Weekly report from HAT - 06/12/07
The snow arrived ..... finally. Last week we told you it would snow at the weekend. What actually happened was it started snowing on Sunday evening at 20.00 and did not stop until Tuesday lunchtime, so the situation is quite transformed and the best we have seen it in early December for 10 years. (see our snow depths tracking page)
Snow news
That is not all, The snow is forecast to come back with a vengeance this weekend and especially on Sunday. Temperatures may fluctuate considerably bringing rain below 2000m for a while. But there will also be snow down to 1000m at times. This makes it very uncertain how stable the resulting snow pack will be, we will need to study the bulletins to get the opinion of the experts. Large falls of snow in a short time tend to be unstable, but fluctuating temperatures will stabilise the pack more rapidly. The situation is further complicated by the very high winds. which has stripped some higher exposed places and dumped the snow in others creating wind slab.
There was also some surface hoar and evidence of a breakdown of the snow pack before the last snowfall. So be careful, study the bulletins (on our web logs.) and read ski diaries from Henry and Wayne Watson of Alpine Experience.
New information services
We have completely revamped our web based information services. In addition to this weekly ezine, there are now 4 new blog sites. Henry's ski diary - see Henry's discussion of what it is like out there. Val d'Isere - updates on current conditions, photo albums and avalanche forecast translations. Chamonix - updates on current conditions, photo albums and avalanche forecast translations. HAT blog - posts of the ezine articles on avalanche awareness and general HAT news.
Each week in this ezine you will find an update on the snow conditions, avalanche awareness tips, weather forecasts, and a translation of the Meteo France off piste safety bulletin.
Looking forward to catching up.
Future ezines will be on Thursdays - next one on 15th December.
Regards - Chris Radford - HAT ezine editor.
Tip of the week
You will know that we expect all off piste skiers to read the avalanche bulletin and understand the risk level that is present on each day. This week's tip is about understanding the avalanche bulletin and interpreting the risk level.
Today, you will see the risk is described as Marque, or Considerable which is level 3 on a scale of 1-5.
To help understand this, we have published in this ezine two versions of the scale for your study. There is one published by Sport Scotland Avalanche information service which is written in English in its original form. There is also a translation of the French scale published by the ValdIsere authorities.
At our session with our technical director this week. Alain Duclos explained one of the risks you can manage if you know the hazard rating.
Avalanches usually only happen on slopes above 30 degree slope angle. But there is a quite significant risk that you can trigger an avalanche on a steeper slope above you, even if you are on a slope that has a gentle slope angle that is lower than 30 degrees.
This risk is magnified when the rating is higher.
Risk level 1 - you cannot trigger a slope that is above you. you can only trigger a slide on slopes that are greater than 30 degrees and then only in a few places.
Risk level 2 - it is highly unlikely you could trigger a slide, if you remain on slopes with a lower angle than 30 degrees.
Risk level 3 - it is quite likely you can trigger a slide on a slope above you even if you are on a slope angle that is less than 30 degrees. So make sure you go one at a time.
Risk level 4 - You should keep well away from slopes above 30 degrees. If the slope has a weakness and you ski underneath it, you could set it off. If you have to risk it, then ski one at a time and make sure the group clusters around islands of safety.
This is another way you can use the hazard rating scale.
