Following a 3-5 day period where the UK has been positioned to the north of the jet stream and tucked beneath a cool high, skies have been generally fine, dry and fairly sunny by day, clear, cold and frosty by night, the pattern grows complex over the next 7 days and rather congested too. The ‘blocky’ pattern with the evolution of not one but THREE high pressure system’s will grind the overall west to east low pressure train across the Atlantic to a halt. There are countless embedded centres which will continue to develop as the long wave trough complex begins to squeeze this energy as it has nowhere to go. A high to the north, south and east will stop movement and so the low which crosses us tonight will be set to spend ther best part of 4 days either over us or just offshore. This low will take a painstakingly slow loop over Northern Britain over the next 90 hours before a weakness develops in one of the ridges which releases some of this energy and allows the movement to resume.

Here comes the rain bearing frontal boundary which wipes out the high from Britain and brings a return to low pressure dominance.

Once this front sweeps across the UK, the low stalls and so too does the front which will carry the rains in tonight and tomorrow. While winds go northwesterly late tomorrow with sunshine and showers to follow the main soaking, it’s the north of Scotland which will find themselves beneath that stalled front and so rains tomorrow afternoon may keep on pouring right through till late in the day Friday. With the low continuing to go nowhere but take loops, that front will swing back south spreading rains back south again Saturday and most likely Sunday into Monday.

You can see in the GFS pressure charts for Friday, Saturday and Sunday that the low spins on, stalled off the Scottish East Coast.

Friday

Saturday

Sunday

Even once you go out to 120 hours which is by Monday, the UK remains sandwiched and dominated by a mass of low pressure which practically covers the Atlantic from Canada to Europe but it’s the high’s on 3 sides which is stopping any of this from going anywhere. This set up not only poses a concern for rainfall amounts and the flood threat over the next 3-5 days but what’s bundling over the Northwest Atlantic is concerning, especially given what the GFS is pointing towards for Wednesday.

The latest GFS is pointing to a potentially stormy scenario come later Tuesday into Wednesday as the low which will dominate over the next 90-120 hours finally slides on southeastwards, the bigger system which is becoming quite the monster over the Davis Straits will slide and bundle as it heads UKbound and by Wednesday, the latest GFS has this system with multiple centres piled into one, as a sub-977 mb low crossing the UK. This could not only bring yet more heavy rains but also significant winds also.

Looking at various surface and upper analysis off the GFS and ECMWF, it’s safe to say that not only does colder air fill Scandinavia in the next 2 weeks but the low pressure train will keep on going for the UK.

Here’s the upper chart off the ECMWF looking out to next week. Note the trough digging down over Scandinavia with colder air dropping south. This will make for much cooler days and increasingly colder nights.