Weather update: Widespread rain this week for the south and east

Widespread rain on the way for southern and eastern Australia this week. I’m Angus here at the bureau. Today’s Wednesday. This is a weather update ahead of the extensive wet weather, which will pack quite a punch and have a number of impacts, including riverine rises.

That rain falls, it fills up the rivers, they climb and potentially burst their banks, which leads to flooding down the river system. That looks most likely to occur in Victoria on Friday and Saturday, but may happen in parts of neighbouring states. We’ll see a lot of rain across agricultural areas. In some places that will be welcome. Rain into growing regions can be a very good thing, but it can also be too much of a good thing if you get too much rain, leading to waterlogged pastures and closed roads.

We will see thunderstorms, particularly across South Australia, leading to smaller pockets of more intense weather, with even heavier rain, damaging wind and large hailstones.

Now a Flood Watch has just been issued across Victoria. A Flood Watch is basically a heads-up along these river networks that we might see the water levels rise and these rivers could see the water levels burst their banks, leading to flooding downstream of where the rain falls. The Watch at the moment includes most rivers through northern Victoria, as well as rivers down through parts of Gippsland and even eastern parts of Melbourne. So a lot of rivers included in this Watch. We might see more rivers added over the coming days, and we might see some of these watch areas get upgraded into warning areas.

Once we start to track that rain falling and see how the rivers are responding, let’s look at some of the data that’s being the key map really, when it comes to data. This is the rainfall accumulation map. This is all the rain we expect between today, Wednesday and the end of the weekend, Sunday night.

In particular for this map, take a look at the areas which are orange and then pushing in towards red. That’s where we expect the larger accumulations of rain. There is a smattering of that out over the outback of Western Australia, but in terms of areas where more people will notice the rainfall, we’re really looking at the south-east of the country. This is a key area for the upcoming wet conditions.

The forecast is for some fairly extensive rain around central and eastern parts of Victoria, from Melbourne out to Gippsland, where we could see widespread 50 mm to 100 mm over the rest of this week and weekend, some places pushing beyond that into the triple figures, where particularly exposed parts of Gippsland could see between 100 mm to 150 mm.

The rainfall across southern New South Wales may not be quite as heavy as Victoria, but significant accumulations are forecast for the Snowy Mountains, the Snowy Valleys, ACT, the Southern Tablelands and perhaps the south-east coast, 30 mm to 60 mm across a broad area here, with isolated places, particularly in the mountains, seeing more.

Rainfall in South Australia, it will be a little lower than in its neighbouring states, but 10 mm to 20 mm, perhaps 30 mm in places through from Adelaide across to the Murraylands, Riverland and the south-east.

And then for Tasmania, western parts will get a healthy dose of rain, perhaps 30 mm to 50 mm. At the moment, the forecast is for lower amounts on the east coast, including Hobart, but this is certainly an area to watch as that forecast could get ramped up in the next few days.

Tomorrow, Thursday, thunderstorms will play a significant role in South Australia in particular. The yellow region shows where we’re flagging a risk of severe storms with heavy rain, damaging wind and large hail, and the risk of storms also extends down towards Adelaide and even across the border and through most of Victoria.

Now that’s the fine print. That’s the detail. Let’s zoom out a little bit and see what’s causing all this rainfall. It’s actually a collection of a couple of different weather systems. This dashed blue trough line with plenty of moisture lies between Tasmania and Western Australia today, but there’s a couple of weather features to the south-west of that rapidly approaching.

And on Thursday, those three weather features are all going to bunch up together and ram into one another. And when that happens, they merge into one and we see the associated band of rainfall gets broader and heavier across South Australia and Victoria. So the rain really starts to ramp up on Thursday.

But that’s not the end of the story, because on Friday we’ll see a low pressure area developing here somewhere near the New South Wales-Victoria border. And whenever a low develops in a band of rain exactly like this, it tends to slow down the progression of the entire weather system. So rather than whipping off the coast quickly, it stays stuck in the mud. We see rainfall over a prolonged period of time, continuing to dump wet weather on Victoria, southern and interior New South Wales and parts of south-east SA.

During the weekend this low will eventually make its departure. Moving off the south coast of Victoria on Saturday could be a bit of a sting in the tail too, for the likes of the Otway coast or maybe the Gippsland coast, and then moving past Victoria, moving past Tasmania on Sunday, maybe a final flourish for parts of Tasmania with weather there to round out the weekend.

We will see most of those conditions clear up as we head into the start of the new week with much brighter weather. Plenty of rain in the next few days.

Do stay up to date with your local forecast on the bureau’s website or app, and we’ll keep updating you on our social media channels too. Thanks for watching.