Friday evening sees any showers fading. A low pressure for Saturday will bring wet and blustery weather from the Atlantic with some proper rain before it clears northwards. Sunday looks sunny with scattered showers.
After such a lot of dry, sunny and warm to hot weather, the end of August is rather mixed. The air flow feels fresher now. However, in any sunshine, there is still a good deal of warmth lifting temperatures into the low 20sC for the middle of the week. There will be a scattering of showers from the west and bands of rain bringing heavier falls with darkening skies. As one of these passes by, the temperatures will fall. Pinning down the details of these, in terms of timings, remains tricky. It will be worth keeping an eye on the Netweather Radar for the individual showers and the progress of any rainbands as they move eastwards.
The current steer for our UK weather is a low pressure to the northwest, which was linked to the remnants of Hurricane Erin. Out at sea in the Atlantic is Tropical Storm Fernand, which will become extra-tropical as it moves across the ocean but gets entrained in developments along a frontal boundary. It adds its tropical energy and moisture to a new wave and resulting low pressure, which will be over Ireland by Saturday. Now, if you have an event at the weekend, you might have noticed that weather apps keep changing; when it's wet and when it's dry. It’s down to the developing low pressure and where it might be in relation to the UK.
The low centre is further north on Wednesday's model run
There has been some variation about how far north this low centre will head. The Met Office model had it positioned over southern Britain on the output on Tuesday, but has now come into line with others holding it to the west or northwest of Ireland. The ECMWF, Arpege, and GFS models are all in agreement on this position, but the timing of the frontal rain also varies slightly. There will be some heavy rain on these fronts. Moreso for western and upland areas, and the chance of blustery winds, even strong gusts. We desperately need the rain, but you just might not want it on Saturday.
Movement of the frontal band shown on the ECM model on Saturday from Ireland to Scotland and western Britain by the evening
For the weekend, Friday evening will bring a lot of fine weather with bright or sunny skies. There will be a scattering of showers, particularly over Northern Ireland and Scotland, as the showers over southern Britain fade slowly from London and the Home Counties.
Most of the UK will be dry and clear overnight, with just a few showers for NW Britain. It will be cooler with temperatures of 9 to 13C with light winds.
Saturday
Depending on the timing of the incoming frontal bands, eastern Britain and the north of Scotland should see fine, sunny and warm weather on Saturday morning.
Two runs of the GFS model show the low centred to the north of Ireland and gusty southerly winds through the Irish Sea
Through the day, the southerly wind will pick up, backing and strengthening for Northern Ireland around the low centre. It will become windy around the coasts of SW Britain through the Irish Sea and the North Channel, which might make ferry journeys a bit lumpy. Gradually, the fresh S to SE winds will reach over more of Britain, although northern Scotland should get away with a quieter day.
There is quite a balance here, warmth in the sunshine before the rain with a southerly flow which could allow temperatures to reach 23 or 24C in some spots. Then the incoming rain and blustery winds will change the day and make it cooler.
This far ahead, we can’t hold onto exact timings for when the rainband will arrive over Cardiff or Manchester. It will move east and north through the day with a clearance for Northern Ireland by Saturday evening as the wind veers to a southwesterly.
The UKV rainfall totals for 24 hours hint at some gaps, to the lee of high ground in the southerly flow, and East Anglia. There are higher totals over South Wales, the Welsh mountains, the Lake District and the Yorkshire Dales, the Peak District and the west coast of Scotland.
Again, depending on the timings, there could be outbreaks of rain over eastern Britain and the northern half of mainland Scotland through Saturday evening with clearer weather from the southwest. This will spread to most of Britain overnight.
Sunday
Around the low centre, sharp showers and gusty winds will continue. As the frontal band clears northwards over the Northern Isles, there will be a rash of showers into western Scotland, for the north coast of Northern Ireland and a scattering coming into western Britain. For many, Sunday looks fine, bright or sunny but sometimes breezy. East Anglia will see the highest temperatures up to 23C and to the lee of high ground with stronger winds, Moray and Aberdeenshire could see temperatures into the 20sC. During the afternoon, it will be windy in the north with lots of showers, further south just a scattering. And sunny spells in between. In any sheltered sunshine, it will feel warm, but for more western areas, exposed to the wind and as showers pass by, it will feel fresher.
So, fading showers for Friday evening and a lot of fair weather. A change on Saturday as this low pressure brings a spell of wet and windy weather, then it clears and we’re back to the mixed sunny spells but risk of showers on Sunday.
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