Fat Tuesday: avalanche day.
13th February 2018
(Above) Overcast this morning after a sustained bout of snowfall. Aberarder Farmhouse – looking across to Binnean Shuas. Note traces of drifting up high.
(Above) Looking into a distant Coire Chriochairein from Aberarder just as the sun starts to appear. More avalanche activity in this coire today – probably cornice triggered.
(Above) A ski tour into Coire Chrannaig today to check out some low altitude avalanche debris. A view across the Coire Chrannaig birches towards a completely white Sron a Ghoire. Great cover at the moment. New snow at all levels and just enough allow skiing to and from the farmhouse.
(Above) The tree line in Coire Chrannaig. More or less continuous cover. Deep drifts in all lee areas. Top of centre skyline is one of the minor peaks of Na Cnapanan at 625m.
(Above) One of the rare perks of our job (but only a perk if you’re not breaking trial. Doh!).
(Above) Eye-balled this debris from the road driving to “work”. Never seen avalanche debris within Coire Chrannaig, the broad and long angled coire which rises up to the summit of Carn Liath. The crownwall above is at a little over 600m, which is very low. Some sunshine encouraged a little early consolidation in the snow here later but instability remained more profound at higher altitudes in many locations.
(Above) Up close & personal. Interesting new snow natural avalanche which slid a couple of hours prior to our visit, during the period of snowing and blowing. Part of our formal observations today was a fracture line profile at this site – details on the SAIS ‘Meggie web page. Size 1 avalanche but enough to knock you over, partially bury you and have you wondering about the purity of your underwear. Debris about 1m deep. There was another Size 1 in the coire a little further east of this one.
(Above) The SE slopes of Na Cnapanan, here at around 550m. A few more Size 1 avalanches and less than 1km away from Coire Chrannaig. Early morning events we think.
(Above) The approach slopes to the summit of Sron a Ghoire, showing large scale wind rippling effect on the surface and slab build up. Was pretty windy overnight – mainly South Easterly but more Westerly with morning snowfall. (Wind had been blowing left to right in the photo above).
(Above) Looking back to Sron a Ghoire and the Creag Meagaidh massif from Kinloch Laggan this afternoon. A white and snowy prospect.
More wind & snow in the forecast. Again.
(Contemporary secular society yadda, yadda, yadda…So just in case you’re wondering. Fat Tuesday > Mardi Gras > Shrove Tuesday)
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13th February 2018 10:28 pm
Thanks again for an excellent blog, with great photos!
Could you educate the remedial mountain folk out there (I include myself in this bunch) and explain how you guestimate the time an avalanche slides? Are there any telltale signs to look out for?
13th February 2018 11:07 pm
It’s science. We use an algorithm involving this:-
(The above solution requires the eating of donuts. Obviously.)
Hopefully, a Cambridge-educated scientist will chip in and verify our approach.
I hope this answers your question.
Seriously now. Avalanche debris is pretty easy to date if you look at snow & avalanches a lot and you know in some detail what the weather has been doing in your area.
I was forecasting on Monday and, as always, had a good general look round to see if there was evidence of avalanche activity – debris, crownwalls etc. I hadn’t seen any at all in Coire Chrannaig on Monday so seeing debris et al on Tuesday morning meant the the avalanches there were no older than 18hrs. So that’s the baseline time when evaluating the age of this avalanche.
We also knew from the previous day’s Met Office forecast that the snow showers and wind would ease considerably no later than 9-10am, which is the way it turned out to be on Tuesday. Therefore beyond that time stability would not continue to decline. If anything – given the prevailing weather & snowpack – it would begin to improve slowly at that particular altitude, which is the way it turned out.
When we got to the avalanche site we could see a very clean slidepath and crownwall almost completely devoid of new drifted snow. In addition, the crownwall & debris had clean, sharp, well-defined edges/surfaces even though it was composed of really quite soft snow. There had been no/negligible age hardening (equitemperature metamorphosis) of the debris – it felt soft and very fresh. A good deal of experience is required to do this, together with detailed knowledge from the day before.
In brief, it’s a sort of mental triangulation of timings (weather etc), simple observations, and interpreting snow metamorphosis when you’re on scene at the avalanche. In this case we were pretty confident the avalanche had occurred no later than about 9am, which is when it stopped blowing & snowing at ‘Meggie.
13th February 2018 10:32 pm
On this Fat Tuesday my wife made me three wonderful pancakes with real lemon juice and sugar. I will cycle 30miles tomorrow to work them off!
And……..re your photos and reports and the present conditions……..four of us once stood transfixed in the Hidden Valley of Stolen Cows in Glencoe while slab avalanches thundered in front and behind us from the northern slopes. I particularly and distinctly remember that none of us spoke but I remember looking into the eyes of the others as we silently turned and quietly retreated. Nothing was said as we all knew just how close it had been.
I always remember the deaths of the lads from Northern Ireland who were killed in an avalanche from the Castle as they walked in to the CIC hut on the Ben. You would never have thought that to be a dangerous position.