Click on video for a laugh. 15-20 cm of new snow, Thank you Frosty. Nice Christmas Dump. There have been bigger but that was very good skiing!! Not so sure about Ullr anymore. The Alpine remained closed for the day, should be epic for Boxing Day. Click here for the updated hazard rating: Avalanche Advisory

Merry Christmas

One whole cm recorded over night. Maximum temperature at 2260 meters was -3 at 18:00 Hrs Dec 24, and Max temperature of  0 at 1550 meters was at 0645 this morning. Freezing level stayed below the forecasted levels. With these strong zonal flows the weather models are not as accurate, off by 4-6 hours, or not even close.

Yesterday produced mostly size 1 avalanches with explosive and ski testing with a couple of size 2's on the larger start zones. Some areas remained closed due to the continuous redistribution of the snow over various surfaces.

Click here for the forecast and avalanche advisory: Weather Forecasat
 

Thanks to Darren Saul for contributing these images of a ski cut on the NE aspect of Vantage Peak in the Duffy Lake Region. The size 2 avalanche propagated from rock to rock, was 25 cm at the crown, the 30 by 50 meter slab ran about 300 meters.

Slab in motion

Shot of run out zone

Looking up the slide path

Toe of the avalanche. Forecasters have been talking about isolated wind slabs, here is a classic example. Luckily the party was very experienced, recognised the hazard and could perform an effective ski cut. Less experienced tourers may have been caught in the slide and with the amount of rocks evident in the slide path  it would not have been pretty.  As discussed in a previous post, once these pockets receive more load from the new snow arriving there will be many  more of these events. Click here for the updated hazard rating: Avalanche Danger Advisory

Finally, 11 cm of new over night and still falling (06:00 Hrs). freezing levels will rise through out the day and peak tonight to possibly 1700 meters. The freezing level will slowly drop back down tomorrow with continuing precipitation. The unwanted persistent high pressure ridge has finally succumbed to a zonal flow with the jet stream giving us some long overdue precipitation.

La Nina:  Everyone was hope full that this winter would be a repeat of last winter. The fact of the matter is that there have been past La Nina years that are very dry! This could be one of those winters. Its still early yet and only time will tell if we get back into a good cycle of low pressure systems giving us what we really want! A toast to Ullr might be necessary. Click here to find out about Ullr:  ULLR

Lenticular clouds moved in early this morning and then dissipated. The approaching front could finally be seen at the end of the day. The high pressure playing with our enthusiasm for snow and continuing to give us dry conditions. . For an explanation of lenticular clouds click here: Lenticular Clouds

Another amazing day in the mountains. The short days upon us have the best sunsets. Today  is the shortest day of the year. The high pressure is breaking down and the models are looking for snow starting on Friday.  Its -5 in the alpine with calm winds.

With new snow on its way this is the time to look at the terrain and know what it looks like before it is covered with 10 to 30 cm of fresh snow. The snow pack is thin and the surface the new snow will be falling on is hard in places and there are isolated pockets of wind slab in other locations. Even a size 1 avalanche can take you for a ride and if you hit rocks, the rocks win. Situational awareness is key to staying safe with the terrain being the dominant hazard. Play hard but be safe!

Not much to talk about as far as avalanche activity, so I thought we could discuss a misleading term that is open for interpretation. Rotten is used when we are describing crusts or old facets in the snow pack. Looked up the word rotten in several dictionaries and in the context of life sciences the definition is decomposing or decaying. Another definition is breaking up, especially through age or hard use. Earth sciences refers to it as soft or crumbling.

From Mountaineering, Freedom of the Hills, they have there own interpretation, "Rotten snow is a spring condition characterised by soft, wet lower layers that offer little support to the firmer layers above. Rotten snow forms when lower layers of depth hoar become wet and lose what little strength they have. It is a condition that often leads to wet loose-snow or slab avalanches running clear to the bare ground."


In the avalanche community we use the term often when we describe the old loose facets around rocks or when a crust starts to break down and we refer to it as rotting. I am sure you have read the avalanche bulletins and the word rotten has come up on many postings.

So, when we have decomposing stellars with lots of skier traffic do we have rotten snow?

At 06:00 Hrs the temperature at the Horstman Hut was -13 with light winds. The ridge will break down again on Friday.  The weather models are all trending to powder on Christmas Day.

The persistent East Pacific ridging continues to plaque us with little precipitation. The occasional weak front has slipped into our area with 20 cm of snow recorded for December. It appears there is a light at the end of the tunnel and by Christmas we may be into a more favourable weather pattern. Hopefully we will see snow on Friday morning, with more to follow into the new year.

Not a lot of development in the Valley.

Thank you to Cliff Jennings for sharing these pictures of a cornice blast in Back Bowl on Whistler Mountain. 

