Avalanche Red Flags

In the last blog we talked about the one thing we have control over: the terrain we choose to travel through. In this blog we will chat about some of the key things that we need to look out for that are “red flags” for avalanche danger. Awareness of these red flags will help us with our terrain choices. 

When we are in the mountains there are 5 red flags that tell us the avalanche danger is increasing.

Seeing a recent avalanche like this should probably tell you to go ski on a different aspect or elevation

Red Flag 1: Recent Avalanches

The greatest sign of avalanche danger is avalanches. Seems a simple concept, but a lot of people miss this red flag. If there are avalanches happening, then we will want to avoid the aspects and elevations where these avalanches are occuring. Also, if these avalanches are happening naturally be very careful about what is above you (all links back to terrain choices).

Cracking shows us the snow is ready to slide if we get on steep enough terrain

Red Flag 2: Cracking and Whoomphing

The snowpack is really good at giving us clues that it is not happy. Whoomphs and shooting cracks are collapses in a weak layer in the snowpack. It is hard to describe a whoomph… you feel one more than you hear one.  If you think you have felt one you haven’t, you just know when you have experienced one.  Whommphing feels almost like an aftershock.  These things can happen even in flat terrain and if you experience one, and the snow doesn’t slide, then you choose your terrain wisely.  However, you wouldn’t want to go into avalanche terrain if the snowpack was giving you these warnings.

Although lots of snow is fun for skiing it will also raise avalanche danger

Red Flag 3: Rapid Snowfall

The weather is constantly changing our snowpack, but the snowpack doesn’t like rapid change, so we need to watch the weather for clues of increasing danger. If it is raining on winter snow it is time to go somewhere else. If it is snowing rapidly 3cm (1”) an hour or 30cm (1ft) in 12 hours avalanche danger will be increasing rapidly. This may just be the surface snow being weak, but a large snow fall might wake up some deeper buried monsters. Choose low angle, tree runs on these days.

Blowing snow can build a slab 5-10 times faster than it can fall from the sky

Red Flag 4: Blowing snow

Wind transports snow and can load avalanche starting zones 5 – 10 times faster than snow can fall from the sky. It will also create thick, firm, dense “slabs” of snow which, when sat on softer snow, will cause a slab problem. So, be sure to watch for blowing snow at ridgelines and watch where it is settling too, as these are areas with more danger. 

Red Flag 5: Rapid rise in temperature

When temperatures start to increase above freezing the snow will start to loose strength quickly so things will start to move. This is often an issue in spring and also after fresh snow (when we can get dramatic swings in temperatures). Timing is critical when we are dealing with temperature as often early in the morning the snow will be locked up but as things heat up the snow can start to slide. Start your ski day early so you can be descending before noon on these days.

Knowing these red flags will help with your planning and terrain choices whilst in the field.  If you are seeing these flags when you are out you might want to think about heading to safer terrain. As we learned in the last blog that could mean changing aspect or elevation and going to lower angled slopes.

Ian is a Ski Patroller, Avalanche Educator and Mountain Guide who worked for the last 11 years in Colorado, USA. He recently relocated with his family to the Lake District in England so his family could experience where he grew up and get a different take on the world from the USA view. He has been travelling in snowy mountains for over 30 years and will be running 2-day avalanche education courses in Scotland through his company www.elevationmountainguides.com.