A wet thaw.

29th January 2023

Another temperature cycle today, with the double whammy of a lot of rain to the summits. So, some further snow loss at lower elevations. In fact, wetter than an otters pocket is the phrase that springs to mind for today.

The remaining snowpack will re-freeze tonight as the temperatures drop. There will also be some snow showers on very strong westerly winds but the amounts are not expected to be significant. See the main avalanche report for details.

Colder conditions forecast for mid week.

Ben Nevis is up there somewhere.

You know its not a summit day when the CIC crag waterfalls are flowing upwards!

Looking up to the base of the minus face, past the bottom of the Douglas Boulder.

The inevitable water cycle. Hopefully it will return to us as snow at a later date.

Visibility on Aonach Mor was perhaps slightly better than on the Ben, but otherwise conditions were pretty similar.  

Being almost the end of January, and a good month and a half since avalanche forecasting started for the season in Lochaber, I thought it might be a good time to have a look at some weather data for the season so far. I think a general description would be pretty average really.

A graph of the summit temperatures so for this winter. A couple of milder spells, and couple of colder spells, but generally pretty average really (the average, max and min values are the based on data from 2008-2022). 

Nothing particularly significant about the temperature anomaly (again the base period is 2008-2022 for not more a scientific reason than this is the dataset I have access to).

Making some assumptions about midday summit temperatures tomorrow and Tuesday gives a January average for 2023 of -1.5 degrees C. Of the past 16 years this is the 12th coldest, or 4th warmest depending on what way you want to look at it. The warmest January was 2020 at -0.2 degrees C, the coldest 2010 at -4.2 degrees C.

The cumulative no settled index for January of the past few years (making a couple of assumptions about how much snow is going to fall the next couple of days). The values in themselves probably don’t mean much (they don’t correspond to cm’s or anything like that), but are probably a reasonable way to compare how much snow fell in January of each year. This year is about average (this year it will be about 90, the average of the previous 15 years is 91). 2014 was the snowiest with 208, 2022 the least snowy with 36. 

Comments on this post

  • Adam Kassyk
    29th January 2023 8:54 pm

    Hi, interesting data, even if the conclusions aren’t terribly encouraging. I’m puzzled by the snow data though. I recall 2010, 2011 and 2021 were big snow winters, but that’s not reflected in these figures. Am I missing something, or is my memory playing tricks?

    • lochaberadmin
      30th January 2023 6:28 pm

      So there is a difference between how much snow falls, and how snowy it feels, and that difference (or lack of) depends on how much it thaws. So as one of the graphs above shows January 2010 and 2021 were very cold (2011 was not so cold but the month before December 2010 was).They were also relatively dry months in terms of precipitation (the data can be found here https://www.metoffice.gov.uk/research/climate/maps-and-data/uk-actual-and-anomaly-maps). However, the fact that the snow did not thaw meant although snowfall/precipitation in general was low, so was melting. A thaw (and rain especially) will cause the snowpack to melt and to what survives to become denser. Therefor without thawing a relatively small amount of snow feels like a lot especially as the hills look white. With various heavy thaw a lot of snow can feel like not much due to melt, densification and exposed areas looking black. Think how snowy would this winter be/feel if it had not thawed even although the amount of snow that feel would be the same.

  • Scott Whitehead
    29th January 2023 11:32 pm

    Thanks for this – these stats are really helpful.

    • lochaberadmin
      30th January 2023 6:29 pm

      Glad you like the stats, I always enjoy a good weather/snow graph!

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