BBC monthly outlook
Summary
A cold outlook with changeable weather.
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Wednesday 7 April – Sunday 11 April
Cold returning by the end of the week.
Nobody really needs reminding that the Easter period saw a big change in the weather. Cold north-westerly winds brought snow showers, with temperatures dropping well below normal everywhere. A weak and transient ridge of high pressure will bring drier conditions for a while on Wednesday. Winds will back more westerly, so it will become less cold for Thursday, although not warm by any means.
Bands of rain will slowly move across the UK from the northwest as a low pressure system passes just north of Scotland. There will be stronger winds for a while, especially across Scotland and Northern Ireland. The front will weaken as it moves farther southeast, and the south of the country could stay dry and fair for longer. But there will be some rain on Friday. Behind this front there will be colder air returning, and that will cause snow showers to come back to northern Scotland and Northern Ireland during Friday and Saturday.
Some of the snow will drift southwards into southern Scotland and northern parts of England and Wales, although these should be few and far between. However, the cold air might not get all the way south, and southern England should be less cold with a little rain possible at times. Unsettled weather will continue through the end of the week with north to north-easterly winds. There will be showers scattered around, mostly rain across South Wales and central and southern England. There will also be sleet and snow for North Wales, northern England, Northern Ireland and Scotland. Southeast England could see some more persistent rain lingering, thanks to the proximity of a low pressure system sliding from northern France through the Low Countries to northern Germany.
Monday 12 April – Sunday 18 April
Becoming less cold but still unsettled.
Unusually cold air will linger into start of next week, with low pressure to the north and northeast bringing in Arctic air. Southern areas will be less cold with respect to average than the north. It will remain unsettled, with scattered showers of sleet and snow, most of them in northern and eastern regions. Isolated flurries will be possible almost anywhere. Some showers will mix with rain, though, especially in the east and south.
The brisk and cold winds will ease, as we head into the second half of next week. Temperatures will be nothing to write home about, though, staying just below average, or near normal at best. Low pressure will move farther way to the northeast and a high pressure ridge looks like it could develop, extending northwards from France. This should bring some drier conditions for a while, with chances that it will grow into a somewhat stronger area of high pressure over the UK by the end of the week. This would steer low pressure systems away, bringing calmer and drier conditions by the end of next week.
It would stay a bit chilly, though. However, there is a lot of uncertainty on this and the model guidance is split with a large divergence. Some ensemble forecasts support this scenario while others paint a very different picture, showing a developing low pressure system moving in from the southwest. That would bring rain right across the country with stronger winds but also milder air, and this has about a 35% chance of being realised.
Monday 19 April – Sunday 2 May
Settled for a while then changeable later.
The latter part of April most likely starts with high pressure lingering and producing a rather quiet spell of weather. It should be cool for the time of year, or even chilly, but not close to being as cold as the first half of April. It will also be dry for much of the time with relatively light winds in most areas and some sunshine, although overnight fog will be a risk. This high pressure should block the path of any low pressure systems and tend to steer them more towards the Arctic, although trailing fronts might just bring some rain to Scotland at times.
Meanwhile, low pressure could also develop towards Spain and the western Mediterranean, and perhaps nudge northwards across France. This might cause some rain to move towards southern parts of the UK now and then. Later in April, however, it looks like the high will be on the move, most likely drifting westwards into the Atlantic. This will also bring the return of low pressure systems and more unsettled weather by the end of April and into early May. There should be some warmer periods, but most likely only lasting two or three days, with very variable temperatures, and cooler-than-normal conditions otherwise. Confidence is low, though, with continuing disagreement between models and with statistical forecasts.
An alternate scenario would be for high pressure to shift eastwards into mainland Europe rather than westwards, opening the door to Atlantic low pressure systems. These would bring much wetter and windier weather. There will also be milder conditions with winds more likely to come from the south and southwest. This has about a 30% chance of developing.
Further ahead
There should be a little more clarity on next week's developments - high pressure developing as expected, or will it be wiped out but a developing Atlantic low? And what about the later month? Which way will the expected high pressure shift?
https://www.bbc.co.uk/weather/outlook