BBC monthly outlook
Summary
Unsettled conditions continuing. Short cold snaps.
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Wednesday 18 November – Sunday 22 November
A short cold spell on Thursday. Otherwise mild.
Wednesday will be another unusually mild mid-November day, with maximum temperatures climbing to 16C, perhaps even 17C in a few areas. After a dry and locally bright start over eastern England, it will be windy and unsettled again, as another low pressure area moves in. Wednesday night will see winds peak in strength across the UK, with gusts of 55-65mph over exposed western and northern areas. Even across sheltered inland parts of England, maximum gusts will get close to 40mph.
A significant change in temperature will occur during Thursday, as a colder north-westerly wind sets in. But there will also be widespread sunny spells for many of us, and only a few showers. In northern Scotland, the showers will be heavy and frequent, falling readily as sleet and snow as a cold Arctic blast arrives. Some local snow accumulations are likely, even at low levels. Widespread clear spells and winds easing on Thursday evening will lead to the coldest night since early November. Eastern areas will see a frost. A new frontal system will push cloud, rain and milder air raidly into many western and northern areas during the second half of the night. Snow for a time over the Scottish high ground before it turns milder.
The rest of the week will be mild and windy, as a deep Atlantic low pressure area returns strong westerly winds. Wettest over western Scotland, Cumbria and north-west Wales, while the south and east of the UK will have some drier weather with a few sunny intervals.
Monday 23 November – Sunday 29 November
Milder than average. Wet and windy.
A low pressure track near or overhead the UK is very likely during the final week of November, so we can all expect some more rain coupled with blustery winds. The fine detail for this particular week has been tricky to pin down over the last few days, with forecast computer models showing a lot of variability in where they expect the focus of the low pressure track to be.
The most likely outcome is that high pressure will be quite extensive over the near continent, more than we predicted in the previous update. This high pressure influence will help to steer the jet stream and its associated Atlantic low pressure areas just to the north and west of the UK on many days, with winds often blowing in from a mild south-westerly direction.
This means that cold snaps are less likely and mild weather patterns should predominate, even at night. If we do see a cold snap it will just be for one or two days and most likely over northern and eastern areas of the UK. Further bands of heavy rain and brisk south-westerly winds will feature. Gales are possible in the north during the second half of the week. North-western areas will be wetter than average, while rainfall amounts across the south and east will be closer to average, with most of the rain falling in the second half of the week.
Monday 30 November – Sunday 6 December
Westerly winds and unsettled. Brief cold snaps.
The latest forecast guidance continues to indicate that winds from a westerly direction will dominate the first half of December. This means that UK temperatures will be close to, or a little above the seasonal average for this 2 week period as whole. The prospect of a sustained and very cold weather pattern, with severe frosts and widespread lowland snowfall, as we saw in December 2010, is very unlikely.
Nevertheless, we should be wary of a couple of short-lived cold snaps, when winds swing into the north for a few days. This weather pattern most recently occurred in December 2017. There were several sharp swings in temperature during that month, from very mild to cold in just 2 or 3 days. For example, on 7th December 2017, temperatures across the southern half of England were mild and widely above 10C. Just 3 days later, midday temperatures over Wales and the Midlands were hovering around freezing, with 20cm of snow lying on the ground! While this a rare and dramatic example of how UK weather patterns can flip during winter westerly spells, don't be too surprised to see a few sharp swings in temperature during this December, rather than sustained mild conditions. Sharp frost and scattered sleet and snow showers are likely on a few days, especially over northern areas.
The silver lining with westerly Decembers is that they can actually be quite sunny! This is especially true over southern and eastern parts of the UK when the monthly averaged wind direction is a little to the north of west. Rain bearing weather fronts tend to be fast moving, with sunny breaks between them. December 2011 was a very westerly month over the UK and sunshine amounts were above average quite widely in the east, despite it also being quite wet.
Further ahead
The lead up to Christmas will soon be in the forecast range! We'll be focussing our attention on pinning down the detail for December and identifying the most likely time for a pre-Christmas cold snap.
https://www.bbc.co.uk/weather/outlook