Ferocious storms, giant hail and wind gusts in excess of 125km/h are expected in multiple states, with destructive weather expected to hit much of the east coast.
A cold front colliding with a warm and humid northerly airstream is delivering prime conditions for wild storms.
Severe weather, hail and some flash flooding hit parts of South Australua overnight, with wind gusts of more than 130km/h recorded at Port Pirie and Roxby Downs, and a 36mm deluge in one hour reported at Mount Horrocks.
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“The risk of thunderstorms will be widespread in the east, from southern Queensland through NSW, Victoria and into northern Tasmania.” senior Bureau of Meteorology forecaster Miriam Bradbury said in an update.
There was also a risk of storms in parts of inland Queensland and the Northern Territory, but these were unlikely to bring much rainfall, she said.
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Severe storms were most likely across NSW’s central and southwest slopes, and in northeast Victoria.
“In these areas, we may see locally destructive winds … in excess of 125km/h, (and) we might also see giant sized hail or intense rainfall,” Ms Bradbury said.
“These storm hazards may lead to downed trees or branches, power outages, dangerous driving conditions with water or debris over roads, localised flash flooding and some property damage due to winds
Casterton, in Victoria’s west, was struck on Wednesday afternoon by what some locals called worst storm they had encountered.
“Everyone is in shock by the sheer ferocity of it,” Heidi Herbert from Herbert’s Bakery said.
“I’ve never heard a noise like it before. It was like a freight train but worse … I stood outside on the verandah and it was just deafening.
“We saw the clouds come in and the thunder and lightening but had no idea this was coming. It all happened so quickly, it caught everyone by surprise.”
The bureau said Casterton copped a 20 to 25 minute bucketing which included strong winds, 5cm hail and flash flooding.
“There was heavy rainfall of about 22 mm in 20 minutes … that doesn’t sound like heaps of rain but when it falls in 20 minutes that’s significant,” Ms Bradbury said.
The State Emergency Service took more than 80 calls, 65 relating to building damage or flooding.
Flood watch warnings could be issued in the coming days, but the front itself is expected to move off the east coast early on Saturday, taking the most severe weather offshore.
“Southern Victoria, Tasmania and eastern NSW will see easing showers during Saturday, with gusty southerly winds,” Ms Bradbury said.
“At times, it will be a little cool through southern Victoria, but it will remain mild elsewhere.”
Crowds heading to the MotoGP at Phillip Island, southeast of Melbourne, have been told to reconsider travel plans.
“Try and hunker down, make sure you’re where you need to be by (Friday) morning or put your plans off through those high risk areas,” Victorian SES commander David Baker said.
There’s also an increased risk of thunderstorm asthma for northern parts of Victoria.
Southeast Queensland and northeast NSW may experience storms, but they were not expected to be severe.
The wild weather is expected to ease in eastern and southeastern Australia by Sunday, which is expected to be a mostly dry and relatively sunny close to the weekend.