me.com. Be sure to check out the posts from November to keep you updated on what has been happening in the snowpack. Check out Cliff Mass weather blog at the bottom of the page for his take on this large high pressure system.