Report 2 3/12/10
In the depths of winter – already
Hi All,
As no doubt you’re well aware the E. of Scotland has received heavy snowfall in the last week. In Boat of Garten, we must have received around 16” (40cm) in total over last weekend and at the beginning of the week. This depth has decreased with the snow falling on relatively warm ground. Bearing in mind that often the lowest valley temperatures of the season correlate with high pressure and the longest nights (i.e. Dec & Jan), the – 10’s we’ve been having are not totally exceptional for this area at this time of year. What has been exceptional is the persistence of the cold temperatures for this time as well as the -20 last night! Once the main fall had stopped the temperature didn’t rise above -5 deg C. As you would expect with the high pressure around there has been some strong temperature inversions with the ambient hill temperature being warmer.
On the mountains there are some very deep drifts along with a high avalanche risk. A number of people have already been caught out this season – a common misconception being that’s “it’s too early for avalanches”. With the amount of drifting and the huge catchment area that is the Cairngorm Plateau, an inch fall can translate as many inches in sheltered lee’s i.e. coire headwalls. This, combined with something as minor as a temporary lull in the wind speed can be enough to create a weak layer within the snowpack. Many of you may have already seen the U-tube video of the Coire Cais Headwall being set off the other week. With the calm and very cold night time temperatures hoar frost crystals (surface facets in avalanche jargon) can be expected (possibly depth hoar frost crystals also) – again potentially another weak layer should they become buried.
The snow is consolidating on the mountains , all-be-it relatively slowly compared to the effects of a freeze thaw cycle. The drifting helps this by breaking up snowflakes and laying the crystals down in a dense layer (i.e. wind-slab) whereby their close proximity to each other allows greater bonding. There is deep cover everywhere.
It’s a very good start to the season but dare I say it “lets hope it warms up a bit”! That’s all for now.
Safe climbing
Andy
