The Met Office says recent warm weather is at an end as it issues an alert of conditions changing across the country thanks to an active jet stream. The forecaster says to expect spells of rain and wind for most areas.
The weather this weekend will largely see a northwest/southeast split, with rain expected for much of Saturday and Sunday in the west of Scotland, while the southeast can expect calmer weather with only a small chance of a few brief interludes of showers. In the south, temperatures are expected to remain rather warm for the time of year, likely peaking at around 24C in London on Sunday.
Then next week a strengthening of the jet stream – which plays a crucial role in driving weather systems towards the UK – looks set to bring spells of unsettled weather through for much of the country, although there will still be some periods of drier weather, most likely in southern and central areas.
Met Office Deputy Chief Meteorologist Dan Rudman said, “The strengthening of the jet stream increases the chances of low-pressure systems developing over the Atlantic being pushed towards the UK. Although there are still some details to be determined on the depth and timings of these lows, what we do know is that there’s some unsettled weather on the way next week, with some strong winds likely from the middle the week, especially in the north.
“Weather of this nature isn’t unusual in a UK spring, with changes in the jet stream frequently bringing interludes of unsettled weather.”
Unsettled weather looks likely to continue through the latter part of next week with some longer spells of rain possible in northern areas. The best of any sunshine is looking to be most likely in the south and southeast.
Although it’s a long way off, there are signs that although the following week may start unsettled, it may start to become more settled, for the south in particular.
A Met Office spokesman said: "We’re still some two weeks away from the Jubilee Weekend, but the long-range outlook shows a trend for some possible warm weather in southern areas, and closer to average temperatures further north. The full forecast for the Jubilee Weekend will become clearer nearer the time."
What is the jet stream?
According to the Met Office, the jet stream is a core of strong winds around 5 to 7 miles above the Earth’s surface, blowing from west to east. The jet stream causes changes in the wind and pressure at that level.
It acts a bit like a vacuum cleaner, sucking air out of the top and causing it to become more intense, lowering the pressure system. The lower the pressure within a system, generally the stronger the wind, and more stormy the result.
A slower, more buckled jet stream can cause areas of higher pressure to take charge, which typically brings less stormy weather, light winds and dry skies. Air is constantly moving around the Earth to spread heat and energy from the equator to the poles.
Three large groups, or cells, in each hemisphere help to circulate this air within the lowest part of the atmosphere. The jet stream exists largely because of a difference in heat, which in the northern hemisphere means cold air on the northern side of the jet stream and warm air to the south.
