Snow Redistribution…
11th February 2025
It is fair to say that today’s conditions made for challenging observations and photography. Visibility was poor with plenty of blowing snow further augmenting the dreich monochrome experience.
There was probably more snowfall than was forecast overnight, although it is difficult to truly estimate the quantity. What we can observe is that there is plenty of snow being transported in the wind and deposited as windslab, in steep locations or in small drifts elsewhere. This is common in winds of a South-Easterly direction. There is a large expanse of plateau to the south-east of Coire an Lochain and Coire an t-Sneachda, which provides an ample reservoir of snow to develop windslab when deposited in sheltered locations. The term “fetch”is often used by Avalanche Forecasters of a nautical persuasion meaning the distance travelled by winds, or more usually waves, across open water.
Unsurprisingly there are some new deposits of windslab around the coire rim and in gully tops, mostly of a South-West through West to North aspect above 900 metres. Although these share common characteristics in terms of location, and do not appear to be widespread, they do contain weaknesses. These deposits combined with the development of fragile cornices, result in an Avalanche Hazard of Moderate for tomorrow.
Point 1141 – this cairn at the top of the Fiacaill a’Choire Chais has been the savour of many when it appears out of the gloom. Particularly after a testing series of navigation legs at night. There aren’t many Winter Mountain Leaders, Mountaineering Instructors or Mountain Guides who haven’t been pleased to see this feature.
An isolated accumulation of new snow in Coire an t-Sneachda. At around 950 metres the regular blog visitor might notice that the wind has been blowing from right to left. In this case that is actually West to East. The prevailing wind direction has been East-South-East but yet snow accumulation appears to be in exactly the opposite aspects that would be expected. Although cross-loading is frequently mentioned in the forecast, this is an example of “reverse” loading due down draughting air creating a rotor at the coire floor. This is quite common in Coire an t-Sneachda, which is quite a windy coire…
Looking up towards ‘The Mess of Pottage’ (left), ‘Jacobs Ladder’ (centre) and the broken crags of ‘Forty Thieves’ to the right.
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Alexis Perry
11th February 2025 7:29 pm
That cornice collapse in Lochain was 8:30am; debris rolled past us as we were gearing up. Made us jump, as we were already twitchy after a hefty rockfall had trundled down about 10 minutes earlier.
ncairngormsadmin
12th February 2025 7:21 am
Thanks Alexis for letting us know. Will make sure the time is recorded.