BBC monthly outlook
Summary
Often unsettled with increasing risk of cold
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Wednesday 13 January – Sunday 17 January
Variable temperatures but less cold than recently
The rest of the working week is expected to see some quite changeable weather across the UK, with a low pressure system on Wednesday and Thursday bringing some widespread rain and cloudy skies. For Northern Ireland, rain will be heavy and last for much of the day, bringing a risk of some local flooding. Scotland and Northern England will see a risk of snow or ice for higher ground. From Thursday and into Friday, a ridge of high pressure will extend into the UK from the south and southwest, bringing a respite from the wet weather and also keeping temperatures hovering near normal.
However, the next low pressure system will begin to push in from the west, reaching Northern Ireland and western Scotland overnight Friday into the weekend, so not everyone will be dry. This low will make for an unsettled weekend with some milder but wetter weather for Saturday followed by a drier, colder and windier Sunday. There will be a split in temperatures with northern areas a bit colder than normal on Sunday while the southern half of the country is near or a little above normal, but cloudier. In short, we expect a volatile week of temperature swings and frequent rain, along with a chance of some snow for northern areas.
Monday 18 January – Sunday 24 January
Wetter weather with some cold snaps
As we enter late-January, the forecast gets more complicated. There are some strong signals for the low pressure track (which at the moment is displaced south in Spain and Italy) to return nearer to the UK, which would bring milder but wetter and windier weather. However, this comes with a rather large caveat: the polar vortex. This is a circulation of winds in the stratosphere, about 40-60 kilometres above the surface, and typically keeps cold Arctic air trapped at the pole. In early January, the vortex weakened and became displaced over Europe, and it's still overhead now. It usually takes a few weeks for the effects to reach the surface, so around mid-to-late January until early February we expect an increased chance of cold outbreaks.
It continues to look like the coldest weather will miss us to the east, staying mostly in Scandinavia, Eastern Europe, and western Russia. There is still uncertainty on the westward extent of the cold air, and we could see a few cold blasts mixed in with some milder, wetter spells. These will be felt most in eastern and northern parts of the UK, while southern and western areas more often slightly milder. A highly variable forecast with large swings in temperature along with some wet and windy days is still expected, continuing from mid-January. Confidence is medium to low on the forecast, mainly due to the uncertainty in the temperatures. The UK is on a fine line between being more frequently cold or more frequently mild. There is greater risk of more widespread cold, as we have seen in previous years with a displaced polar vortex.
Thursday 25 February – Sunday 7 February
Unsettled with cold outbreaks nearby
Towards the end of January and into early February, there continues to be strong signals for a return of low pressure tracking from the south bringing wetter, windier, and milder conditions. However, a second weakening of the polar vortex is beginning in Siberia now, and this will likely delay the milder air from reaching us, prolonging the risk of cold. As the polar vortex returns to the Arctic and strengthens again by early February, we should begin to see the cold become less widespread, but this may be delayed for north Europe until nearer to mid-February. As with the previous week, we expect the cold to mostly stay to the east of us and low pressure to be the dominant feature, especially into February.
The UK will tend to find itself on the boundary between the cold high pressure to the east and the milder low pressure to the west, so confidence is pretty low on the specifics. A minor shift in the weather pattern will lead to some large changes in the expected conditions for the UK, so some caution is needed at this range. In general, it will likely be on the colder side of average mixed with some mild, wetter spells that last for 2-3 days at a time. Between low pressure systems there will be some sharp cold snaps, with a chance that cold could well turn more widespread if the polar vortex lingers in Russia longer than expected.
Further ahead
As a second polar vortex weakening event is ongoing, we will be able to look deeper into February next time to examine when the cold outbreak may end.
https://www.bbc.co.uk/weather/outlook
Mid January was always forecast to be milder and they are right as are the met and models. But the BBC has mentioned just about every possible outcome /scenario for the UK. Just shows the lack of confidence in the long range forecasts esp if we have a 2nd SSW. It could be a long and frustrating few weeks of model watching esp knowing many other parts of Europe are in a mid winter freeze. Moscow is expecting a daytime high of -20c on Saturday and Sunday with lows down to -24c. Been a few years since they have seen such low daytime maxes in January! Anyone else in for a roller coaster ride!?