The weather bureau has expanded its warnings for widespread heavy rain, isolated thunderstorms and damaging winds across south-eastern Australia.

Heavy rain, with six-hourly totals up to 50 millimetres, is forecast to begin in coming hours across central and northern Victoria, with the Bureau of Meteorology warning the risk zone also included Melbourne.

NSW and Tasmania are also in the firing line, with similar totals expected overnight in southern NSW. Tasmania can expect up to 100 millimetres late on Wednesday and into Thursday.

The forecast for Thursday across all three states is even more dire.

“On Thursday 24-hour rainfall totals of up to 120 millimetres are possible over elevated terrain in Victoria and may reach over 300 millimetres for parts of elevated Tasmania,” the Bureau of Meteorology said on Wednesday afternoon.

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Forecaster Weatherzone said earlier that Melbourne had 8 millimetres of rain by midday Wednesday.

“However, this is just a taste of what’s to come over the next 24 to 48 hours,” it warned.

Regional communities have been warned to prepare to be isolated for up to three days as the worst of the weather hits. In Victoria’s high country, Bogong Village was evacuated on Wednesday as a landslide cut the Bogong-High Plains Road.

The Bureau of Meteorology issued a severe weather warning for heavy rainfall on Thursday, covering most of Victoria.

“Widespread rain, combined with wet or already flooded catchments will lead to renewed river and creek rises, and moderate to major flooding is likely across northern and central Victoria, and northern Tasmania. Flood watches have been issued in both Victoria and Tasmania,” it said.

“Flash flooding may also become a risk, including for the Melbourne area on Thursday afternoon and evening.

“Heavy rain also increases the risk of landslips and debris across roads.”

Emergency services have been deployed to multiple regions in Victoria, including Wimmera in the west, and along the Avoca, Loddon and Campaspe rivers. Sandbags are also available at multiple sites across the state.

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Victoria’s Emergency Management Deputy Commissioner Chris Stephenson urged communities to prepare early.

“You need to make sure that you are prepared for up to 72 hours of potential isolation,” Mr Stephenson said on Tuesday.

Premier Daniel Andrews advised Victorians to be vigilant.

“We know that our catchments are full, we know that we’ve had record rainfall to this point, and the ground is absolutely sodden,” he said.

He also repeated warnings for motorists not to drive through floodwater – a warning repeated in NSW after the body of a man was found in his submerged car in the state’s central west on Tuesday.

The Bureau of Meteorology has also issued severe weather warnings for northern Tasmania and southern NSW.

In NSW, the Murrumbidgee River is one of those of most concern, with moderate flooding expected at Wagga Wagga on Wednesday night.

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In Tasmania, the warnings cover the north and central regions, and the east coast, which is tipped to be hit by dangerous winds.

Heavy rain is expected from Wednesday evening to Friday, with the north expected to cop the worst, including intense local falls.

The Tasmanian SES said widespread minor or moderate flooding was likely from Thursday and major flooding was possible at some locations.

“People are encouraged to be aware of the forecast and prepare their property before the rain arrives,” acting director Leon Smith said.

“This means knowing your flood risk and understanding whether your property is prone to flooding.

“With the ground being saturated in many areas of Tasmania, rivers will rise quickly over coming days.”

Mr Smith said the crisis looming for Tasmania appeared likely to be similar to flooding it last endured in 2016 – in which three people died.

-with AAP