The mountains received 8 cm of new snow last night, temperatures dropped and the freezing level is around 1000 meters. Avalanche control on Blackcomb Mountain has been getting size 1 isolated pockets of wind slab. Click here for the latest Avalanche Hazard Advisory: Advisory

Toni Sittlinger Photo: Earlier in the season we were talking about depth hoar. Here is an example. Not exactly weather today for developing depth hoar, warm temperatures in the alpine with strong winds. I asked what the avalanche conditions were today and was given a very descriptive term "Pasted pockets of wind slab".  There are pockets of up to 30 cm of wind slab.  For the updated avalanche advisory click here. Advisory

For a great read and if you are interested in improving your skiing check out this book written by Ken Chaddock. Click here for more info: Improve your skiing

Yesterday was one of those amazing days.The  Kokanee Series started with a bit of fresh snow but great race conditions. Another whole centimetre fell last night with much the same for the weekend. Refer to yesterdays  post on sluffing. Will likely be more of that today.

This picture of the pump house at Horstman Creek was taken this time last year (Dec 15, 2010).

It is finally snowing, not much but enough to make the surface we so enjoy a tad softer. We received 6 cm over night at the Pig Alley weather plot. The next few days will give us snow showers to light snow. Every centimetre counts. 

You can expect to get sluffs to move today on steeper terrain. Click here: Definition of a sluff

The high pressure finally broke down yesterday allowing the first low into our area in a long time. Not much precipitation associated with the clouds but for now the high has been pushed to the south.

The grooming yesterday in Lakeside Area provided great skiing with 1 cm of new contributing to soft corduroy.  Even a centimetre can help the snow quality.

Cliff Jennings photo of Mt. Neal on the Duffy lake Road taken yesterdeay. Very large slide with a crown line that is 3 weeks old. We have been in a draught!!

If you are looking for fresh tracks Alta Lake was the place to be on the week end. The high is finally breaking down, several low pressures are approaching the coast from the north, the first one is weak but the second one could give us a bit of snow. There is a Kokanee race on Blackcomb this Thursday, last years statistics for snow on a  race day were very high. A melt freeze crust is prevalent in the alpine, will be interesting if and when we get a significant load on that layer. The avalanche danger scale is at low for all zones.

Hazard Acceptance        Risk Tolerance          Hazard Analysis             Human Factors

This picture was taken prior to all the new terminology used in the avalanche world. Risk tolerance is a term used in Finance, in the Avalanche industry it is a relatively new, commonly used term.  A hazard is defined as a "Condition, event, or circumstance that could lead to or contribute to an unplanned or undesirable event". Human factors is another term which started during World War II when pilot and machine had to become one!!  Hazard analysis is used as the first step in the process to assess risk.


This individual is skiing a south west exposure at the end of the day in a shallow snow pack above a cliff band with no companion. The photographer is a fair distance away, patrol has long gone for the day. This individuals acceptance of exposure to potential hazards is very high.

In my career I have gone to many avalanche incidents where the individual has been badly injured or killed. Ironically most of those individuals had just completed their CAA Level 1 course. The new terminology is very important and everyone should pay attention. Play hard but be safe!!!

Thanks to Jeff van Driel for this video of the propagation saw test discussed on the blog,  December 8, 2011.

Not the best place to be!! Might have been an unpleasant ride into the rocks if it were just a bit bigger. From the photo think about this skiers decision making process. Will post my thoughts tomorrow.  Perhaps some Kodak courage!

Nigel Stewart Photo: Taken up on the ice cap on Thursday December 8, 2011.

Nigel Stewart photos: Debris from the natural cycle we had November 22, 2011. Certainly tells the story about how much snow we have had in the past 16 days.

Amanda Taylor Photo: Surface Hoar from the Cerise Creek Trail. The perfect place for surface hoar development, no sun, surface temp -6 and a water source near by.

Amanda Taylor Photo: At least the conditions in the Alpine are not producing surface hoar this large. Would be nasty if and when we ever get more snow.  Possible flurries tonite, maybe 2 cm, then another 10 cm for Tuesday morning but this high pressure systems will dominate for a bit longer. Dry conditions are expected through out next week.  The snow pack has tightened up and continues too.

Spatial Variability: I tried to look up this definition in the Websters Dictionary sitting on my office bookshelf. Published in 1988... no definition!!  Today looking up the same term on Wickapedia: Spatial Variability occurs when a quantity that is measured at different spatial locations exhibits values that differ across the locations. This picture is older than my dictionary,  the slope is just above the top station of Jersey Cream chair circa 1982. The road from 7 Th Heaven to the top of JC lift is now here. Who would have thunk!  If you look up the definition on the Bilingual site of the CAA it is on page 211, scroll down, Click: Spatial Variability  There is much to learn about avalanches and travelling in the back country certainly has its risks. Digging a pit and feeling confident about the slope should be one of many considerations.  This definition is important!!

Jeff van Driel Photo and Observations. A pit displayed on the new App PitPod below:

The tests performed are the Compression test and the Propagation Saw test (PST) For an explanation of the compression test click here, scroll down: Compression test It will be listed in the glossary. The Propagation saw test is explained in this link: Propagation saw test

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.