More rain could hit the NSW coast as people living in already saturated catchment areas prepare for more water to flow to flood-stricken communities.

The Bureau of Meteorology said showers and storms could develop on the east coast on Sunday evening although inland areas that have received the bulk of recent rainfall were expected to be spared a further deluge.

But another storm system was forecast to develop over central Australia on Tuesday, bringing widespread rain and thunderstorms to eastern states by mid-next week.

On Saturday evening, the State Emergency Service told residents in parts of Narrandera, on the Murrumbidgee River in the Riverina region, to evacuate due to moderate flooding.

People in tourist and caravan parks at Moama were asked to prepare to leave, with an evacuation centre set up in the border town.

Heavy downpours in Victoria are expected to impact towns along the Murray River, including in Moama from mid-week.

On Sunday morning, major flood warnings were in place for 11 rivers in NSW with renewed flooding possible in some areas despite a temporary let-up in the rain.

Thousands of residents in Forbes, in the state’s central-west, have been affected by flooding after the Lachlan River peaked on Friday night.

NSW SES southern zone commander Benjamin Pickup on Saturday said it was possible rivers would rise rapidly even if the weather was fine due to the significant rainfall across western NSW over the past few weeks.

Major flooding from the Murrumbidgee River wasn’t expected to reach the town of Hay until late October, the BOM said.

October rainfall records have been set in parts of inland NSW, including at Broken Hill in the state’s far west.