15/01/2016 Weather for the Week Ahead

Hello, it's cold and getting even colder this weekend.

When will the mild air return? That is such a big question.

If anything, the forecast for next week has become even more

uncertain than it was this time yesterday.

More than that in just a moment.

First of all, let's focus on this cold spell.

Follow the isobars, they point up to the Arctic.

That is where our air is coming from.

Low pressure clearing away from the east.

Still a few showers across East Anglia,

but the winds will be a little less vicious on Friday.

Some snow showers across parts of the west and the north-east

of Scotland through the day, but for many it's a dry, bright

very cold day.

3 to 6 Celsius. And feeling even colder.

And getting colder still on Friday night,

it could well turn icy, particularly where we've got any showers.

The showers fading in the west but will continue to feed sleet

and snow showers across eastern parts during the course of the night.

And those temperatures tumbling, towns and cities a couple of degrees

below freezing, in rural areas well below, negative double figures

where there's snow lying on the ground across Scotland.

It's a really cold start, then, to the weekend.

Could be some mist and fog around,

and we'll continue to see some showers in the east,

rain on the coast, but inland they will be of sleet and snow.

But for the majority it's another cracking, sunny, sparkling,

very cold day.

We could see thickening cloud bring a bit of wet

weather across parts of Northern Ireland later on.

And we may see this weather front bringing a bit more wet

weather across the far north-west,

but for most, high pressure dominates into Sunday.

It's going to be another day of sparkling sunshine

although it could be foggy first thing.

And it will be certainly very cold first thing,

Temperatures on Sunday morning -8, -9, -10, maybe even lower, again,

where there's the snow lying on the ground.

High pressure means it's probably going to be a frosty start to Monday,

but after that the forecast gets complicated. Low-pressure systems

trying to arrive, trying to reintroduce the milder air.

What we know about next week, it will start cold and frosty,

it will probably be milder by the end of the week, but the timing

of that change back to milder weather is very, very uncertain. Why?

Well, a couple of reasons...

The first one - we need to look not just at the cold air

across the UK

but the intense cold across the north-east of the United States

and eastern Canada, which has in recent days led to scenes like this.

That cold air digging south,

hitting against the warm air, providing a contrast,

and it's that contrast which intensifies the jet stream,

that fast-moving ribbon of air high up in the atmosphere, it's driving

southwards and that contrast then forcing the jet stream further north.

Allowing this pool of warm air to be sitting in the middle

of the Atlantic.

The jet stream then comes back south

and we are on the cold side of the jet.

But with the warm air sitting there, it's got energy,

it wants to shift

but it's surrounded, it's flanked by pools of dense cold air

and with the jet stream not moving across it, there's very

little to shift it.

When we've got those blocked patterns,

the computer models always struggle.

Add into the mix a hurricane, yes,

a hurricane in January in the Atlantic.

And things are only going to get more complicated.

It's very unusual to see a hurricane and this time of year,

only four have been recorded in history,

records going back 150 years.

The storm system moves northwards, interacts

and adds energy to that warm air in the middle of the Atlantic,

adding confusion to the computer models

and therefore the forecast as we go into next week.

Hopefully we'll know more in the next day or two.