A mixed festive season: Mild, windy and unsettled with some snow in Scotland

A week ago, the medium-range forecast models, particularly the GFS, were indicating that colder north-westerly winds might establish themselves in the run-up to Christmas, potentially bringing a white Christmas to some areas, especially in Scotland and northern England. It now seems likely that northern Scotland will indeed experience this colder air on Christmas Day, resulting in a white Christmas in certain locations. However, elsewhere, forecasts have shifted away from cold north-westerlies, maintaining a very mild and windy regime across most of the country, dominated by west to south-westerly winds. Southern Britain is expected to remain mild through to the end of 2023, but there is a chance for colder weather with some snowfall in Scotland after Christmas, particularly in the northern regions.

Recent Decembers have generally started on a colder note, and in December 2022, the milder weather towards Christmas was insufficient to counterbalance the cold first half of the month. However, December 2023, despite a similarly cold and snowy start in some areas, is shaping up to be very mild, with temperatures significantly above average following the first week. It has the potential to be the mildest December since the record-breaking one in 2015 in southern Britain.

White Christmases

The Met Office now officially defines a white Christmas as any occurrence of a snowflake falling somewhere in the UK during the 24 hours of Christmas Day. By this definition, the Christmases of 2020, 2021, and 2022 all qualified. However, many people associate a white Christmas with lying snow, and by this criterion, white Christmases have been relatively rare since 2010. In 2020, wintry showers from a northerly direction on Christmas Eve nearly achieved this, but the conditions were not cold enough to result in widespread snow cover at lower levels, with only 4% of Met Office sites reporting lying snow on Christmas Day. In 2023, it is highly probable that this technical definition of a white Christmas will be met due to expected snowfall in northern Scotland, mainly on higher ground, although for most of the UK it will be a mild and snow-free Christmas.

After a period from 1950 to 1970 when white Christmases were quite common in many UK areas, they became rare between 1971 and 1992, with widespread lying snow on Christmas Day occurring only in 1981. There were also few instances of widespread snowfall during this period.

White Christmases then became relatively frequent again between 1993 and 2010. Around 2010, it was noted that December was the only month without a warming trend since the start of the 20th century. However, the past decade has shown indications that December is beginning to join other months in experiencing significant warming.

The most extensive occurrence of lying snow on Christmas Day was in 2010, at the end of an exceptionally cold spell that lasted, with a brief interruption around mid-month, from 25 November to 26 December. 1995 and 2009 also saw at least 40% of Met Office sites reporting lying snow on Christmas Day. Both falling and lying snow were quite widespread on Christmas Day in 1993 and 2004. Snow also fell widely on Christmas Day in 1996, 1999, 2000, and 2001, though it did not settle on the ground in most places during those years.

The Outlook in Brief

The recent spell of mild and windy weather will continue today, except in northern Scotland, where a cold start will give way to a period of snow, particularly on higher ground, before turning mild and windy later in the afternoon and evening. Wet weather will be prevalent in Scotland, especially in the north, and this will extend into Northern Ireland and north-west England after midday. The rest of the country will experience mostly dry but predominantly cloudy conditions. Although it will start off relatively calm in north-east Scotland, windy conditions will prevail across all regions by the afternoon. Temperatures are expected to reach highs of between 10 and 12C generally, except in north-east Scotland, where they will remain near freezing for most of the day before rising to around 5C by midnight.

Christmas Eve and Beyond

Christmas Eve will continue to be windy. It will be very mild in England and Wales, with temperatures generally between 12 and 14C, and locally reaching around 15C. Cloudy weather with some light rain will persist in the south throughout the day, but northern England and north Wales will see a mix of sunshine and showers. Temperatures in Scotland and Northern Ireland will be closer to seasonal norms, with a combination of sunshine and showers, and rain at lower levels but snow in the Scottish Highlands. Windy conditions will persist.

Christmas Day is forecast to be mild, cloudy, wet, and windy for most of the country, with highs of 10 to 12C in much of England and Wales. However, as the rain band moves into southern Scotland, it will bring snow to higher elevations north of the Central Lowlands, possibly with some sleet and wet snow at lower levels for a time. Northern Scotland will experience a bright day with scattered wintry showers. The northern half of Scotland will be quite cold on Christmas Day, with highs between 3 and 5C at lower elevations.

Looking further ahead, cold weather will linger near northern Scotland between Christmas and the New Year, with the potential for significant snowfall on the 27th and 28th in northern Scotland. Elsewhere, the mild, wet, and windy weather will continue to prevail.