31/03/2016 Weather for the Week Ahead

I'll get onto the first week of weather in April in just a moment.

First of all, a quick look back at March,

because the provisional statistics are in.

Overall, it was a pretty average month.

Average sunshine, average rainfall and average temperatures.

But there were, as this map shows,

some significant regional variations.

This map showing the minimum temperatures

and, actually, the nights were pretty cold,

below average across the southern half of the UK,

whereas parts of northern Scotland were above average.

Now, most starting Thursday on a pretty chilly note.

A frost across parts of the UK.

And, again, it's a day of sunshine and showers.

The showers initially focused across south-east Scotland,

north-east England, hail and thunder is possible,

and becoming more widespread as the day goes on.

But they'll be fairly slow-moving.

Could be quite intense, but there won't be as many of them around

and parts of Northern Ireland, Wales,

south-west England, northern Scotland,

may well simply stay dry and sunny.

Overnight, again, the temperatures will be dropping sharply.

A colder night across the south on Thursday night and into Friday.

But not as cold in Northern Ireland,

because here we'll start to see a change.

A weather front arrives, the breeze picks up,

the cloud arrives, and then it turns wet.

A wet day for Northern Ireland and western Scotland.

The rain creeping into other parts of Scotland,

maybe north-west England, too.

For the bulk of England and Wales, Friday's a fine day.

Where the sun hangs on for longest, we could reach 14 Celsius.

The weather front looks like winning

and pushing rain across all parts into the weekend.

But hold on. It stops through Saturday

and start to pivot back as low pressure approaches,

anchoring itself to the west of the UK.

When those weather fronts do that,

there's always some uncertainty about the position.

It could be a bit further south or a bit further north.

But there'll be some rain across northern Britain on Saturday,

whereas many southern areas look dry

and, again, with some sunshine, reasonably warm.

It's turning warmer because the low anchored to the west

is allowing the winds to come up from the south-east,

drawing up some warm air from France.

When that happens, as well as turning warmer,

it also, potentially, brings the risk of heavy thundery showers.

A lot of uncertainty about the intensity

and where we see these downpours.

They could be tracking northwards during Saturday night

and into Sunday.

As they clear, again, with the warmer air,

temperatures, if we see some sunshine,

could easily get to 16 degrees or more.

Then into next week. Quite a bit of uncertainty, it has to be said.

All tied into the jet stream.

We've been watching John Hammond the last couple of days,

he's been talking about this change in position,

turning more straightforward, as you might imagine, from east to west.

But notice the jet stream's never that close to the UK

and it looks like it'll be relatively weak.

That's what happens at this time of year.

The jet stream is strongest through winter, and that's because

that's when you have the strongest temperature contrast.

In the winter months, the Arctic is bitterly cold.

It doesn't get any sunshine.

And there's a strong contrast

between the very cold air and the mild air.

It's that strong contrast that produces a strong jet stream.

Now, this time of year, into the spring months,

the Arctic is starting to warm up, we're beyond the equinox,

and so that contrast isn't as marked,

the jet stream isn't as strong.

That's why we tend to get more storms in the autumn and the winter.

Not saying there won't be any stormy weather

over the spring or summer months,

but that's one reason why the jet stream is a little lighter,

a little less intense.

It will, though, be influencing things next week.

The westerly winds will return.

After some brief warmth, the days will turn cooler.

There'll be some showers around.

The nights, though, should be a little milder.

Don't forget, we're talking about patterns here.

We'll firm up on the details next week.