GALE force winds with heavy rain are due to hit southern Australia on Wednesday, with a strong developing low pressure system prompting the Bureau of Meteorology to issue a severe weather update.

BoM meteorologist Andrea Peace said gale force wind warnings have been issued for the coastal waters extending from Perth to Adelaide.

The western districts of South Australia is under a severe weather warning for damaging winds, with a flood watch for the Mount Lofty Ranges, Mid-North and Adelaide Metro areas for the rainfall between Wednesday and Friday.

Ms Peace said the bureau expected to see renewed and prolonged river rises with the additional rainfall this week.

“So we’ll really start to see that low develop overnight tonight and into Wednesday, with the strongest winds on the western side of the low, but we will also see gusty northerlies ahead of this frontal system.

“We may also see thunderstorms develop, with lots of moisture streaming in ahead of this system,” she said.

“During Wednesday and overnight into Thursday we’ll see the low intensify further and we may see storm-force winds impacting parts of the central coast of South Australia.”

Large seas of 8-10 metres are also likely through the central SA coastal region, she said.

“Thursday will be quite a wet day for the eastern States as well, ahead of this frontal system.

“It will move towards the east as the low contracts eastwards also, but we’ll see more moisture wrapping in around the western side of the low during Friday.”

Thunderstorms are expected in eastern parts of South Australia during Wednesday and impacting the western parts of New South Wales and Victoria later on Wednesday, with falls of up to 20-40 mm, Ms Peace said.

“Through Thursday, widespread rainfall—20 to 40 mm through the eastern states—but, we could see some higher falls, particularly about the New South Wales Ranges and northeast Ranges of Victoria, and also some higher falls down in Tasmania as well.”

Severe weather across the six states and territories

Weatherzone meterologist Ben Domensino said the complex low pressure system and cold front will cause heavy rain, severe thunderstorms, destructive winds and heavy snow in multiple states.

“It is likely to be one of the biggest weather systems we have seen so far this year.”

He said by Thursday and Friday, the system’s impact will be widespread and could involve severe weather across the six states and territories, but the low should move into the Tasman on Saturday allowing calmer weather to return on the weekend.

“A very cold pool of air moving north from Antarctica is responsible for this volatile system.

“The frigid air will also help produce a hefty late-season snowfall, with the alps possibly in line for 30cm or more between Thursday and Saturday.”

He said the implications of the system across multiple states would include:

– Wind gusts capable of causing widespread structural damage and power outages

– Thunderstorms generating tens of thousands of lightning strikes across a three-day period

– Rain falling into already inundated rivers and potentially causing further flooding

– Storms potentially causing flash flooding and damaging winds

– Australia’s alpine region receiving an impressive late-season dump of snow.

Sources: Bureau of Meteorology, Weatherzone.