The Bureau of Meteorology sounded the major flood alarm on Tuesday, signalling the most severe flooding of the Forbes town since 1952 was on the way.

Friday looms as D-Day for the town, with the Lachlan River at Forbes' Iron Bridge likely to exceed the major flood level of 10.55 metres on Thursday.

The river level may reach around 10.80m on Friday, which would trigger a major flooding event similar to the June, 1952 flood.

The flood event has been triggered by rainfall over several days and weeks which has caused renewed and prolonged flooding along the Lachlan River and its tributaries, the bureau says.

Spills from Wyangala Dam, combined with inflows from the Boorowa River have caused moderate flooding along the Lachlan River at Cowra, with river levels remaining steady since 12am on Wednesday, November 2 near 12.25m just below the major flood level of 13m in Cowra.

Many low-lying areas of Cowra were issued an evacuation notice on Tuesday as the river's levels rose.

Further down river, levels at Nanami exceeded the major flood level of 10.7m at around 4am on Wednesday, November 2, with the peak expected overnight Wednesday into Thursday.

As the peak moves downstream, that's when the major flood levels at Forbes will occur.

On Tuesday, Forbes Mayor Phyllis Miller was urging anyone whose property becomes isolated to stock up on essentials.

"Please go and fill up on your groceries and all of your medical needs that you require," she urged in a Forbes Shire Council Facebook post.

"We will be having an emergency management committee meeting at lunchtime today and I'll know a bit more, but at this point in time please be prepared.

"Make sure you know the capability of your property.

"I believe we're going to have a major flood, so we all need to work together to stay safe."

Storms lashed Forbes, particularly hitting North Forbes hard, on Monday night, but there were heavy falls across the region.

It comes on top of a relentlessly wet three years for our region, with Wyangala Dam filling repeatedly and our catchment saturated.

Meanwhile at Young, the SES has rescued two people swept off a causeway near Bribbaree.

At 9.30am on Wednesday, November 2, the SES responded to a call for help near Bribbaree, where two men were reportedly clinging to the side of their car.

A SES Flood Rescue team from Wollongong responded to the incident.

The current incident is the fourth flood rescue that SES have responded to locally with the two men near Boorowa still missing.

"Boorowa police and SES resumed searching again today," the spokesperson said.

The SES along with Hilltops Council and local police are pleading with motorists to not take any risks and not attempt to drive through floodwater.

Forbes though remains the main concern for the Central West, with NSW SES revealing that community, along with those along the river systems of Kingdon Ponds (Scone), Barwon (Walgett), Darling (Bourke and d/s), Lachlan (Forbes and Condobolin), Murrumbidgee (Gundagai, Hay) and Murray (Moama/ Echuca and downstream) are being carefully monitored.

The NSW SES says, in the last 24 hours, there have been 664 requests for assistance and 29 flood rescues. Much of NSW SES' efforts are focused on sandbagging, flood rescues, resupply and fodder drops.

Floodwaters continue to rise and cut roads across the region, with the Newell Highway south of Forbes closed to all vehicles on Monday after several days of access to 4WD and all-wheel drives, then heavy vehicles only.

Minister for Regional Transport and Roads Sam Farraway is urging motorists to be aware of the difficult conditions and to delay any non-essential travel.

"Safety is our number one priority for all road users and we can't stress enough how important it is for everyone to take extra care over the next few days," Mr Farraway said.

"The recent extreme weather has badly damaged roads right across the state's network and the forecast of more rain and possible snow only adds to our concerns.

"We remind all motorists to never drive through floodwater and to never drive around road closed signs. These signs are there for your safety.

"If you do need to travel, please drive to conditions, allow extra travel time and follow the directions of signs and traffic control."

As of Wednesday, road closures around Forbes included:

There was some water over the Newell Highway to Parkes; and water over the Bogan Way between Forbes and Bogan Gate.

For the latest traffic updates on state-controlled roads and highways, call 132 701, visit livetraffic.com

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