0:00:03 > 0:00:05Hi there. Halfway through the month,
0:00:05 > 0:00:07and so far September has had a bit of an identity crisis.
0:00:07 > 0:00:10I'm sure you'll agree it's felt a bit more like July than September.
0:00:10 > 0:00:13However, over the next few days, it's going to rediscover itself.
0:00:13 > 0:00:16We can wave goodbye to these sorts of values,
0:00:16 > 0:00:19which we saw on Thursday, nudging 30 degrees in some places.
0:00:19 > 0:00:23And, yes, we're back to reality with a bump. Mid to high teens.
0:00:23 > 0:00:26Mind you, that's more or less where we should be for the time of year.
0:00:26 > 0:00:30We're replacing the sunny skies with some thundery downpours, too,
0:00:30 > 0:00:33a real shock to the system, with some torrential rain in some places.
0:00:33 > 0:00:37And the reason for that is a huge, great dig in the jet stream,
0:00:37 > 0:00:41and where the jet scoops itself up across the country like that,
0:00:41 > 0:00:44it tends to suck up the air into big, big thunderclouds,
0:00:44 > 0:00:46and that's exactly what we've got at the moment,
0:00:46 > 0:00:49some really shocking conditions up and down the UK,
0:00:49 > 0:00:51with the possibility of some flash flooding.
0:00:51 > 0:00:55Check out your BBC local radio station through Friday morning,
0:00:55 > 0:00:58particularly across central and eastern parts of the UK.
0:00:58 > 0:01:01In stark contrast, out west completely different - bright
0:01:01 > 0:01:04and breezy, just a few showers around.
0:01:04 > 0:01:07Now, the culprit for the thundery breakdown is this area of low
0:01:07 > 0:01:11pressure, and these weather fronts are never really getting away.
0:01:11 > 0:01:12Actually, as we start the weekend,
0:01:12 > 0:01:14those fronts could start to head back westwards again.
0:01:14 > 0:01:17Not the thundery downpours, but some damp, dreary weather,
0:01:17 > 0:01:20perhaps, across central and eastern parts of England. Disappointing.
0:01:20 > 0:01:23Best of the brightness on Saturday will be further west.
0:01:23 > 0:01:26And again, those temperatures back to normal,
0:01:26 > 0:01:27mid to high teens typically.
0:01:27 > 0:01:31Now, we say goodbye to that front, we say hello to another front,
0:01:31 > 0:01:33coming in off the Atlantic on Sunday,
0:01:33 > 0:01:36bringing some rain to Northern Ireland and Scotland,
0:01:36 > 0:01:38whereas further south and east across the country,
0:01:38 > 0:01:41after a chilly start it looks set to be a reasonable day again
0:01:41 > 0:01:46with some sunshine, lightish winds and temperatures much of a muchness.
0:01:46 > 0:01:49On into Monday, and those fronts head down towards the
0:01:49 > 0:01:52south-east, but as weakening features, just showery rain, really.
0:01:52 > 0:01:55Further north and west, it brightens up again before the next
0:01:55 > 0:01:57front comes in off the Atlantic,
0:01:57 > 0:02:00and that again will bring some rain initially to Northern Ireland
0:02:00 > 0:02:03and Western Scotland during the course of the day on Tuesday.
0:02:03 > 0:02:06The best of the brightness by then looks like being further
0:02:06 > 0:02:08south and east, for England and Wales, where the winds will
0:02:08 > 0:02:11be lightest and the temperatures will be highest.
0:02:11 > 0:02:14But again, those sorts of temperatures, mid to high teens,
0:02:14 > 0:02:16maybe 20 degrees in one or two places.
0:02:16 > 0:02:18Well, what's this? Snowfall, yes,
0:02:18 > 0:02:22an early autumn snowfall in Yellowstone National Park, because
0:02:22 > 0:02:26across the northern hemisphere the days are getting shorter and shorter
0:02:26 > 0:02:29and the Arctic in particular is getting colder and colder,
0:02:29 > 0:02:33and lobes of cold air tracking down across Canada and into Greenland
0:02:33 > 0:02:35and eventually into the Atlantic.
0:02:35 > 0:02:39And where lobes of cold air meet lobes of warm air coming up
0:02:39 > 0:02:43from the tropics, we get a clash of the air masses, and where the
0:02:43 > 0:02:46air masses clash, we get a supercharging of the jet stream.
0:02:46 > 0:02:48If you were watching me yesterday,
0:02:48 > 0:02:52I was explaining how where you get those contrasting air masses,
0:02:52 > 0:02:55the jet tends to get propelled at high velocity towards us.
0:02:55 > 0:02:58And the main oomph of the jet stream as we go towards the end of
0:02:58 > 0:03:00the week looks like being across more northern and western areas,
0:03:00 > 0:03:02and that's where we'll see most of the rainfall.
0:03:02 > 0:03:05However, the jet never really gets down towards the more
0:03:05 > 0:03:07southern and eastern areas, where we still have
0:03:07 > 0:03:11a reservoir of relative warmth across Continental Europe.
0:03:11 > 0:03:15What does that mean as we end the week and we go into, well,
0:03:15 > 0:03:18the winter half of the year, shall we say?
0:03:18 > 0:03:20One thing's for sure, the nights will get longer than the days,
0:03:20 > 0:03:23back to normal weather-wise with that Atlantic influence,
0:03:23 > 0:03:27wettest across the north-west but always that hint that we
0:03:27 > 0:03:28could see some warmth at times
0:03:28 > 0:03:30across the south-east. I'll update you again tomorrow.