Whatever winter sport is your passion, getting the most out of the UK winter season is inevitably about being opportunistic. You need to jump to it when the conditions are right. Getting into the hills requires some degree of planning. You need to learn all the tips you can on about how to forecast snow. When forecasters tend only to predict 3 days in advance, it doesn’t give much time to get organised.
Season passes have been released by Cairngorm Mountain and quite possibly the other ski centres across Scotland. Now’s the time to keep your eye out for the snow predictions.
This changes though when you understand atmospheric thickness and how it relates to the 5 day synoptic weather charts. Have you ever noticed those numbered dashed lines hiding behind the isobars? (see below – on Bracknell charts predicting 36 hrs or more ahead) Well they represent the thickness of the atmosphere and this directly relates to the temperature of the air-mass. Bear with me, here’s the techie bit.
Air pressure at sea level tends to equalise at around 1000mb. The colder the air, the greater the density and hence you need less of it volume wise to create that 1000mb pressure. Therefore the atmosphere is thinner at the poles than it is at the equator. Meteorologists have realised that by measuring the altitude at which the air pressure halves (i.e. is 500mb) they can plot the movement of cold air from the polar regions towards the equator. In the northern hemisphere these thickness lines represent the southern limit of cold air moving down from the north.
As far as wintry weather in the UK’s mountains is concerned it’s the 528 line (equates to 5280m) you want to watch out for. When it crosses the UK you can expect snow on the hills at least. They are a bit like contour lines. The closer together they are the more the marked the temperature change but if, lets say, the 528 line is 300 miles out to the west over the Atlantic you might be at least be expecting snow on the highest tops in Scotland. If the 510 line approaches the UK wrap up warm, very warm! The charts predicting the arrival of the “Beast from the East” had the whole of the UK enveloped beneath the 510 line!
For those of you who can jump to it and might be in need of accommodation in the Northern Cairngorms area check out Fraoch Lodge.
So you’re planning a high overnight camp and you’re wondering how warm your winter sleeping bag should be?
Likely Ambient Temperature
With a number of recent TV documentaries ‘laying it on a bit thick’ about how low the temperature can drop in Scotland’s Cairngorm Mountains you might be forgiven for thinking you were heading for somewhere akin to the high Arctic! Indeed the temperature in the Scottish Highlands has been recorded approaching -30 deg C (-27.2 to be precise – the official British record) but this has only been on three occasions in 120 years!
Interestingly, Cairngorm summit (1245m) has only ever managed a record minimum of around half of this at – 16.5 deg C (12th Jan 1987) whilst the residents of nearby Nethybridge (210m) at the foot of the mountain claimed the mercury dropped to -31.3 deg C on 10thJanuary 1982, the same night as one of the -27.2’s was recorded. Satellite evidence suggests they were right!
The vital bit of missing information on these – 30ish lows are that they’ve all been recorded as a result of temperature inversions. That is, cold air has flowed off the mountains and pooled in the valley bottoms where it’s cooled further whilst the mountain summits have remained appreciably warmer. These record minima are in no way a reflection of the likely temperature you would find on our mountains, possibly not surprising considering all our mountains are never that far from a relatively warm sea.
So what would be the likely temperature at the main snow-hole sites, let’s say, in the Cairngorms at around 1100m? Well, the seasonal minimum for 900m is usually around -8 deg C which could, at a pinch, translate to -10 deg C at 1100m but far more often in winter it’s around minus 5 and above. The point is, on our mountains we don’t experience anything like the temperatures you might get in e.g.Norway.
Be guided by advice of sales staff in the shop who should have some relevant experience. Ask for shop expert if your sales person doesn’t demonstrate sufficient knowledge of the range on sale.
Most importatly – buy quality for a sleeping mat. In winter, it is most important to make sure you are insulated from the snow beneath you as you’ll lose the majority of your bodyheat this way.
It goes without saying of course you need to be checking the weather forecasts before you head out. A tented high camp in winter needs to be carefully judged. Those who have got it wrong have ended up having their tent destroyed and gear being scatted far and wide by hurricane force winds.
Andy Bateman 14/11/14
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