Suburbs on Sydney’s fringes are facing the threat of significant flooding over the weekend as intense storms slowly shift south.

More than a month’s worth of rain fell over Sydney, Port Macquarie and Taree on Friday, delaying trains, cutting power and leading to evacuation alerts.

The severe weather risk, which has been caused by an inland low and coastal trough joining forces over New South Wales, was expected to have moved south of the capital by sunrise on Saturday.

But the Bureau of Meteorology warned isolated severe thunderstorms may redevelop on Saturday afternoon.

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Up to 150mm remained possible within a six-hour period for areas stretching from the Blue Mountains hundreds of kilometres to Narooma on the south coast.

Prepare-to-evacuate orders were issued on Friday night for parts of the Hawkesbury, as well as Narrabeen on the northern beaches, Camden in the south-west and Warwick Farm racecourse.

An evacuation order was meanwhile issued for low-lying Chipping Norton in the heart of western Sydney, for midnight on Saturday onwards.

Numerous rivers – including the Hawkesbury, Nepean, Georges, Lower Hunter, Myall, Macquarie and Woronora – were on flood watch.

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“With the forecast rainfall, further river level rises and moderate to major flooding is possible from Saturday morning along the Hawkesbury and Nepean Rivers,” the Bureau of Meteorology warned on Friday evening.

Liverpool and Milperra in southern Sydney could experience moderate flooding from the Georges River from Saturday morning.

Surfers and other beachgoers were also warned to stay “well away from the surf and surf-exposed areas” due to dangerous conditions, particularly at east-facing beaches.

Scores of community sport teams had their winter seasons delayed with flooded grounds from Wollondilly to the Northern Beaches closed all weekend.

No relief is in sight for Nepean and Hawkesbury communities downstream of Warragamba Dam with the reservoir holding most of Sydney’s water supply expected to spill from Monday.

The state premier, Chris Minns, advised residents to remain alert and up-to-date with warnings in their local areas.

“It is a volatile event and we need to make sure that we’ve got the latest information ... but it does require everybody being alert,” he said on Friday.

Laura Boekel, senior meteorologist at the Bureau of Meteorology, said intense rainfall will also continue over the weekend in parts of south and south-east Queensland, Boekel said.

“For parts of the southern and southeastern interior, widespread showers and thunderstorms will continue today and into tomorrow,” she said.

“Localised heavy falls could occur over the weekend and the area where we’re likely to see the most risk is the area south of Brisbane [on] Logan, Gold Coast and the Scenic Rim areas.”

A major flood warning is current for Charleville’s Warrego River in the state’s south west. River levels are expected to rise above moderate levels on Friday evening after several days of heavy thunderstorms.

A flood watch alert is in place for the Macintyre, Weir, Moonie and Balonne rivers.

Rainfall is expected to ease later in the weekend and next week, Boekel said.

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