The Coldest Day of the Winter so Far.
9th February 2021
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As I am sure everybody has noticed we are under the influence of some very cold air at the moment. Last night was the coldest of the winter so far. However,Â with winds easing temperatures might drop even further tonight. It was certainty a cold day on the hill with a strong breeze and a midday summit temperature, as measured by the met office tower at 1130m, of -10.2Â°C. I had a look back the the snowpit records since 2008, and that is the lowest midday temperature summit temperature we have recorded here in Lochaber. The previous low was -9.0Â°C in December 2010.
The base of the snowpack is almost always at 0Â°C, and so these low temperature tend to create strong temperature gradients in the snowpack, which in turn can lead to the formation of weak crystals such as facets and depth hoar. I saw evidence of facets today below an old crust.
Due to the variability in snowpack depth and other variable, these types of crystal can be quite spatially variable in their formation. This can (and does) lead to weaknesses in some areas but not others. So in the current conditions don’t be fooled into thinking that just because not much seems to be changing on the surface of the snowpack, that nothing is going within the snowpack.
A tweet from the Met Office, last night was the coldest night of the winter so far. I read elsewhere that it was the coldest night since 2012 (when a temperature of -18.3 degree Celcius was recorded in Buckinghamshire).
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