For much of the UK, there will be plenty of fine, dry weather with warm sunshine. High pressure is bringing settled weather although with some early mist and fog. This reflects the setup of light winds and enough clear spells overnight for the air to cool off. There is a significant low pressure that will affect Iceland today. Already there are warnings for the south of the island including, unusually for September, the capital Reykjavik which mention storm-force winds today.
For the UK gales, even severe gales are possible in the far NW later today. There is a huge frontal boundary stretching from the Icelandic low right down to another low in the Atlantic. This one is a “storm force, non-tropical low pressure, the remnants of Odette” NHC. The cold front in between will move south over Scotland early on Wednesday as the northern low continues to deepen. The high pressure is still to the south of Britain, but as other lesser lows move by to the north there will be weather fronts dangling over the UK. These will bring a bit more cloud, even some patchy rain to western shores but for many, there is a lot of fine, dry weather this week.
The Atlantic jetstream is having a turbo boost, with speeds up to 180mph. It is further north and it's steering most of the low pressures to the north of the UK, hence Iceland's stormy Tuesday. When the jet is further south, those low pressure come right at the UK from the west and then we know that autumn has arrived. Highland Scotland will be getting a taster but further south and east, many will be oblivious.
The strong winds in the north will become quite a feature of the weather this week as bouts move through. SW winds tonight for northern Scotland with gales, even severe gales this evening for the far NW, strong W winds for the early hours of Thursday for northern Scotland with gales for exposed coasts and hills. Windy again overnight into Friday with strong W winds affecting more of the UK through Friday, particularly NE Britain. And even later on Saturday for NW UK as south-westerly winds look to strengthen once more as the daylight begins to fade.
Today’s UK temperatures will be around 16 to 21C, again feeling warm in the sunshine but cooler in the breeze and when the cloud increases. For Northern Ireland and western Scotland where it will be damp in the west and grey by this afternoon with rain cloaking the NW Highlands for a time.
Tonight, as the cold front edges in from the far NW there will be heavy rain by dawn from the Northern Isles, through Highland and the Western Isles. This band will slowly edge its way southwards through Scotland on Wednesday into Northern Ireland by the evening. Eastern Scotland will see patchy rain in the morning, but the band keeps together into the evening. This will be quite a change after a dry spell for many areas. That first main front reaches across Wales by Thursday morning, with more cloud for the Midlands as another frontal band pushes down from northern Scotland.
For southern Britain, it looks a bit warmer by Thursday and Friday from 19 to 24C with sunshine. There could be more cloud around by Saturday but in any breaks, it will again be warm and on Sunday. Just more chance of low cloud and dampness for SW England and Welsh coasts.
By Sunday a more sturdy weather front, running north-south, looks to approach the UK from the west. Another low centre nearing Iceland but by the end of the weekend, high pressure looks to be over Scandinavia which could block the incoming rain band. In between the two, there would be a feed of warmer air from the south ready for the start of next week.