SCARPA Athlete Richard Bentley is one of Scotland's best known Winter Mountaineering and Climbing Instructors, so he knows a thing or two about avalanches and how to understand them..
In this blog Richard takes us through using the avalanche forecast and how to safely plan an prepare for a Scottish Winter trip.
Avalanche hazard awareness and using the avalanche forecast in the Scottish Mountains.
Throughout the Winter (from 14th December until mid April) the Scottish Avalanche Information Service (SAIS), (www.sais.gov.uk), publish daily avalanche hazard reports for 6 popular areas. These areas are:
- Creag Mheagaidh
- Northern Cairngorms
- Southern Cairngorms
For anyone heading into the Scottish Winter mountains, reading and understanding the avalanche forecast is an essential part of planning and preparation before heading out.
The theory and mechanics of understanding avalanche hazard can be complicated, if you choose to delve into it in a deep way.
However, we can also choose to keep the understanding simple and clear by making sure we read and understand the important parts of the avalanche forecast, and this is what this short article aims to help you do.
Grab a coﬀee, open up the SAIS website, whilst you read this article, and lets look at a typical forecast page.
1. What is the level of the avalanche hazard ?
2. Where on the mountain is this Hazard ?
3. What are the avalanche “problems”, that are causing this Hazard ?
4. When during the day is the Hazard greatest ?
1. What is the level of avalanche hazard ?
Here we can see the avalanche hazard is Considerable, indicated also by the orange colour.
To understand what this means the scale is explained as follows:
Some important points to note regards the level of avalanche hazard are:
- Due to the size of the Scottish mountains we never reach the “Very High” Therefore, to all intents and purposes its is really a scale from “Low - Moderate - Considerable - High”
- A Low hazard means there is still a risk of a small or medium avalanche that could injure i.e. there is still a hazard !
- Most human triggered avalanche incidents and accidents occur when there is a Moderate, or Considerable
2. Where on the mountain is this avalanche hazard ?
The pictorial “Hazard Compass Rose”, indicates where on the mountain the forecast hazard is. The words in the “forecast snow and stability hazard” will also re-enforce this and add important detail.
“New snowfall and redistribution of existing soft snow will continue to deposit unstable windslab in sheltered areas throughout the period.
Greatest accumulations will be on North through East to South-East aspects above 850 metres, where avalanches are likely.
Fragile cornices will build above these aspects. The old snowpack where exposed will remain hard and icy. The avalanche hazard will be considerable.”
Some important points of note regards the location of the hazard are:
• The words will often give a more accurate and detailed picture than the picture itself. Read them first.
• This not only tells you where the Hazard is, but also, where it is not ! ( In this case South West and West aspects) i.e. it tells you the safer ways up the mountain.
3. What are the avalanche “problems” causing the avalanche hazard ?
We now know the level of hazard, and where on the mountain it can be found. Now we can see what is causing this Hazard, by looking at the avalanche problem. These will be described in the words of the report, and also by the icons, which you can click on and get more information.
For this example, the words say:
“Will continue to deposit unstable windslab”. “Fragile cornices will build above these aspects.”
At the top of the page, these avalanche problems are illustrated pictorially, and you can click on the pictures for more detail.
The icon on the left above, represents “Windslab. A common problem in the Scottish Winter mountains.
Here is the explanation you can find if you click on the “problem”
“ Weaknesses developing in the snowpack due to wind transportation of snow and the formation on windslab”
A more in depth description of these “avalanche problems” can be found on the SAIS website.
Some important points of note regards the type of avalanche problem:
• Some types of problems are relatively obvious and have a lot of visual clues you can see in the mountains. For example, a lot of drifting snow, large cornices forming, large pillows of snow building up in sheltered areas.
• Some types of problems are less obvious, particularly those related to Temperature. Very cold temperatures can lead to “Hidden” weaknesses developing within the snowpack. Similarly, sudden rises in temperature can quickly weaken the snowpack.
4. When during the day is the avalanche hazard greatest ?
A final consideration is the dynamically changing nature of the avalanche hazard. The forecast covers 24 hours, from 6pm the day it is issued, to 6pm the next day.
The Hazard given will be for the peak hazard expected during that period.
Rapidly changing weather patterns, are common, and can lead to rapidly changing hazard levels in the mountains, both good and bad. The words in the report will give this information.
Some examples may read as:
“On these aspects cornices will become increasingly unstable especially during the afternoon.”
"The snowpack will slowly consolidate during the day due to a slow rise in temperature”
The best way to develop an increased understanding of the avalanche hazard in the Scottish mountains is to thoroughly explore and read the SAIS website, and forecasts.
There is a lot of education and informative articles on the site, in addition to the daily forecasts. This information explains some of the issues mentioned in this brief article in far more detail. I’d encourage everyone to dive in and learn.
Another good resource is the European Avalanche Warning Services www.avalanches.org. Here you will find explanations of all the terminology and further education on hazards scales and problems.
The bottom line: Don’t head into the Scottish winter hills without reading the avalanche forecast and giving it some thought.