Avalanche pre-cursors
6th January 2010
We’re often asked how we work out stability. The answer is that we gather together what may seem like pretty low grade information during the course of the day and then ‘triangulate’ it. Snowing? Blowing? Drifting? Where’s the build up? Getting colder? Rapid warming? Raining? Can mini-avalanches be started on small test slopes that have new slab or buried weak layers? How well bonded together are the layers? Of course there’s endless technical stuff in our snow pit but stability is worked out by weighing up (triangulating) the answers to the simple questions above. We’re looking for the ‘big picture’. We nearly always get an unequivocal indication of stability from garnering this low grade info. What’s the best single indicator of stability? – avalanche activity (or recent debris), of course. This may seem obvious but you’d be amazed at the number of people who (to their cost) think that seeing an avalanche run means the period of instability is over when it may just be beginning.
The photo (above) shows a mini test site – fresh loading on a small un-threatening slope where you’re not going to get buried. If the snow shows loads of positive avalanche indicators here you can bet that it will be a lot worse on similar aspects, at higher altitudes and on steeper ground elsewhere. Never pass up the opportunity to poke and jump on the snow in these places.
Worrying ‘whumphing’ noises everywhere there was deep new slab today- as low as 400m. Plenty of other avalanche pre-cursors as well – check out the long cracks emanating from skis on quite modestly angled ground at the test site (shown in the first photo).
Desperate to do a route? Worried about the snow? This Strathspey ice route is conveniently located next to an ‘A’ road. Very rarely in condition, it’s been getting relatively little attention recently (only two cars parked beneath it on Wednesday morning.
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