They state that the outlook at that range is very uncertain, of course the forecast will chop and change at that time range.

The clue is in the name "forecast" and it will change from day to day @ times as new data and information is used to make the forecast. 

BBC monthly outlook

Monday 16 April—Sunday 22 April

Turning much warmer and sunnier for most

Many areas of the UK will experience their first proper spell of warm springtime weather this week. Warm south to south-easterly winds will develop for a time between an area of high pressure over Scandinavia and low pressure over the eastern Atlantic.

On Monday, there will be fairly widespread spells of sunshine with a rather warm southerly breeze. However, western Scotland together with Northern Ireland will be cloudier at times and windy with occasional rain.

On Tuesday, much of England and Wales is likely to be dry, rather warm and often sunny but Scotland and Northern Ireland will stay somewhat cloudier and breezier with the chance of further rain.

However, by Wednesday, all parts of the UK should become drier and mostly sunny and less breezy. Temperatures will be widely above the seasonal average; reaching the low 20s Celsius quite widely over England and Wales, perhaps locally with temperatures into the mid-20s Celsius.

Thursday and Friday are also likely to be generally warm and bright but winds are likely to become more easterly, bringing the risk of cooler and misty conditions to North Sea coasts then.

By the weekend 21st/22nd, there is some uncertainty over the details of the forecast. However, it looks as though the high pressure area over Scandinavia may weaken allowing one or two fronts to approach from the west. Therefore, some rain seems likely at times for north-western areas of the UK but with very little rain probably making its way to the south and east of the UK; probably often dry and rather warm there.

Monday 23 April—Wednesday 9 May

A little rain for a while. More settled in to May

The last full week of April is likely to see another change in the weather for most with cooler winds from a north or north-west predominating. Temperatures are favoured to fall nearer to the seasonal norm through the week and may even end up a little below average by the end of the week. One or two night frosts cannot be ruled out, particularly for rural areas. Occasionally, rain or showers are likely to make their way southwards across the UK. The best of any longer drier and brighter spells are likely to be over southern areas. Occasionally, it could be quite breezy but no particularly strong winds appear likely. As we enter early May, models indicate that high pressure should not be too far away from the UK, perhaps often positioned somewhere to the west or north-west of the country. Therefore, a lot of dry and quiet weather is now anticipated through this period with only occasional showers or rain. There should be a lack of windy days too. Temperatures are likely to be not too far from the seasonal average; it should feel pleasant in any lengthier periods of sunshine. The main uncertainty through this period is how far south-eastwards high pressure will exert its influence. Highest confidence for often dry, settled conditions is for north-western parts of the UK. Confidence is lower for southern areas.

Next Update

We will take another look at May to see whether the latest guidance still shows signs of some dry, quiet weather.

https://www.bbc.co.uk/weather/outlook

UK Weather forecast shock: Britain to BOIL in record hot sunshine within DAYS

THE UK is just days aways from a record-breaking week of hot sunshine and scorching weather as a colossal storm churning in the Atlantic opens the floodgates to a plume of red-hot air from the tropics.

https://www.express.co.uk/news/weather/946933/UK-weather-forecast-hot-sunshine-heatwave-London-Marathon-weather-latest

UK Outlook for Sunday 22 Apr 2018 to Tuesday 1 May 2018:

Sunday should see fine and warm conditions in the south and east of the UK, however the north and west are likely to have a risk of showers and longer spells of rain accompanied by strengthening winds. Into next week, there are likely to be spells of more unsettled weather with some wet and windy conditions, especially in the northwest. The best of any drier and brighter weather will be in the southeast, but with a chance of some rain at times even here. Temperatures are expected to be above average, and warm at times in central and southern areas. These conditions are likely to last to the start of May, with changeable conditions continuing in the northwest, while the southeast still has some decent dry and bright spells.

UK Outlook for Wednesday 2 May 2018 to Wednesday 16 May 2018:

The forecast through this period is currently very uncertain, but through the first half of May it looks as though we could see a mixture of periods of more settled, fine and dry conditions interspersed with spells of showery and more changeable weather. Temperatures are likely to be around average, but with the risk of some cooler northerly winds at times.

https://www.metoffice.gov.uk/public/weather/forecast 

UK Outlook for Monday 23 Apr 2018 to Wednesday 2 May 2018:

The start of next week sees a return to more changeable conditions, with a mixture of bright and showery weather and some longer spells of rain at times. The northwest is likely to see the most frequent and heaviest showers, as well as the windiest conditions. The best of any drier and brighter weather will be in the southeast, but with a chance of some rain at times even here. Temperatures overall will be back around average, but it may be rather warm in the south and east at times. By the end of the month, confidence in the forecast becomes low, but there are likely to be periods of unsettled, cooler weather, particularly in the northwest, while the southeast still has some decent dry and bright spells.

