Uinneag Coire a Chaorainn
30th January 2017
(Above) Good clear view of the Post Face from the path. The exit ramps of the 3 principal gullies in the photo have a covering of soft, weak windslab. There’s not a huge amount of snow there but what there is is underlain by a weak layer. Instability here and in similar locations tends to be localised. Some erosion of snow noted later on this East aspect as the SE winds strengthened.
(Above) Detailed shot of Coire a Chriochairein – a very steep East aspect at around 1000m. Crownwall from a Size 1 cornice-triggered avalanche circled. Estimate this released later in the day yesterday – Sunday. Approx dimensions: 15m wide crownwall, 20-25cm deep and running out 70m. Little wisps of spindrift just visible on the skyline indicating snow is being eroded nearby.
Wind speeds and scouring/drifting increased as the day progressed:-
(Above) The entrance to Uinneag Coire a Chaorainn 910m (Shark’s Fin Gully). A photo of the immediate lee area on the Carn Liath plateau about 20m away from where the video clip was shot. The drifted snow was not particularly deep or extensive this afternoon but certainly was increasing…………
(Above) …….enough for a small Size 1 avalanche to trigger really easily on a very steep NE aspect within this high re-entrant. Approx size 10-15m across the crownwall and max 20cm deep, though, as you can see, it does vary a bit on each flank of the crownwall. (This is the site of last winter’s remarkably well-constructed military snow holes which featured on our blog.)
It’s a classic little terrain trap. Of minor consequence today but with a bigger build up the potential for complete burial would increase dramatically. The video clip below gives a better idea of the terrain layout:-
(Above) 30m shooting cracks (look carefully!) on this moderately angled NW aspect at 920m Â just around the corner from Shark’s Fin Gully. (The photo needed a lot of ‘post-production’ work to get enough contrast for the the slope failure crack to show. Apologies for the slightly pink and blue tinge).Â The crack propagated across the slope instantaneously when I approached from the above. Again, of no great consequence at the time since the bulge of windslab was only 30cm deep and extended 10-15m up and down the slope, but signs like this are indicative of very poor stability. It’s ‘bulls-eye’ information for slopes of similar angle and aspect.
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