Cold weather set to return

After the cold weather of recent weeks, a burst of energy from the jet stream has brought mild, wet and windy weather to our shores this week.

Following this week’s milder interlude, temperatures will see-saw this weekend, before taking on a downward trend through next week.

I explained in my blog a few days ago that the return to colder weather is due to the jet stream taking a more north to south track across the Atlantic, rather than the usual west to east.

As a result, high pressure will build for a time in the mid-Atlantic, pushing warm air northwards towards Greenland and allowing a surge of cold Arctic air to push southwards over the UK.

Whilst there will no doubt be some excitement that the return of colder weather could lead to snow, I think that it won’t be anywhere near as widespread as it was in the last cold spell.

In fact, I’d go as far as to say that many places will see little, if any snow at all, largely thanks to the proximity of high pressure giving a lot of dry weather.

Falling temperatures

After a chilly but sunny day on Saturday, milder air will temporarily return on Sunday. The real surge of colder air arrives during Monday, when a north westerly wind drags Arctic air across the UK.

Although it is going to turn colder, it’s unlikely to be quite as cold as last week, when temperatures struggled to get above 0C all day.

For most of next week, daytime temperatures are likely to be in the range of 2C to 6C, with the lowest temperatures across northern areas. At night, temperatures will be in the range of -5C to 0C.

I think the main factor that will make it feel cold next week will be the strength of the wind.

Cold, dry, rapidly moving air is very efficient at evaporating the moisture in our skin – cooling it down, just like evaporating sweat does during hot weather. As a result, this makes us feel colder than the temperature shown on a thermometer.

Some snow, but not for all

When the wind blows from a northerly quarter, the air that moves towards us is inherently quite dry having originated from the Arctic. As a result, the only source of moisture as it moves towards the UK is from the relatively warm water that surrounds us.

As cold air moves over a relatively warm sea it becomes unstable as it is heated from below, causing pockets of moist air to rise, forming clouds and heavy showers.

These showers are then carried by the wind and blown towards the UK. However, because their main source of energy is the relatively warm water, generally, as soon as they move over land they fade quickly.

That is why next week you’ll commonly hear me and other weather folk say: “Lots of showers for coastal areas, but inland it will be largely dry and sunny.”

As always in weather, there will be exceptions to this general rule and these will come in the form of troughs. These are more active bands of showers that are more potent and have a longer lifespan. As a result, they can move further inland than would normally be expected.

So, for now, it looks like coastal counties in northern parts of the UK will have the greatest chance of sleet and snow showers next week. The rest of us will have the pleasure of crisp, winter sunshine and frosty nights.

Don’t forget, you can get the latest forecast on the Channel 4 Weather website. You can follow my regular updates on Twitter – @liamdutton