NCSC: "Second image is ACCESSG, showing us there are falls up to 300mm possible along the coast with 80 - 150mm inland."

300mm of rain set to drench the Northern Rivers

NORTHERN Rivers is set to get a drenching this week, with up to 300 millimetres of rain falling by this weekend a forecaster has predicted.

North Coast Storm Chasers forecaster Antonio Parancin said on Thursday widespread heavy rainfall and a possible low could form from mid this week.

"Onshore winds interacting with a deepening trough will develop offshore then move onshore south-east Queensland and north-east NSW, delivering 100 to up to 300mm in some locations," Mr Parancin said.

"NE NSW will see heavy falls and totals possibly penetrating further inland all the way to the Tablelands."

He said there were three major weather model predictions for rainfall amounts and locations, all roughly showing 150mm-300mm of rain on the coast and a possible 60-150mm inland.

The Bureau of Meteorology said later on Tuesday or Wednesday a trough is forecast to bring a fresh southerly change to southern parts of the coast.

BoM predicts heavy showers from Tuesday onwards.

There is a high chance (90 per cent) of 15-35mm of rain in Byron Bay on Tuesday and up to another 20mm forecast for Wednesday, with a possible late storm on Thursday.

Similarly, in Ballina 15mm to 30mm is predicted for Tuesday, and another 15mm on Wednesday.

Lismore could receive up to 25mm on Tuesday.