UK Outlook for Thursday 3 May 2018 to Thursday 17 May 2018:

At the start of May changeable conditions are probable at first, with the southeast seeing the best of any drier, warmer weather, while the northwest has more frequent spells of rain or showers. The forecast through the rest of this period is currently very uncertain, but through the first half of May it looks as though we could see a mixture of periods of more settled, fine and dry conditions interspersed with spells of showery and more changeable weather. Temperatures are likely to be around average, but with the risk of some cooler northerly winds at times.

https://www.metoffice.gov.uk/public/weather/forecast 

UK Outlook for Thursday 26 Apr 2018 to Saturday 5 May 2018:

There will be sunny spells and scattered showers on Thursday, the showers being heaviest and most frequent in the north and northwest with a risk of thunder at times, the driest and brightest conditions being in the south. Conditions will probably be drier on Friday with the showers becoming confined to the north. It will be rather windy on Thursday, but the winds will become lighter on Friday. For the rest of the period it will be generally changeable, with the best of any drier and brighter weather in the southeast, but with a chance of some rain at times even here. Temperatures overall will be around average, but it may be rather warm in the south and east at times.

UK Outlook for Sunday 6 May 2018 to Sunday 20 May 2018:

At the start of May changeable conditions are probable at first, with the southeast seeing the best of any drier, warmer weather, while the northwest will have more frequent spells of rain or showers. The forecast through the rest of this period is currently very uncertain, but through the first half of May it looks as though we could see a mixture of periods of more settled, fine and dry conditions interspersed with spells of showery and more changeable weather. Overall it will be wettest in the northwest, and driest in the southeast. Temperatures are likely to be around average, but with the risk of some cooler northerly winds at times, although there is a greater chance of above average temperatures into the second half of the month.

https://www.metoffice.gov.uk/public/weather/forecast 

UK Outlook for Friday 27 Apr 2018 to Sunday 6 May 2018:

Sunny spells and showers are likely on Friday with some showers heavy with a risk of hail and thunder, especially in the north. Similar conditions are likely on Saturday, but there is a chance of some longer spells of rain developing from the west or northwest. There is also a risk of some snow over Scottish Mountains. It will be generally rather cold with some overnight frost possible in the north. Into the start of May conditions will be generally changeable and windy at times. There will be some drier, sunnier spells, these most likely in the north and northwest. Temperatures will be near or just below average, with only a small chance of warmer conditions.

UK Outlook for Monday 7 May 2018 to Monday 21 May 2018:

There will be generally mixed conditions through May, with some dry spells as well as more changeable periods with rain or showers occurring more widely. There is low confidence in detail, but a more settled spell may develop for a time in early May, especially in the northwest and there are some signs of a generally drier, settled period in the second half of the month. Temperatures are likely to be around average, but with the risk of some cooler northerly winds at times, although there is a greater chance of above average temperatures into the second half of the month.

https://www.metoffice.gov.uk/public/weather/forecast 

Week ahead

Cooler and fresher
Sunny spells
Blustery showers

High pressure returning for some into early May?

https://www.bbc.co.uk/weather/features/43859661?ns_mchannel=social&ns_campaign=bbc_weather&ns_source=twitter&ns_linkname=news_central

That is also starting to back up what I recently said on the Model output thread about May possibly turning out to be OK. At least one member doesn't agree with that but then, the sypnosis doesn't actually look so good for the south of the UK, so that might not be such good news for the southerners on this forum.

I would expect that the north and west of Scotland would probably come out best with that outlook since easterly winds would probably result in the east coast being cooler, and possibly plagued by low cloud and that east coast haar at times.

For here IMBY, that could possibly mean yet more easterly muck for us to put up with and so, the outlook might not necessarily be as good for here as it would appear to be at first glance.

BBC monthly outlook

Monday 23 April—Sunday 29 April

Something more typical of April

Drier for a while on Monday as a shallow high pressure ridge crosses the country but the next Atlantic low pressure system will soon bring more rain and drizzle across northern and western regions traversing England and Wales on Tuesday. Meanwhile Scotland and Northern Ireland find themselves in a showery westerly regime with the west seeing most of the showers. Midweek will be windy and unsettled with showers at times in an unstable west to north-westerly airflow. It won't be significantly cold but temperatures will be near or a little below normal. Drier conditions could develop later on Thursday and into Friday with winds easing as a transient ridge of high pressure arrives. Confidence is low for the end of the week with conflicting model guidance but most likely we'll see further changeable weather with low pressure to the north-west of the UK sending bands of rain eastwards. There is a chance that a ridge of high pressure may build across southern areas for a time over the weekend, but the chance of this is only around 25%. Either way, no extremes of wind or temperature look likely.

