NSW State Emergency Service specialist crews have been sent to the state's north and floodwaters in Gunnedah are set to exceed last weekend's major peak on Friday night, after widespread rain across the state.
After more than 150mm of rain fell on parts of the Northern Rivers in the space of two hours overnight, the NSW SES sent a text message to people in the Tweed, Ballina, Lismore and Byron areas warning of the possibility of flash flooding ahead of rapidly deteriorating conditions today.
"At approximately 3.00am this morning we made the decision to communicate to our residents of four LGA areas that with the heavy rainfall we're experiencing here in the northern rivers, that flash flooding is a very likely a possibility," SES Northern Zone's Scott McLennan said.
Mr McLennan said locals should be prepared to evacuate if necessary.
The NSW State Emergency Service conducted 14 flood rescues since Thursday morning, with over 190 calls for assistance.
The weather bureau has issued multiple flood warnings including a flood watch for the Northern Rivers, Mid North Coast and Hunter Districts.
"The challenges we've got is with the Tweed, along with the Wilson and the Bellinger, is the flash flooding situation with all this heavy rain falling in random spots we are starting to see some significant flash flooding situations occur," Mr McLennan said.
Heavy rain is also causing flooding further inland at Tamworth, Wee Waa, Wellington and Narromine.
The BOM has issued a renewed major flooding warning for the Namoi River at Gunnedah on Friday night, which is expected to be higher than the peak that moved through earlier this week.
Mr McLennan said the conditions would remain bad throughout the weekend as a low pressure system persisted over the area, meaning school holiday travellers should remain cautious and avoid driving through floodwaters.
"It's leaving in its wake a lot of water and a lot of trees down and there are some landslips," he said.
"We are noticing a lot of causeways which were once safe are not safe at the moment, the roads are very slippery and there's still a bit of wind around as well."
Twenty-two schools across NSW were forced to close on Friday.
Communities risk isolation
The rising river levels pose a risk to some low-lying communities and could cut off road access.
Of particular concern is the rapidly rising Orara River on the Mid North Coast.
"Overnight we saw the Orara River at some points rise by approximately 70cm in an hour," Mr McLennan said.
He said the SES was concerned it could impact on the community of Coutts Crossing, as two of its main bridges on Armidale Road were being repaired.
"They have a diversion in place that takes it down onto the riverbank," Mr McLennan said.
"But if [the Orara River] does reach the predicted level of nine metres tonight, Coutts Crossing, McPhersons Crossing and potentially Nymboida will be isolated for a period of time."
The significant rainfall also prompted groundwater pumping in Stuarts Point near Kempsey on Thursday night due to concerns about some of the Kempsey Shire Council's septic tanks.
Rescue efforts commended
In the state's Hunter region, a local police officer could be recommended for a bravery award after rescuing three people including a child from floodwater.
The trio were stuck in their car on a flooded causeway at Dungog yesterday.
The senior constable from the Hunter-Port Stephens command used a rope as a safety line to reach the car and rescue the four-year-old boy and two women aged 51 and 44.
The local command said it would consider recommending the officer involved be recognised for his efforts and bravery.
