MONTHLY WEATHER FORECAST FOR THE UK
UPDATED 6TH DECEMBER - 13TH DECEMBER - 4TH JANUARY 2021  
 

Mild and unsettled start, then turning dry and quite cold with high pressure

Mean temperatures will be 1 to 1.5C above the long-term normal over much of Scotland, with the largest positive anomalies in northern Scotland, but within 0.5C of the normal in central and southern parts of England and Wales. Most other parts of the UK coming out 0.5 to 1C above normal.

Rainfall totals will tend to be below normal, except in north-west Scotland where they may come out near normal, but there is potential for the weather to turn drier for north-west Scotland too into late December.

There is high uncertainty over sunshine totals as it is hard to forecast at this range whether the anticyclone of mid to late December will be a predominantly clear and sunny high or a cloudy one. Sunshine is most likely to be above normal in the east and below normal in the west early in the period, but towards the New Year, it is more likely to be the other way round, with western areas sunniest relative to normal.
 

Week 2: Monday 13th December - Sunday 19th December

This week looks set to be mild with mainly south-westerly winds, and low pressure systems moving from south-west to north-east to the north of Britain. Early in the week it will tend to be unsettled, with fronts moving in from the west at frequent intervals, interspersed with brighter, showery weather, with most of the showers towards the north-west. In the showery interludes, the showers are likely to be wintry at times on high ground in the north, but probably not at low levels.Later in the week, high pressure will slowly build from the south, turning the weather drier and more settled in central, eastern and southern England and in south and east Wales. Rain belts will continue to affect north-west Scotland, but will make limited progress into other parts of the UK. The end of the week may turn colder in the south, with high pressure and light winds resulting in some frost and fog patches developing overnight, but it looks set to stay mild in the north. There is some uncertainty in the timing of this trend, but fairly high confidence in the weather turning colder and more settled in the south by the early part of Week 3. Temperatures are thus forecast to be above the 1981-2010 long-term normal during Week 2, typically by 2 to 3C in most regions, but more likely to be 1 to 2C above in north-west Scotland and also in southern England. Rainfall totals will be above normal in north-west Scotland, but near to slightly below normal in most other regions, with a wet start to the week being at least offset by drier weather later on. With a generally south-westerly flow, sheltered parts of eastern Scotland and north-east England will generally be drier than average. Sunshine totals are expected to be mostly above normal in the east of both Scotland and England, but below average in Northern Ireland, western Scotland and north-west England.
 

Week 3: Monday 20th December - Sunday 26th December

There is a strong signal for high pressure to dominate during this week. Westerly and south-westerly winds on its northern flank will bring relatively mild weather, especially early in the week, to much of Scotland and Northern Ireland, but it will turn colder over England and Wales generally, and this colder, settled regime looks likely to extend to most parts of Scotland and Northern Ireland later in the week. Sunshine amounts are somewhat more uncertain, as anticyclonic gloom is quite common at this time of the year. With high pressure dominant, it will be generally dry, so a white Christmas currently looks unlikely, but can't yet be completely ruled out in eastern Britain, as in these high pressure setups we do sometimes get brief cold blasts from the north or east with wintry showers for eastern areas in particular. The most likely outcome for the Christmas period is for it to be dry with variable amounts of cloud and some overnight frost and fog. As a result, it will be drier than average everywhere, with temperatures most likely to be 1 to 2C warmer than average in northern Scotland, but up to 1C colder than average in central and southern parts of both England and Wales. Sunshine could vary either way from the long-term average depending on how much cloud and moisture becomes trapped in the high pressure area.

Rest of month: Monday 27th December - Tuesday 4th January

Confidence is lower for this period but there is a greater chance of colder weather heading in from the east at some point during this period as highest pressure transfers further north, most likely towards Scandinavia, so there is potential for some snowfalls, but not a certainty, as much depends on the specifics of the wind direction and the extent of cold air masses over the near Continent. It looks set to remain generally drier than average, but possibly less so than during Week 3, especially for eastern parts of the country. Sunshine totals are most likely to be below normal in the east, but above normal in the west. Overall, temperatures are most likely to be a little below normal for most of the country, with negative anomalies of around 1C, but near average temperatures are more likely in northern Scotland.

Courtesy of Netweather