Parts of the New South Wales coast are bracing for dangerous swells and strong winds this weekend, as residents in coastal WA batten down in the face of destructive Tropical Cyclone Narelle.

The Bureau of Meteorology has issued a hazardous surf warning for the Byron, Coffs, Macquarie, Hunter, Sydney, Illawarra, Batemans  and Eden coasts on Saturday.

It followed a similar alert issued for several coastal areas on Thursday and Friday that prompted NSW Police to warn that unpredictable surf would put anyone entering the water at risk.

“We’re urging anyone who planned to head out on the water this weekend to reconsider it,” said Detective Chief Inspector Anthony Brazzill from Marine Area Command.

“Strong winds and powerful surf are expected, which will put not only the public at risk but also emergency services.”

A Surf Life Saving NSW spokesperson told the Sydney Morning Herald the conditions would potentially be a “one-in-50 to one-in-100 year event”.

Transport for NSW said the forecast high swell would force the suspension of ferry services in Sydney, with no ferries expected to operate between Manly and Circular Quay until at least Sunday morning.

The Bureau of Meteorology is also forecasting blizzard conditions for alpine areas above 1900m on Friday, with damaging winds averaging 80 to 90km/h possible into the afternoon.

The first dusting of snow has fallen in the alpine areas of south-east Australia overnight, with a very cold air mass moving through. Some 10cm of snow fell overnight at Perisher, Australia’s largest ski resort, with 15cm at Thredbo.

Meanwhile, Tropical Cyclone Narelle has been barrelling down on WA’s north-west coast, unleashing gusts strong enough to shake buildings.

There were reports on Friday of roofs being torn off by “terrifying” wind gusts, boats being sunk and homes flooded by driving rain, as people in some areas were evacuated.

Narelle has intensified into a category four system producing gusts up to 260km/h, and approached WA after leaving a trail of damage across Queensland and the Northern Territory.

On Friday, the wild winds cut power, shook buildings and caused widespread damage in the resort town of Exmouth, 1250km north of Perth.

The roof was even ripped from the main evacuation centre, with about 50 people forced to move from the centre to a local church.

“The really destructive core passed just west of Exmouth, and it has been severely impacted,” Department and Fire and Emergency Services Commissioner Darren Klemm said on Friday.

“We’re expecting some pretty significant damage out of this.”

The system produced  “absolutely screaming winds” as it passed Exmouth, gateway to the Ningaloo Marine Park.

Exmouth Shire president Matthew Niikkula said roofs had lifted off houses and many others were flooded.

“Not a person in town would have got any sleep last night … screaming winds, lots of bangs, everyone’s house shaking, sitting in the dark with their candles or their torch,” he said.

“It’s a really, really terrifying experience.”

On Saturday, Narelle is expected to weaken as it moves south-east, triggering heavy rainfall that could lead to flash flooding and dangerous storm tides, the bureau warned.

While stormwatchers were keeping their eyes on the west tracking the cyclone’s path on Thursday night, New South Wales was slammed by storms that left several thousand people still without power on Friday.

The State Emergency Service recorded 400 incidents across NSW, including 46 in Dubbo, which was badly affected by severe thunderstorms.

Severe winds partially collapsed a crane on a building site in the central west NSW city.

The storm also caused chaos for commuters, with trains and Metro services cancelled, and emergency crews responded to multiple reports of fallen trees that damaged cars and tangled powerlines.

–with AAP