British Summer Time
25th March 2018
(Above) British Summer Time started today. Cue: snowfall, drifting for most of the day above 850m and 3 cornice triggered, but minor, dry slab avalanches.
(Above) En route to Coire Chriochairein. Visibility was pretty good between the showers and the sun came out intermittently. Old wet and quite deep snow below 750m which made for slow progress. Big contrast up near the plateau where winter clearly hadn’t been told that BST had been declared overnight.
(Above)Â Plumes of spindrift coming off the rim of Coire nan Gamhna. The lowest point of the coire rim is at 970m and snow is being carried away from the camera. W winds overnight turned more WNW during the day and carried a fair amount of spindrift. This was deposited as windslab high on lee slope coire rims and at gully heads where instability tended to be localised.
(Above) Looking across to Bellevue Buttress centre with the top of Raeburn’s Gully on the right.
(Above) Detailed shot of Bellevue Buttress. This is a very steep and cold ENE aspect, with the cornice line at around 1060m. Note the ‘cones’ of loose snow at the base of the crags. This sluffed off earlier in the morning before the wind shifted to WNW. An interesting counterpoint to this was roller ball activity sparked off by the sun on steep S and SE aspects on the other side of the mountain.
(Above) Coire Chriochairein. E and ESE aspects between 1000 and 960m. Three minor cornice triggered dry slab avalanches here around midday. Left, right and centre of shot. New cornices tended to be relatively small but very fragile. Instability localised here above 950m with better stability at lower altitudes in most places as well as in all scoured locations.
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Brendan
25th March 2018 8:43 pm
Some pretty substantial avalanches running down the north facing slopes of the Inner Coire today (near to The Window), one of which big enough to move a car. We camped in Coire Ardair last night, (Saturday) and heard rumbles through the night……
Good firm snowpack leading up to The Window (we stuck closely to north side) with a few patches of fresh windslab near the top, as described in the updated avalanche report.
Keep up the good work!
Brendan
meagaidhadmin
25th March 2018 9:12 pm
Thanks for the info, Brendan.
We had quite a lot more snow than forecast – much the same problem over on the Ben, too.
I’m surmising that the debris you saw was below ‘Cinderella'(?), which most definitely has a ‘bit of previous’ and is one of our most frequent repeat offenders! Very large cornices can grow around the rim of the amphitheatre which forms the last part of the ‘Cinderella’. When this collapses it quite often cleans out the whole gully and debris from it has been known, on occasion, to run right across the floor of the Inner Coire to meet the south-facing crags on the other side.
A not very auspicious start to ‘summer’!
brendan
26th March 2018 11:43 am
Not sure of name of gully (I’m a ‘walker’ not a climber) but it was the most obvious gully on south side of the climb up to the window, about 100m below the col. I reckon it ran half way across the slopes below The Window. Some big blocks too.
Thanks to your excellent forecasts and blogs we were well across to the north side with a grandstand view, rather than buried under a pile of snow….
Given the obvious recent slides it was a bit of a surprise to see several teams out climbing yesterday.
Brendan
meagaidhadmin
26th March 2018 11:05 pm
If there were big blocks then a substantial portion of the debris was probably cornice.
Just to complicate matters, there had been a fair number of wet/moist cornice collapses a day or so before late Sat/early Sunday. If the blocky debris you saw was wet/moist snow it would almost certainly pre-dates late Saturday/early Sunday’s poor stability – see the one of the blog photos for 24th March. Had the debris been very angular and sort of dry & chalky then it probably fell down shortly before you spotted the remains of the slide on Sunday.
Dating debris can be tricky since snow texture changes rapidly above 0 degrees C.
Edit: 28/3/18. Had a close look today. Definitely very old debris – probably from or before 24th March.