"With all the rain over the weekend we are still seeing significant flooding for large parts of the country - particularly for Bathurst and Forbes," Bureau of Meteorology Senior Meteorologist Jonathan How said.
Severe flooding hit numerous regional towns across NSW on Monday, with 100 people rescued from roofs in the central west town of Eugowra and extensive flood damage seen in nearby Molong.
On Tuesday, emergency warnings stretch from the Queensland border through to Victoria, with major flooding expected at the regional centres of Forbes and Bathurst.
Renewed inundation is expected to begin in Forbes on Tuesday as the Lachlan River reaches major flood levels, peaking on Thursday.
The warning comes just over a week after Forbes experienced record flooding damaging local businesses and roads.
"For many of these rivers, once we see the peaks upstream we will have a better idea of what we can expect further downstream," Mr How said.
It comes after forecasters warned of significant flooding in Bathurst on Monday with fears record flood levels of more than seven metres would see flood levees overtop.
A cold front will move to the south on Tuesday, with some snow expected in southern parts of NSW, before a high pressure system from the south sees conditions clear on Wednesday.
"This is a very serious situation," Emergency Services Minister Steph Cooke said on Monday.
"The entire central west of NSW has been hit very hard in the last 24 hours.
"The ground is so saturated, that all it takes is one heavy downpour to cause the type of life-threatening flash flooding we have experienced overnight and into today."
"This (severe weather) event is now in its 62nd day, and every day it throws up new challenges."
Four people died in the last 62 days as a result of the severe weather, although no deaths were reported in the previous 24 hours, she said.
Twelve flood rescue operators were flying in from New Zealand to support exhausted State Emergency Service crews in Parkes, Ms Cooke said.
"The SES is now also working with authorities in Singapore and the United States of America to secure additional support."
It was the first time the SES had made a request for overseas assistance, SES Commissioner Carlene York said.
"Because of the length and the devastating effects of these floods."
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