Lights are on but nobody’s at home.
17th March 2020
Empty car park and SNH personnel notable by their absence at Aberarder – although there was some abandoned machinery so maybe they were on a tea break – so all but deserted at Creag Meagaidh today.
Bright start augured well but, as is often the case, the sucker punch came later!
(Above) Sunlit pastoral idyll this morning. Looking west from the A86 towards (L to R) Creag Mhor, Puist Coire Ardair, Sron a Ghoire and part of the Post Face. Good snow cover though a bit wasted at lower altitudes, circa 500m.
(Above) Wall Gully – highlighted. A safe and high snow sampling site on the Eastern edge of Coire Chriochairein was today’s venue. Looks good in the sun, doesn’t it? We like this location because it’s high (900m+) and a good analogue for the Post Face and other similar aspects. It doesn’t have a big fetch but nevertheless provides relevant and useful snowpack data for us. (Uinneag Coire a Chaorainn aka Sharks Fin Gully is even better, being higher and with quite a long fetch. See below.) You can just see the line of the old wall descending down from the gully towards the main Coire Ardair path.
Wall Gully is highlighted in dark orange. Fetch is an important component of the avalanche recipe here at Creag Meagaidh because the gently undulating snow-holding ground above 900m acts as a drifting ‘multiplier’. Snow falling on this high ground is very often stripped from the plateau and redeposited as windslab on to any steep lee areas. Windslab build up can be very fast, even without snowfall, due to the enormous buffer stock of snow which is often present in this high, rolling terrain. Since our prevailing winds come from somewhere between SW and W, N to E aspects get fully loaded with snow quickly. But only when the snow is cold enough, of the right texture and the wind strong enough to make this happen. As you can see, Shark’s Fin Gully (SFG) has over 1km of fetch of snow-holding ground over 900m – arrowed. Wall Gully has a very limited high level fetch – the ground falls away quite sharply to the west of it. No surprise then that SFG has great potential for digging huge, capacious snow holes whilst Wall Gully doesn’t.
(Above) Significant avalanche activity today, here in Coire Chriochairein. One of the biggest avalanches I’ve seen in this coire. I estimated it to be a Size 2.5, but maybe even a Size 3. 100m crownwall, running out 200m. Definitely cornice triggered – you can see where the cornice fell from – and slid some time this morning. Had been very mild and wet at all levels overnight and early in the day which probably initiated the cornice collapse.
(Above) A better view of the crownwall and start zone of the avalanche above The Pipes. There was another avalanche (Size 1) from the opening pitch of Staghorn Gully but I only managed to glimpse it later just as the weather started to deteriorate.
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