A spell of warm and sunny weather across south-eastern Australia is forecast to come to a shuddering halt this week.

Tasmania, Victoria and southern NSW will feel much chillier by Thursday when a blast of cold winds from the deep Southern Ocean rolls in, reports weather data firm Weatherzone.

The weather system will begin its march on Wednesday, and over the following 24 hours, snowfalls can be expected in parts of the NSW Snowy Mountains, the Victorian Alps and the Tasmanian Highlands.

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The latter two could record falls as low as 800 metres, forecasters say.

A second cold front is due to arrive early Friday, extending the plummeting temperatures and gusty winds through the day, while snowfalls will be limited to higher ground.

But skiers and snowboarders shouldn't expect an early start to the winter sports season.

"Snow accumulations across the two days should amount to approximately 10-20cm across the Victorian and New South Wales major resorts and about 3-8cm across the Tasmanian Central Plateau and the higher peaks in south-west Victoria," according to Weatherzone.

"This should be ample snow cover for snow play, snowball fights and maybe a slide on a toboggan."

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Residents in south-eastern capital cities should be reaching for the winter woollies by Thursday when the mercury drops markedly.

Canberra is heading for a chilly maximum temperature of 8 degrees, Hobart 11 degrees, Melbourne 12 degrees, while Sydney can expect a far more pleasant 19 degrees.

Anyone heading outdoors should prepare to add an extra layer of clothing, with cold, gusty winds accentuating the chill factor.

The wintry blast is forecast to be brief, with seasonal average temperatures returning by the late weekend.

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US President Donald Trump says the Pentagon is preparing to release some "very interesting" UFO files uncovered by his administration, generating a mix of buzz and scepticism as he hints at new revelations around questions of alien life.

Trump started stoking interest in February, directing federal agencies to release their records related to extraterrestrial life and UFOs. Since then, he has built suspense with tantalising updates, teasing an imminent release of documents never before shared by the US government.

"We're going to be releasing a lot of things that we haven't," Trump said on Wednesday at a White House event celebrating NASA astronauts.

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"I think some of it's going to be very interesting to people."

Trump has relished in portraying himself as the president who spills the secrets. In the first week returning to office, he ordered the release of records related to the assassinations of President John F Kennedy, Senator Robert F Kennedy and Martin Luther King Jr. The disclosures revealed little beyond what was already known.

In the buildup to that release, Trump said "the American people deserve transparency and truth".

Now, as he turns to the sky, the president has struck a similar tone, suggesting answers to decades-old questions may be on the way.

His February directive on social media called for transparency around "alien and extraterrestrial life, unidentified aerial phenomena (UAP), and unidentified flying objects (UFOs)".

"The first releases will begin very, very soon," he told supporters in April at a Turning Point USA event in Phoenix.

"So you can go out and see if that phenomena is correct. You'll figure it out."

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Expert cautions against raising expectations

Even before Trump's directive, the Pentagon was years into a process to declassify and release government documents related to UFOs, now often referred to as unexplained anomalous phenomena, or UAP.

Citing concerns over national security, Congress created an office in 2022 to investigate UAP and declassify as much material as possible. The office's 2024 debut report revealed hundreds of new UAP incidents but found no evidence that the US government had ever confirmed a sighting of alien technology. A second report covering more recent sightings is expected to come soon.

That agency, the All-domain Anomaly Resolution Office, is now working with the White House to release "never-before-seen UAP information", according to a Pentagon statement.

The office's previous director, however, said Trump's promises were bluster, a "shiny object" to distract Americans from the war with Iran. Sean Kirkpatrick, a physicist and former career intelligence officer who led the office until 2023, said he has seen the government's records and believes there are no bombshell revelations to be found.

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"Readers should not get their hopes up that there's going to be some document with photos, interviewing the aliens when they came down," he said. "Because that just doesn't exist."

Videos purporting to show alien technology tend to have mundane explanations, he said. Modern infrared cameras used by the US military often capture jet engines and other hot objects in a long thermal bloom, which, Kirkpatrick said, explains viral videos of speedy, pill-shaped objects.

Pentagon not forthcoming on UAP reports, GOP-led panel says

On Capitol Hill, those types of videos have caught the attention of a small group of Trump-aligned Republicans who insist the Pentagon is holding back secrets.

The Task Force on the Declassification of Federal Secrets has been conducting its own investigation into reports of mysterious aircraft near US military installations, which the panel says pose a threat to national security and the armed forces.

Last autumn, the task force heard testimony from current and former service members who described UAP encounters. In one case, a senior Navy officer said he was off the coast of California in 2023 when he saw a glowing "Tic Tac" shaped object emerge from the ocean and link up with three similar objects. They sped away in an instant, he said.

Trump's interest in the subject has energized congressional Republicans, including Florida Representative Anna Paulina Luna, an Air Force veteran who co-chairs the task force. Luna has criticised what she calls "more than adequate" transparency from the Pentagon.

In a March letter to Defence Secretary Pete Hegseth, Luna demanded dozens of UAP videos identified by whistleblowers and labelled with names such as "Spherical UAP in clouds". Her deadline for Hegseth came and went, and no videos were produced.

