Britons are in for an unusual weather event this week, with the potential for temperatures to reach as high as 20C, according to the Met Office. Wednesday is anticipated to be the warmest day of the week, possibly even marking the hottest day of the year so far if temperatures hit the 20C mark. The previous record for this year was set on March 5 in London at 19.2C.
Chief Forecaster Dan Harris from the Met Office mentioned that regions of western Wales and western England could experience temperatures ranging from 18C to 20C on Wednesday afternoon. This temperature surge is attributed to a weather phenomenon known as the “Foehn effect.”
The Foehn effect occurs when moist air rises on one side of a mountain, cools down, and leads to precipitation. As the air descends rapidly over the other side of the mountain, it warms up, resulting in higher temperatures on the downward slope.
In the UK, foehn events are commonly observed in the Scottish Highlands. Moist westerly winds from the Atlantic are pushed over the mountains, causing wet weather in the west while the east enjoys warmer and sunnier conditions.
The Foehn effect is recognized by various names worldwide. In the Rocky Mountains, it is known as ‘the Chinook’ or ‘snow eater,’ while in the Andes, it is referred to as ‘the Zonda.’
Mr. Harris highlighted that Wednesday is likely to be the warmest day of the week for many areas due to dominant high pressure. The warmest regions could be in parts of western Wales and western England, where temperatures could reach 18-19C, potentially hitting 20C under sunny skies, thanks to the Foehn effect.
He also mentioned the significant temperature difference between daytime highs and overnight lows, known as the diurnal range, for the week. Clear skies during the day will lead to chilly nights following warmer days, with some areas possibly experiencing air frost.