BBC monthly outlook
Summary
Changeable conditions. Colder interludes
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Saturday 28 November – Sunday 6 December
Calm and mainly dry at first, then more unsettled.
High pressure will be extensive over the UK this weekend, bringing gentle winds. A weak warm front progressing north across south-west England, the Midlands and Wales on Saturday 28th November will bring extensive cloud cover, mist, hill fog and some light rain and drizzle. Any lingering light rain on Saturday morning over northern and western Scotland will clear. Best of any sunshine will be over northern Scotland and the far south-east of England in the early afternoon. Most places dry on Sunday 29th, but sunny intervals will be limited, and it will be quite misty and murky.
Not as frosty in southern areas this weekend, as earlier this week. Early next week, a cold front will move south-eastwards, bringing a short spell of wet and breezy weather.
A cold end to Monday night with a local frost in northern parts by dawn. Central and southern areas will have a cold evening and night on Tuesday night, with frost and patchy fog. A more unsettled second half of next week, as low pressure deepens to the north-west of the UK and then tracks right overhead. At this stage, there is some uncertainty on the strength of the winds over southern areas on Wednesday night and Thursday. But there is good agreement that rain and then scattered showers will affect all parts.
Cold enough for some snow over the hills and mountains in the north and west by Friday. A rather cold and showery end to the week.
Monday 7 December – Sunday 13 December
Wettest and windiest in the south. Rather cold.
High pressure will often be positioned to the west of the UK, out over the north Atlantic, during this week. And there is also a strong signal for areas of low pressure to become slow moving over Spain, southern France, Italy and the Alps. This will bring plenty of cloud, wind, rainfall and mountain snow here. For the UK, it seems that at least a couple of low pressure areas will push south-eastwards during the week. But with some calmer, drier, brighter weather in between them. Back in November, we experienced long periods of very mild weather.
This was due to high pressure over the near continent and a sustained south-westerly flow of balmy air from the sub-tropical Atlantic. There was little in the way of cold air from the north. Mid-December promises to be different, as we should see the winds coming in from the north and north-west more regularly. Frosts will be more frequent and we are likely to see some wintry showers, perhaps even some heavy snow showers over the higher ground in the north. Low pressure areas tracking to the south of the UK mean that western Scotland and Cumbria tend to see less rainfall than average, with the wettest weather over southern England instead. The frequency of strong wind events and westerly gales will be lower than a typical December in Scotland. But southern areas will have the best chance of seeing a few very windy days.
Monday 14 December – Sunday 27 December
Variable temperatures. Wet weather shifting north.
The middle of December will continue to see a strong ridge of high pressure over the north Atlantic. This will steer areas of low pressure south-east across the UK, France and then down into southern Europe. Spells of rain and brisk winds, especially over southern parts of the UK. It should be cold enough for some of the rain to fall as sleet and snow, especially over higher elevations, but not exclusively so. Some heavy wet snow falling to low levels cannot be completely excluded - we've seen it before in recent Decembers with a similar weather pattern, such as 2011 and especially 2017.
Once the low pressure areas track away to the south of the UK, there will tend to be two or three days with gentle winds, sunnier skies but also some cold air, with overnight frost. Patchy freezing fog is also possible when high pressure builds over the UK more intensely and we get some calm, clear nights. The Christmas week is now in the forecast range for the first time! It's too early to make a prediction of what the weather will be like over the UK on Christmas Day itself, but we can look at what the latest forecast guidance is suggesting for the week as whole. A consensus of the latest predictions suggest that high pressure will start to build over France, Germany and southern England.
Meanwhile, low pressure track starts to shift further north than earlier in December. This would suggest a trend to less cold weather, as winds over the UK come in from the south-west more often. North-western have the greatest chance of wet and windy weather, while the southern and eastern half of the UK will become drier and more settled, but with some mist and fog.
Further ahead
Now we have the festive holiday period within the month-ahead range, our subsequent updates will attempt to fine tune the details for the second half of December. We'll be keeping a close eye on the charts for any possibility of a white Christmas!
https://www.bbc.co.uk/weather/outlook