Developments later on Boxing Day and into holiday Saturday have been causing us a bit of a headache for a few days now. Yes, there has been a consistent signal for a significant low pressure centre to develop close to the UK and impact upon the nation during that period but the track and intensity of the system have been impossible to pin down as successive computer model runs produced new scenarios. The next 24 hours should see a clearer picture emerging but there is still much to play for in terms of the track of the low and the resulting weather and potential impacts emanating from it.
Given the impending Christmas break it was important to have some form of alert out today but invariably in such an uncertain situation you will need to keep abreast of changes in the forecast and associated impacts through Christmas and into Boxing Day.
The most probable scenario at this stage is for the aforementioned low to track across the UK, its intensifying centre passing close to the England/Scotland border come midnight Friday/Saturday. The exact track is important as the associated precipitation immediately to the north of the centre will be falling into what will be cold air, cold enough for snow to reach the ground and perhaps accumulate, especially at higher levels. Further south any snow should be more transient and more likely to revert to rain. With a deepening low crossing the country no surprises for guessing that wind will feature in the forecast although to what degree remains uncertain, the coastal fringes being at greatest risk from any disruptive winds.
To capture all of this the Met Office have issued a yellow alert for both snow and wind (risk level currently a low likelihood of significant impacts), valid from 1500 Friday to 1500 Saturday and covering almost all of Cumbria as well as the far north of Lancashire. Please see the full version of the warning on the Met Office website. I should add that the far north of Cumbria is also included in a yellow warning for ice tonight as scattered evening showers are followed by clearer skies with a consequent risk of ice forming on untreated surfaces. Again see the usual sources for the full version of the warning.
Once the Friday/Saturday event is through we look to be entering a quieter phase in the weather as high pressure builds in from the west to give a more settled (though likely chilly) feel to the closing days of 2014.
This will be my final briefing to you for 2014 but I dare say you’ll be hearing updates from my team colleagues as the week progresses. In the meantime I wish you all (again) a very happy Christmas and New Year,
With kind regards,
Alan Goodman; Met Office Advisor (Civil Contingencies)