Major flooding could threaten parts of Sydney with drivers warned to avoid non-essential travel as a deadly storm brings intense rainfall along the eastern seaboard.

An inland low and coastal trough joining forces over New South Wales is forecast to bring heavy localised falls to much of the state on Friday.

Authorities warned 24-hour totals could top 200mm in Sydney and the south coast, with as much as 300mm dumped on the Illawarra Escarpment overlooking Wollongong.

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Major flooding was possible along the Hawkesbury Nepean River bounding Sydney from late Friday, with Penrith likely to cop as much rain in a day as one-and-a-half Aprils.

Transport for NSW took the rare step of warning drivers statewide to avoid non-essential travel.

“For those who need to travel, please take your time and plan ahead by checking Live Traffic NSW to see if your route is impacted by severe weather,” a spokeswoman said.

The storm has already claimed a life in Queensland after the body of a man was found by his ute near Logan, while a 30-minute wave of rain in northern NSW flooded enclosures at a wildlife sanctuary on Thursday.

“Due to the amount of water dumped into the park, we have relocated our animals and the hospital [has been] relocated to a higher position,” the Byron Bay Wildlife Sanctuary said.

With the catastrophic 2022 Northern Rivers floods fresh in minds, the SES said the silver lining for Friday’s system was that it was moving.

“If we go back to those northern river floods, it didn’t move as forecast,” the NSW SES commissioner, Carlene York, said.

“It stayed there, it kept dumping the rain and that’s obviously had the big impact.”

Volunteers had proactively deployed vehicles and vessels into danger areas.

Residents in such areas should clear gutters and tie down loose items ahead of time, SES metro zone commander Allison Flaxman said.

She urged them to download the official Hazards Near Me app to stay abreast of latest warnings.

“The forecasts are quite severe,” she said on Thursday afternoon.

“We don’t want anybody underestimating the impacts this could have on you.”

The weather bureau said catchments were fairly wet in the north and average to dry around Sydney and the south coast.

But the prospect of water releases down the Hawkesbury Neapan River mean Australia’s largest urban water supply dam threatens to spill.

Warragamba Dam, on Sydney’s south-western fringe, sat at 96% capacity as Friday’s storm approached.

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