El Alamein
9th February 2023
Another burly day was experienced in the Cairngorms today, with Storm Force winds at higher elevations. The maximum gust recorded on Cairn Gorm summit was 106 mph, while the mean windspeed was 62 mph. This does explain why it was a bit of a battle over to my snow profile location.
With winds from the West the Northern Cairngorms presents an atypical picture with regard to avalanche hazard. When the mountains are viewed from Glenmore little snow is seen currently apart from the lee side of the broad ridges, snow patches and ribbons in the burn lines. However, in the coires and further into the interior there is a slightly different picture.
Following light snow showers last night, unstable windslab was deposited throughout the day on North-East to South-East aspects above 950 metres. This is generally found in steep wind sheltered locations where it overlies older firm and consolidated snow.
The distribution of windslab is variable due to the storm force winds. Where powerful down droughts exist, snow has been carried to lower elevations or has ablated into the atmosphere e.g. in Coire Cas and Coire an t-Sneachda. The deep sided valleys that run north-south through the Cairngorms (more on them in a bit) provide broad easterly facing slopes ideal for windslab accumulation.
This is the situation that prevails at the moment, with the greatest accumulations noted in Strath Nethy, and the Lairig Ghru (seen fleetingly today). Avalanche activity was noted on a North-East facing slope of around 1100 metres, this most likely triggered by cornice collapse overnight.
Windslab will continue to accumulate overnight, but there will be a slowly stabilising trend tomorrow as the freezing level rises above the summits by dawn.
Three people seen today descending the Fiacaill a’Choire Chais. Note the older firm and icy snow (grey), with overlying deposits of windslab (white). The change between these two snow types is obvious at the moment in many locations. Isolated and avoidable here, the windslab was more extensive along the east facing slopes of Strath Nethy.
The El Alamein Refuge, Coire na Spreidhe. It was a bit of a battle to get there today in the high winds, but it is best I make no comparison with the decisive WWII battle after which it is named.
Old firm and consolidated nevé (top right). New windslab (bottom left). This shot highlights the conditions at the moment. You can be on firm, consolidated and stable snow one moment, but a couple of steps and the snow pack has very different characteristics.
A shooting crack in freshly deposited windslab. This was a small drift at around 900 metres in the ski area.
The big valleys of Strath Nethy and the Lairig Ghru have always fascinated me, partially given the fact that they bisect the Cairngorm Granite pluton. The pluton is such a large chunk of granite that I have often wondered as to the structural controls on their development.
A bit of research tells me that here in the Cairngorms that the valleys align closely to quartz veins and linear alteration zones, which are some of weakness in the granite pluton. Quite unusual as the dominant control of these things would normally be joint sets in other rock types. (To be continued…)
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Simon Stokes
10th February 2023 8:42 am
Great blog entry this one
ncairngormsadmin
10th February 2023 12:26 pm
Thanks Simon, Good to know these blogs are useful beyond the images alone.