High latitude blocking is set to be a major player in the UK's weather during the remainder of November and into December. It's a generally cold pattern, but early in the season with warmer than normal seas, it's not likely to be a clear-cut, cold and snowy picture countrywide.
A week ago, it appeared likely that we would experience a dry and fair cold spell of weather through late November and early December, followed by milder, changeable south-westerlies arriving in early to mid-December.
We might still enter a mild and changeable regime by mid-December, but the outlook has become less clear-cut. Instead, we're anticipating a period of extensive high-latitude blocking towards the end of November and into early December. This pattern is expected to bring a high frequency of northerly and north-easterly winds across the UK. When the Atlantic frontal systems begin pushing in from the west, likely during the second week of December, they may struggle to progress against the blocking anticyclones to the north of Britain.
Traditionally, such setups are associated with cold and snowy conditions. Although early in the season, the end of November and December have occasionally produced cold, snowy outbreaks. Since the turn of the 21st century, the most notable instance was in 2010, leading to a record-breaking cold December.
However, the absence of significant cold spells this autumn means sea surface temperatures in the North Sea are relatively high for this time of year. Moreover, North Atlantic sea surface temperatures remain at record highs. Given these elevated global temperatures, the northern blocking and the northerly and north-easterly winds may struggle to bring much snow, particularly at lower elevations, where precipitation is likely to occur with temperatures between 1 and 4°C. On higher ground, particularly in the north, there is more confidence in predicting a generally snowy period.
Currently, we are experiencing a northerly outbreak. While not exceptionally cold for this time of year, many areas have experienced frost, and today's weather is set to be cold and sunny for most of the country. High cloud will increase across Northern Ireland, Wales, and the West Country during the afternoon and evening ahead of a frontal system from the west. However, sunny conditions will prevail for the rest of the day. A few showers, primarily rain, will affect some North Sea coastal areas but are expected to diminish after midday. Temperatures will be below the seasonal norm, with most regions seeing highs of between 4 and 6°C.
A milder night is forecasted in Northern Ireland, south-west England, and much of Wales, with cloud and rain spreading from the southwest. Temperatures are unlikely to fall below 3°C. Elsewhere, it will be a cold night with further frost, with temperatures in most parts of England and Scotland dropping close to or slightly below freezing.
Sunday will bring cloudy and wet conditions to Northern Ireland, Wales, and south-west England. The cloud and rain will spread eastwards across the southern half of England and into northern England by the evening. Snow is expected on higher ground in the Midlands and northern England, but elsewhere, precipitation will predominantly be rain. Temperatures will peak at around 8°C in Northern Ireland, south-west England, and south Wales, while highs of 4 to 6°C will be typical elsewhere. Scotland can expect a generally dry and cold day with abundant sunshine north of the Scottish Lowlands, although some showers may spread into northern Scotland later in the day.
Monday will see rain in England gradually clearing south-eastwards, with brighter conditions to the north and west. As a north to north-east wind develops, frequent showers are expected in northern and eastern areas, bringing sleet and snow to higher ground. However, at lower levels, showers will largely consist of rain or hail. Through Tuesday and Wednesday, showers will become more confined to north and east-facing coasts, and widespread frost is expected at night. Daytime temperatures will remain similar to those over the weekend, with most places reaching between 4 and 6°C, but around 8°C in the south-west.
The potential for snow to reach lower ground increases from Thursday onwards. It appears likely that a frontal system will move eastwards across southern Britain, with potential snowfall on its northern flank. As this system moves out into the North Sea, colder northerlies will follow, bringing wintry showers to lower levels in the north and east. While confidence is high that this colder regime with blocking highs to the north and north-west of Britain will persist until next weekend and into the early part of the following week, widespread snow on lower ground remains uncertain.
