A unique weather phenomenon is anticipated to affect the UK on Christmas Day, as per the latest forecast from the Met Office. The Met Office predicts unsettled weather conditions during the Christmas period, with low pressure expected southwest of the UK and high pressure moving in from the east across northern regions.
The forecast for December 21 to 30 indicates a prevailing easterly flow and rain becoming more concentrated in southern or southwestern areas. As Christmas approaches, high pressure is projected to dominate, bringing drier and calmer weather conditions.
Temperatures are likely to decrease compared to recent weeks, possibly falling below average in some areas. While extremely cold conditions are not expected, the Met Office warns of a rare occurrence known as freezing fog becoming more widespread.
Freezing fog is described as a rare event that occurs during winter when temperatures are near freezing, under clear skies and calm conditions. It forms similarly to regular fog, where cooling of the land overnight leads to moisture condensation into tiny water droplets causing fog to develop.
When fog forms in sub-freezing temperatures, the water droplets remain liquid due to the lack of a freezing surface. These supercooled water droplets freeze upon contact with surfaces, creating a white deposit of ice crystals known as rime. Rime formation is common at higher altitudes but rare at lower levels in the UK.
According to America’s National Weather Service, freezing fog can create hazardous conditions, particularly black ice on roadways. Travelers are advised to exercise extreme caution and drive slowly in icy conditions to avoid accidents. Additionally, freezing fog can pose risks to aviation by forming a layer of ice on aircraft surfaces, making flights perilous without proper de-icing measures.