Trump's entry to the UFO fray drew applause from Luna, who last year told podcaster Joe Rogan that she has seen evidence of "interdimensional beings." The Pentagon "can't hide from our docs request anymore!" Luna said on social media after Trump's directive.

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One Nation has its eyes on success in the seat of Nepean ahead of the November state election, despite the Victorian Liberal Party gliding to victory in yesterday's byelection.

Liberal candidate Anthony Marsh rose to the top of the ballot on the Mornington Peninsula yesterday but suffered a haircut on the primary vote, with One Nation candidate Darren Hercus picking up one in four first-preference votes.

The former Mornington Shire Council Mayor succeeds former deputy Liberal leader and ex-pro tennis player Sam Groth, who retired from politics in February.

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With almost 80 per cent of the vote now counted, Marsh has picked up 38.5 per cent of the first preference vote.

That represents an almost 10 per cent slump in first preference support for the Liberals compared with the last election.

Most of those votes went to One Nation candidate Darren Hercus and Independent Tracee Hutchison, who each saw first preference swings of more than 20 per cent towards them.

But it wasn't enough to tip the Liberals from the seat, who led by more than 10,000 votes once preferences were distributed.

"It is the honour of my life to be standing here in front of you as the next member for Nepean," Marsh told Liberal Party supporters after a clear result was declared around 9pm.

"It's been a hard-fought campaign, I think we're day 67 in and to stand in a room full of blue after what was an incredible day, I am so honoured and privileged again to be in this role."

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The by-election had been regarded as Wilson's first test ahead of the state election in November.

"I say thank you to the residents down here on the peninsula for putting your trust in Anthony and in me," Wilson told supporters last night.

"I will not let you down, I will fight for you every day.

"I have met thousands of you over the past few weeks. I have looked you in the eye and I have said 'as your next premier, I will deliver for you'."

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The by-election was also touted as a major litmus test for One Nation, which has gained a large groundswell of voter support in the last six months owing to a strong appetite for change.

Pauline Hanson is yet to comment on last night's performance, but data shows around one in four Nepean voters put One Nation first on their ballot yesterday.

There'll be no break from campaigning, with Hercus and Hutchison both vowing to contest the seat when voters return to the polls for the state election.

"Twenty-four, 25 per cent, that's huge," Hercus said.

"It's a big swing. The Liberal Party have done well but we're in the game now. We're a serious contender."

Marsh said elections were a competition.

"I take nothing for granted, I'll fight each and every day between now and November," Marsh said.

Federal counterparts in Farrer were watching the vote closely ahead of their own by-election next weekend.

Speaking to Weekend Today, former Nationals leader David Littleproud said it was difficult to draw comparisons from the strong Liberal result in Nepean.

"It will be a challenge, I think federal and state issues are different," Littleproud said of the Farrer by-election.

"By-elections send very different messages to general elections, but every election sends a very strong message for everyone to learn from, as it was for the Liberals in this state seat as well."

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A mother, father and their adult son have been killed in what police allege was a gruesome triple murder in Sydney's south-west.

Charles Feng and Ruvena Lam's oldest son, Jacky Feng, who was arrested outside their Rosemeadow home, has been charged with murdering his parents and youngest brother and trying to kill another brother.

Senior police said officers were confronted with a "very grizzly crime scene".

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At 1.30am today officers found 65-year-old mother Ruvena Lam injured and started CPR before discovering the full scale of the tragedy on Juliet Close.

"Police then went inside the house, and found a 64-year-old male who was still alive with serious blunt force head injuries," Superintendent Grant Healey said.

That man was 64-year-old Charles Feng.

Neither he nor his wife survived.

Police then found their youngest son, 25-year-old Justin, dead in the granny flat.

"This is an incredibly rare incident and it is incredibly tragic," Healey said.

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A third brother, aged 30, was injured but was able to call Triple Zero.

He is out of hospital but unable to go home.

Police alleged the 32-year-old accused left the scene this morning before officers arrived but came back an hour later and was arrested.

He was charged this afternoon with three counts of three counts of murder (DV) and one of attempted murder (DV) and refused bail to appear before Campbelltown Local Court tomorrow.

Forensics are still searching for multiple alleged murder weapons including a hammer.

They towed away the suspect's car, as they hunted for a motive.

Healey said emergency services were faced with a "horrendous" scene.

"They were confronted with a very bloody scene," he said.

He said the family was not well known to police and never for domestic violence incidents.

"This is a very tragic incident, there was no way for us to predict this kind of thing to occur," he said.

Support is available from the National Sexual Assault, Domestic and Family Violence Counselling Service at 1800RESPECT (1800 737 732)

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Search and Rescue teams have been called to the Masterton river.

Dashcam video shows riders running red lights and mounting the footpath.

Police have revealed jaw dropping footage of rioters looting a service station amid unrest in Alice Springs.

Five people have been arrested over the riotous behaviour, which started over the alleged murder of five-year-old girl Kumanjayi Little Baby.

