16/09/2016 Weather for the Week Ahead

Hi there. Halfway through the month,

and so far September has had a bit of an identity crisis.

I'm sure you'll agree it's felt a bit more like July than September.

However, over the next few days, it's going to rediscover itself.

We can wave goodbye to these sorts of values,

which we saw on Thursday, nudging 30 degrees in some places.

And, yes, we're back to reality with a bump. Mid to high teens.

Mind you, that's more or less where we should be for the time of year.

We're replacing the sunny skies with some thundery downpours, too,

a real shock to the system, with some torrential rain in some places.

And the reason for that is a huge, great dig in the jet stream,

and where the jet scoops itself up across the country like that,

it tends to suck up the air into big, big thunderclouds,

and that's exactly what we've got at the moment,

some really shocking conditions up and down the UK,

with the possibility of some flash flooding.

Check out your BBC local radio station through Friday morning,

particularly across central and eastern parts of the UK.

In stark contrast, out west completely different - bright

and breezy, just a few showers around.

Now, the culprit for the thundery breakdown is this area of low

pressure, and these weather fronts are never really getting away.

Actually, as we start the weekend,

those fronts could start to head back westwards again.

Not the thundery downpours, but some damp, dreary weather,

perhaps, across central and eastern parts of England. Disappointing.

Best of the brightness on Saturday will be further west.

And again, those temperatures back to normal,

mid to high teens typically.

Now, we say goodbye to that front, we say hello to another front,

coming in off the Atlantic on Sunday,

bringing some rain to Northern Ireland and Scotland,

whereas further south and east across the country,

after a chilly start it looks set to be a reasonable day again

with some sunshine, lightish winds and temperatures much of a muchness.

On into Monday, and those fronts head down towards the

south-east, but as weakening features, just showery rain, really.

Further north and west, it brightens up again before the next

front comes in off the Atlantic,

and that again will bring some rain initially to Northern Ireland

and Western Scotland during the course of the day on Tuesday.

The best of the brightness by then looks like being further

south and east, for England and Wales, where the winds will

be lightest and the temperatures will be highest.

But again, those sorts of temperatures, mid to high teens,

maybe 20 degrees in one or two places.

Well, what's this? Snowfall, yes,

an early autumn snowfall in Yellowstone National Park, because

across the northern hemisphere the days are getting shorter and shorter

and the Arctic in particular is getting colder and colder,

and lobes of cold air tracking down across Canada and into Greenland

and eventually into the Atlantic.

And where lobes of cold air meet lobes of warm air coming up

from the tropics, we get a clash of the air masses, and where the

air masses clash, we get a supercharging of the jet stream.

If you were watching me yesterday,

I was explaining how where you get those contrasting air masses,

the jet tends to get propelled at high velocity towards us.

And the main oomph of the jet stream as we go towards the end of

the week looks like being across more northern and western areas,

and that's where we'll see most of the rainfall.

However, the jet never really gets down towards the more

southern and eastern areas, where we still have

a reservoir of relative warmth across Continental Europe.

What does that mean as we end the week and we go into, well,

the winter half of the year, shall we say?

One thing's for sure, the nights will get longer than the days,

back to normal weather-wise with that Atlantic influence,

wettest across the north-west but always that hint that we

could see some warmth at times

across the south-east. I'll update you again tomorrow.