BBC monthly outlook
Summary
Highly variable temperatures for a few weeks.
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Saturday 16 January – Sunday 24 January
Swingy temperatures and snow risks for some.
As a cold ridge of high pressure over the UK slides away to the southeast into Europe this weekend, a frontal system will push in from the Atlantic. This front will bring in some milder air. It will also bring snow and ice for northern and eastern areas on Saturday morning, with the milder air arriving slightly later. Sunday and Monday will see another ridge of high pressure slide over the southern half of the UK. Things will stay rather breezy and unsettled for the north. This high will bring in plenty of cloud though, so it won't tend to be too sunny. Next week, a stronger low pressure system is expected to move in on Monday bringing some wet weather throughout the country through midweek.
Snow is unlikely expected for the highest ground in Scotland, thanks to the milder sub-tropical air moving in from the Atlantic. Temperatures will be above average through midweek, but it is still January, so highs will still tend to be below 10C for most. For the second half of the week and weekend, the temperatures will dip away below average again, with a risk of some snow showers for northern parts of Scotland and perhaps into Northeast England. The low pressure from Monday will likely stall over Central Europe as high pressure builds in Greenland and Russia. This will keep a cold northerly wind over the UK for a few days, but it will also be a bit drier for southern areas. Next weekend, there is potential for a low to bring some wintry weather for southern England as it speeds through the English Channel. But confidence is low on whether this will materialise or not.
Monday 25 January – Sunday 31 January
Turning wetter and milder with some cold snaps.
For the rest of January, the high pressure system building in Greenland will play a major role in our weather pattern, despite being hundreds of miles away. This is because the jet stream, a ribbon of fast moving air in the upper atmosphere that drives weather systems, is being pushed further south in the Atlantic. The southward track of low pressure systems will allow them to pick up some milder sub-tropical air and drag it into western Europe behind warm fronts. This weather pattern is likely to persist through the week, so we will see low pressure systems bring milder air from the west and southwest along with plenty of rain and some stronger winds.
Between these lows there will be a few days of some sharp cold and dry weather as a brisk northerly wind develops. As the next fronts move in over the colder air, there will be risks of some wintry weather for some areas, mainly the north but also the east too. Snow or freezing rain is possible, even to low levels at times. So, while a repeat of 2018's Beast of the East does not appear likely, that doesn't mean we will escape any potentially disruptive wintry weather. If high pressure in Russia is a bit stronger than we currently expect, lows will tend to stall in Central Europe or Scandinavia. This will bring some longer-lived cold snaps to the UK. This is more of a risk scenario though, with a thirty percent chance of happening.
Monday 1 February – Sunday 14 February
Staying unsettled and increasingly milder.
By early February, the high pressure system in Greenland is expected to begin to ease, but it will certainty take its time doing it. As it slowly weakens, lows will be able to move into Northwest Europe more freely, bringing some longer-lived mild spells associated with warm fronts. Between the low pressure systems, cold snaps are still likely, but will become increasingly shorter-lived. The temperature is likely to still be very changeable, shifting from a few degrees above average in the mild spells to several degrees below average in the cold snaps with some sharp frosts likely. Again, as with late January, some wintry weather is possible as fronts move in over the top of the colder air.
There are some signals that by mid-February it may tend to be milder most of the time which will ease the risk for wintry weather (at least for everywhere but the Scottish Highlands!). However, confidence is low at this range as computer model forecast skill as been very poor in recent days. There is a high risk for more prolonged cold to develop into mid-February, which would be caused by stronger high pressure to the north. This would also be a drier pattern for the UK as the Atlantic low pressure systems mainly track south of us and head into France, Spain, and Portugal.
Further ahead
Hopefully, we will be able to better pin down the weather pattern for February with some additional data on the high pressure system in Greenland.
https://www.bbc.co.uk/weather/outlook