Jefferson Lewis has now been charged.

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Police say the service station on Bagot Street, The Gap, as well as a supermarket on Gap Road were targeted by rioters on Thursday night.

Footage shows one man opening what appears to be a locked door of the service station.

Dozens of people pour in and start grabbing items from the shelves.

Some then start tossing shelving over in the packed shop.

The service station is directly opposite Alice Springs hospital.

The burglary happened on the night of Thursday's riot, sparked after Lewis was allegedly hunted down and beaten in what detectives said was vigilante retaliation.

"What you will see is criminal behaviour plain and simple," NT Police Commissioner Martin Dole said.

Police say about $105,000 worth of property was stolen and $80,000 of damage was caused.

Five people – aged 18, 26, 34, 46 and 49 – have been arrested and are expected to be charged.

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Police say more arrests are expected.

Lewis was today charged with one count of murder after the death of five-year-old Kumanjayi Little Baby.

A large crowd assembled outside of Alice Springs Hospital on Thursday, with a car allegedly being set on fire, as well as reports of paramedics and police being assaulted.

Surfers are being trained to use shark-spotting drones as part of a new plan to keep our beaches safe all year.

The drone program is being launched in tribute to boardrider Mercury Psillakis, who was killed in a shark attack at Dee Why on Sydney's Northern Beaches in September.

For the Psillakis family, the tragedy of a fatal shark attack remains very raw.

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But their grief is tempered by the new program, with each drone carrying the 57-year-old's name.

"He'd be proud that he's somewhat responsible for extra safety on our beaches," wife Maria said.

"He'd probably cry, knowing Merc."

The experienced surfer was fatally bitten by a white shark.

His brother Michael thinks drones could have saved him.

"If there was a drone in the sky that day, my brother would still be with us," he said.

But it won't be just one; 60 drones are being rolled out from Newcastle to Wollongong.

"The government is trying to embrace new technology and new ways of monitoring for sharks and keeping people safe on our beaches," Agriculture Minister Tara Moriarty said.

But unlike those operated by surf life savers only when patrolling, these will be flown by boardrider clubs during carnivals and training sessions 365 days a year.

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Ben Wheeler from Mona Vale Boar riders is one of 125 now undergoing drone pilot training.

"I think having that early warning, as was said earlier, is amazing, you know just to keep our members safe in the water," he said.

The drone program will cost $650,000 out of a $30 million shark safety budget.

"We saw activity from bull sharks over the summer and now we're heading into a period where we'll see more white sharks on our beaches and waterways, so I'd encourage people to download the Shark Smart app," Moriarty said.

That app tracks in real time sharks that have been tagged, alerting surfers to any activity on their local beach.

While these require a pilot to fly, the next generation of fully automated drones with AI technology able to identify sharks and shark species and able to fly from dawn until dusk is already being considered.

It's the legacy of a hero surfer who in the face of an attack, tried to warn others.

"It's just upsetting he's not here to see it," Maria said.

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Prime Minister Anthony Albanese has warned the worst of the energy crisis may be ahead but won't guarantee an extension to fuel price relief.

Speaking with 9News on the first anniversary of his re-election, Albanese said an extension to the reduced fuel excise, which is due to expire in July, won't be detailed in next week's federal budget.

"That'll be decided further down the track, there are too many changes," he said.

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The reduced fuel excise has been saving motorists between 20 and 30 cents a litre since the fuel crisis started in February.

Despite grappling with a strained fuel supply for nearly 10 weeks, Albanese couldn't indicate whether the worst of the fuel crisis was in the past.

"In terms of petrol, are we through the worst of it now, or is there still worse to come?" 9News chief political editor Charles Croucher asked.

"There's real uncertainty there," Albanese responded.

Croucher said: "It will worry people that the answer isn't definitively that the worst is behind us."

Albanese responded: "It's because it's an unpredictable world, and I think people understand there's no certainty here."

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With uncertainty surrounding the war, the prime minister seems sharply focused on sourcing cost-of-living relief elsewhere.

Tax cuts are already legislated for every taxpayer and will begin in July, right as the fuel excise is due to end.

Next week's budget will focus on changes to the capital gains tax discount and potentially negative gearing and trust tax arrangements.

The government says that will make things fairer for future generations.

"One thing young people say to me, but also their parents and grandparents, particularly grandparents, is that they worry about their grandkids," Albanese said.

Assistant Treasurer Daniel Mulino also addressed the issue.

"I think the Australian people would hope that we would look at tax in the context of these broader themes of intergenerational fairness and productivity," he said.

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But One Nation and the Liberal Party say the tax changes represent broken promises, arguing they weren't flagged in Labor's election campaign a year ago.

"If you want to create more of something – in this case housing – the answer isn't taxing it," Liberal Senator Claire Chandler said.

One Nation member Barnaby Joyce said the government should be "encouraging people to be prudent because the more they put away the less we have to look after them in old age".

"Because if I've got a choice between giving it to Jimmy or spending it myself – I suppose I'll just spend it," he said.

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The judge called the case ‘very unique and unusual’ for such an unsavoury-sounding charge.