Monday 30 April—Sunday 6 May

Generally unsettled. Driest in the south-east.

Towards the turn of the month and through the first week of May it looks like a similar situation will prevail with low pressure dominating and high pressure off to the east. Given that alignment it's not going to be significantly chilly, and in fact southern and eastern areas could warm a little above normal at times. Bands of rain will move across the country interspersed with brighter but showery flows and occasionally brisk winds but nothing notably strong. The south and east will get away with longer dry spells but a little rain should still come through at times.

Monday 7 May—Sunday 13 May

Turning more settled for a time

For the second week of May there are still indications that high pressure will build a little more across west and north-west Europe, and a period of dry and quiet weather should result for many areas with temperatures near the mid-spring average. However, through mid-month there are suggestions of this high pressure subsiding as low pressure systems possibly develop closer by to the northwest, potentially bringing a return to breezier and wetter conditions as associated frontal systems move through. Again, northern and western regions will most likely be in the firing line.

Next Update

Will the trend back towards unsettled conditions for mid to late May still be evident or will high pressure try to dominate again later in May?

https://www.bbc.co.uk/weather/outlook

UK Outlook for Saturday 28 Apr 2018 to Monday 7 May 2018:

Many northern areas will be dry with sunny spells on Saturday, although there remains the risk of some heavy showers. More unsettled conditions will arrive in the south, with a strengthening wind. These changeable conditions are then likely to spread to many parts as we head into early May with showers or longer spells of rain, but some drier and sunnier spells are likely too, particularly in the north and northwest. Winds will be brisk at times, and overall it will feel cool with the risk of frost overnight, mainly in the north. On the whole, temperatures will be close to average for the time of year, but it will feel cooler in the more unsettled spells.

UK Outlook for Tuesday 8 May 2018 to Tuesday 22 May 2018:

Mixed conditions will continue through early May, with changeable periods of weather bringing showery rain, interspersed with drier and brighter interludes. Some longer drier spells are possible across the northwest. Confidence reduces into the second half of May, but there are some signs of a generally drier, more settled spell of weather developing. Temperatures are likely to be variable at first although balancing out around average. If a more settled spell develops later in the month, then temperatures may become warmer than average.

https://www.metoffice.gov.uk/public/weather/forecast 

UK Outlook for Sunday 29 Apr 2018 to Tuesday 8 May 2018:

Northern and western parts of the UK should be mainly dry on Sunday and Monday, except for the odd shower. In the south and east it is likely to be changeable with showers or longer spells of rain and stronger winds. Temperatures will be close to average but along North Sea coasts it will feel colder with easterly winds. Mixed conditions will then continue through the first week of May with brisk winds and spells of rain at times, perhaps with some snow over the Scottish mountains. Some drier and sunnier spells too. Temperatures will remain close to average throughout, but at times it will feel colder with a greater risk of frost overnight, especially in the north.

UK Outlook for Wednesday 9 May 2018 to Wednesday 23 May 2018:

Mixed weather conditions are mostly likely to continue into early May, with showers or longer spells of rain, interspersed with drier and brighter interludes. A more settled spell may develop for a time in early May, especially in the north. Thereafter, there are some signs that from mid-month it may become drier and settled more widely across the UK, although confidence in this aspect of the forecast is low. Temperatures are likely to be variable during this period as is often the case at this time of the year, averaging out close to normal. However, if a drier and more settled spell develops, then temperatures may become warmer than average.

https://www.metoffice.gov.uk/public/weather/forecast 

UK Outlook for Monday 30 Apr 2018 to Wednesday 9 May 2018:

Northern and western parts of the UK are likely to be mainly dry and bright on Monday, apart from the odd shower. In the south and east significant rainfall is possible accompanied by stronger winds. However, there is uncertainty about the time and place of the heavy rain and some areas could get a sunny day. Temperatures will be a little below average and cold enough for a slight overnight frost in the north and north-west. Changeable weather will continue during the first few days of May with brisk winds and spells of rain at times, but a few drier and sunnier spells too. Temperatures will tend to recover to near normal but at times it will feel colder, so overnight frost in the north remains possible.

UK Outlook for Thursday 10 May 2018 to Thursday 24 May 2018:

A dry and bright spell of weather with light winds may develop at the start of this period especially in the north, bringing slightly above-average temperatures. However, confidence in this aspect of the forecast is low. Mixed weather with showers or longer periods of rain remain possible. In fact, there is a signal for a greater number of heavy showers than usual in the south, perhaps including thunder at times. Where the weather does becomes wet and windy, temperatures will drop down to average or a little below.

https://www.metoffice.gov.uk/public/weather/forecast