Sydneysiders are on high alert for possible flash flooding and landslips, after the weather bureau issued a severe warning for heavy rainfall over the weekend.
A coastal trough forming off the NSW coast could mean some areas in the Sydney, Illawarra and Central Tablelands regions could experience a month's worth of rain in the coming days, the Bureau of Meteorology (BOM) said.
"We know these are quite dangerous systems and they've been known to produce some widespread flooding in the past and that's certainly on the cards for the next few days," meteorologist Jane Golding said.
Ms Golding said rain was likely to intensify on Saturday right through to Monday, which could lead to flash flooding, riverine flooding and landslips.
There is minor to moderate flood warnings in place for parts of the Hunter, Central Coast, Greater Sydney and South Coast, with major flooding possible in the Hawkesbury Nepean Valley.
"What our hydrologists are seeing is the rain is potentially enough to cause major flooding there again, which will be the third or fourth time in the last two years for those communities," Ms Golding said.
The State Emergency Service (SES) is ramping up their communications with the addition of extra staff in its call centres.
NSW SES Commissioner Carlene York urged residents in areas prone to getting cut off by flooding to have emergency food supply ready, as well as a radio with batteries in case of a telecommunication outage.
"I don't want people to be complacent, because their house or business has not been affected in the past doesn't mean that it might not be affected through these forecast rain events," Ms York said.
She advised residents to stay up-to-date with information on the SES website and to take heed of warnings issued over the coming days.
"If we give an evacuation order, please evacuate and evacuate quickly because I can't always have an SES vehicle or our partner agencies able to access.
"Roads get cut off very quickly. It's dangerous out there in the weather and we want to make sure that you make those decisions very early.
"Because you will place yourselves at risk and you will place my volunteers and emergency services at risk as well."
