Update, 4.13pm: AN extreme weather warning has been issued by the Tweed SES with 100mm of rainfall expected tomorrow and more than 200mm on Sunday.
All SES units are on full-alert from 7am tomorrow.
Initial report, 2.27pm: The Bureau of Meteorology has issued a flood watch from the Queensland border to Port Macquarie from Sunday onwards forecasting a greater than 75% chance of major flooding as well as local flash flooding, along the coastal river valleys.
Ex-tropical cyclone Oswald is expected to move south over the weekend into NSW and bring widespread heavy rain to the NSW north and mid north coasts and parts of the northern tablelands.
Major flooding is expected in the Tweed Valley, including Chillingham. The flooding is expected to develop from late Saturday into Sunday and Monday.
Major flooding is also expected for the Brunswick, Richmond, Wilsons and Clarence Valleys.
A flood watch means that people living or working along rivers and streams must monitor the latest weather forecasts and warnings and be ready to move to higher ground should flooding develop.