Gales, a brief chill, then milder – but nothing unusual

The British weather is going to live up to its reputation for being very changeable later this week, with a variety of things to keep an eye on.

However, it is December and it’s a time of year when we would expect the weather to throw everything at us apart from the kitchen sink.

The reason for the active weather in the coming days is cold Arctic air colliding with milder sub-tropical air in the mid-Atlantic, giving a strong temperature contrast over a relatively short distance.

As the speed of the jet stream is driven by temperature contrasts in the atmosphere, this will give it a boost – hitting 190mph five miles up in the sky on Thursday.

This will spawn a deep area of low pressure that will first of all bring us some very windy weather on Thursday, followed by a burst of Arctic air on its backside as it pulls away into Friday.

Strong wind

As the deep area of low pressure passes just to the north of Scotland during Thursday, there’s going to be a spell of very windy weather – especially for the northern half of the UK.

Scotland, Northern Ireland, as well as northern parts of England and Wales, will see gusts as high as 70mph coinciding with the morning rush hour. Exposed coasts and hills in northern Scotland could see gusts a little stronger at 80-90mph.

This strength of wind will have the potential to cause some problems, with a risk of a few trees and power lines being blown down, as well as some disruption to transport. The gales will also generate some large waves which could give localised coastal flooding.

For the rest of the UK, it’ll be windy, but not as windy as further north, with gusts of 40-60mph.

Cold air and snow

As the area low pressure pulls away later on Thursday, the wind will change to come from a northerly direction, allowing very cold Arctic air to flood southwards into Friday.

This will give some snow showers to coasts and hills exposed to the wind, however, significant snow fall is likely to be confined to northern Scotland. Here, 2-5cm could accumulate on low ground, with 10-20cm over the higher hills and mountains.

For most of us, though, there won’t be any snow at all – just sunshine and a raw wind accentuating the chill.

Temperatures on Friday will be around 0-3C for Scotland and northern England, with 3-8C elsewhere.

Milder this weekend

Despite some of the recent Daily Express headlines claiming that the UK is in for 100 days of heavy snow, the cold weather is only going to stay with us for a day before temperatures pick up to average this weekend.

Looking further ahead, the key to what happens later in December depends on where a big area of high pressure grinds to a halt.

At the moment, there’s a split in its potential position, with some weather models bringing the cold weather back mid-month, whereas others keep it mild.

In the meantime, you can get the latest forecast on the Channel 4 Weather website. I’ll also be posting regular updates on Twitter – @liamdutton