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.

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!!

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.

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.

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.

• A picture of surface hoar which will likely form this evening as the temperatures drop.
• It snowed 11 centimetres at 1550 meters today, which improved the skiing. More explosive testing today resulted in size1 to size 2 slides occurring in the storm snow. A notable event that happened today was a solo skier involvement in a size 2 avalanche, hiking up a steep slope injuring himself and skiing back into the boundary to summon help for a large thigh contusion. The hazard rating was at considerable, if you are not sure what considerable is find out on the links below or click here and click on the description of  the hazard rating. Considerable
• If you are planning to go into the back country please!!! do not travel alone, have the appropriate gear (transceiver, shovel, and probe) and learn how to use it in companion rescue.

 

Another active day on the mountains, avalanches from Size 1 to Size 4 were controlled by hand charges and heli-bombing today. This is a shot of Blackcomb Bowl were a hand charge released a size 3 avalanche.

The largest result from heli-bombing on Blackcomb was the bowl referred to as Corona, it was released by a 2 Kg charge deployed on the skiers lt side, the entire bowl released, the largest avalanche I have known off in the past 32 years for this slope. (Click to see video above) I believe it is a size 4 considering the fracture line was from 1.5 meters to 3 Meters in depth.  The initial avalanche pulls out the steepest slope then the entire bowl releases going across the valley and uphill. Many large avalanches were released on Whistler as well, Flute, Glacier Cirque, Exiliration, are just a few. If you are up in the next few days its a good idea to take note what has slid and how big the results are. At the end of the month I hope to compile images and a summary of the events from a very active November.

Ryan Bougie Image

At 1850 meters 20 Cm of dry fist snow. Above 15 moist 4f. Above dry 1f. Cte 3 Pc down 20. Ctm 12 Pc down 35.

Ryan Bougie Picture: As you can see there is not much visual reference at this time. A size 2 was observed out of low test with explosive testing this am. In the past 24 hours the temperatures spiked to maximums at 17:00 on Saturday November 26 Th. Horstman Hut at 2240 Meters was -1.2 and at the Catskinner weather plot 1550 Meters it was +2.4. Winds in the alpine over the past 24 hours have been averaging at  65-85 Km per hour with gusts up to 150 Km per hour. The Catskinner weather plot had 1 centimeter of new snow this morning while the Pig Alley weather plot at 1650 meters had 10 centimeters. Pig Alley Precipitation gauge is registering 50 Millimeters at this time 11:00 for the past 24 Hours.. The temperatures are cooling off and it is snowing at the bottom of the Solar Coaster Lift on Blackcomb. Temperatures at this time 11:00 are -4 at 2240 Meters and 0 at 1550 Meters. The forecast is calling for clearing this afternoon, flurries for a few days than sunny and warm. Many people are commenting about terminology, it is available at the CAA site listed at the bottom of the page, but here is a quick link to Avalanche Size Classification:
www.avalanche.ca/cac/library/research-and-articles/Avsize
Present Avalanche Conditions 

Fresh snow , sunshine and some great skiing on Friday Nov 25. Avalanche control produced more slides on both Whistler and Blackcomb. Size 1 to Size 3 . The next 2 days will produce significant load again and there should be some good results. The snow pack is about as complicated as I have seen it in my career.  In this shot if you look closely you can see a size 3 on Little Whistler. If you are venturing into the backcountry please read the advisory.    Click on this link.                 Present Avalanche Conditions

Fracture line Profile in Bushrat Blackcomb Mountain Nov 25

Add caption

All the kids were out playing yesterday, the snow was great, Blackcomb opened, Merlins opened, although no one was sitting outside. Pig alley was at 16 cm of new snow this am, it should be another great day on the hill. Not many results or stories about avalanche activity but I am sure with the load we will get from Saturdays storm that will change. Freezing levels could go up to 1700 meters, not good news for the snowfall but may help with our present avalanche conditions. Please check the CAA site and Whistler Blackcomb site for hazard updates.

A short clip from Heli Bombing on November 22, 2011. The slope is referred to as Shrund Alley, a 2 Kg shot was deployed. Good result for this particular slope. On November 23 more explosive testing was conducted on Blackcomb with little results. Another 15-20 centimeters is expected today and a juicy storm coming on Saturday. The hazard rating is still high and with more load things will get active again. Click here for the up to date hazard rating

One of many natural avalanches which occured on November 22 below the tree line and in the alpine terrain. Natural size 2 to size 3 were observed in many start zones with some avalanches running full path. This shot is just above the top of the Wizard Chair on Blackcomb Mountain on Freefall. This slide occcured in the new snow layers. Helicopter deployment of 2 kg charges yesterday on Blackcomb produced size 1 to 2.5 size avalanches. With almost a meter of snow in the past 48 hours some of the large avalanches were stepping down from new snow , down to the November 12 Th crust and then down into the Halloween crust. Crown lines as deep as 2.5 meters were observed. 

Its snowing hard, if you think your getting out of town on a motorcylce forget it!!! Its time to ski. Looks like the temperatures are warming but the snow is still pounding. Should put a good load on our complicated snowpack, results to follow tomorrow. Enjoy the POW.

I