Updated 15th December
Covering the period 22nd December - 13th January
Changeable and fairly mild, but a cold dry spell likely towards mid-January
Relative to the 1981-2010 reference period, temperatures will be slightly above the seasonal norm in southern Britain, but slightly below in Scotland, while in Northern Ireland, Wales and northern England they will be very close to average. Rainfall totals will be below normal in eastern Scotland, north-eastern England, Lincolnshire and East Anglia, but close to normal in most other parts of the UK, with south-west Scotland and north-west England having above average rainfall.
Sunshine totals will generally be a little above average, but with a shortage of sunshine expected in south-west Scotland and in Northern Ireland.
Monday Monday 22nd December- Sunday 28th December
This period will be dominated by westerly and north-westerly winds, with low pressure dominant over Scandinavia and pressure above average in the mid North Atlantic. As a result, a mix of mild damp west to south-westerly incursions, and colder bright showery north-westerlies, is expected during this week.
The north-westerly incursions may bring some short-lived snowfalls to Scotland and the higher ground of Northern Ireland, England and Wales, but with significant accumulations of snow likely to be restricted to high ground in Scotland. Thus, a widespread white Christmas in the snow lying sense is looking unlikely, but a bookies’ white Christmas (sleet/snow falling) is still a possibility, mostly for Scotland, Northern Ireland and northern England, depending on the timing of the north-westerly blasts.
The mild moist spells will bring some heavy persistent rain over and to the west of high ground, particularly in western Scotland and Cumbria, but sheltered parts of eastern Scotland and north-east England will see little, if any, rain, particularly in counties bordering the North Sea. Strong winds are also expected to feature, with gale force winds likely for Scotland and northern England, with a smaller chance of gales further south. These may cause some structural damage, mostly on high ground and near to west-facing coasts.
Temperatures during this period will be around 2C above the 1981-2010 average in the southern half of England and in south Wales, but close to average in the northern half of Scotland, and around 1C above elsewhere.
Rainfall totals during this period will be above average in western Britain with south-west Scotland and Cumbria likely to report the largest excesses. Eastern Scotland and north-east England will be drier than average, while elsewhere close to average rainfall is expected.
Sunshine totals are likely to be below normal in central and western parts of the UK with a particularly large shortage of sunshine in south-west Scotland, but in the east of the country sunshine totals will be near or slightly above average.
Monday 29th December - Sunday 4th January
High pressure will remain stronger than usual around the Azores which means that significant cold snowy spells are unlikely, but the jet stream is expected to slow down during this period with fewer depressions moving from west to east, which means that more significant colder, drier, brighter spells are likely in between the mild and moist interludes associated with weather fronts. However, any snowfalls are again likely to be short-lived and largely confined to parts of Scotland.
This period is thus likely to be drier than average in the eastern half of the UK but with close to average rainfall likely in the western half of the country. Temperatures are likely to be slightly above the seasonal average in western and southern Britain, but most of Scotland and the eastern side of England are more likely to have close to average temperatures. Sunshine totals will be below normal in Northern Ireland but elsewhere they are likely to be above average.
Rest of the month
Monday 5th January - Tuesday 13th January
This period is likely to see a change to a more blocked pattern. The early part of the period is likely to be generally milder than average, but late in the period, as we head towards mid-January, generally colder and drier than average conditions are expected, although at this range it is uncertain whether the outcome will be snowy, as much depends on precisely where the blocking highs develop. Overall, temperatures during this period will be slightly below the seasonal norm, with western Britain significantly drier and sunnier than average, while eastern Britain is more likely to have close to average sunshine and rainfall amounts.