Areas worst affected will be the NSW mid-north coast, the Hunter, Sydney, as well as the Illawarra and south coast regions.

Alpine areas above 1200 metres in the southern tablelands, south-west slopes and the ACT will also be lashed by the storm.

Widespread damaging winds and locally destructive gusts of up to 125km/h in some coastal areas, as well as flash flooding, are expected later today.

The developing low pressure system off the NSW coast is expected to intensify and move closer to the coast later today.

Winds on the south coast, Illawarra, Sydney, Hunter, mid-north coast and alpine areas of the southern tablelands, south-west slopes and ACT are expected to average more than 65km/h.

Peak wind gusts are expected to exceed 90km/h.

Locally along the coastal fringe, winds could average in excess of 90km/hour, with gusts in excess of 125km/hr.

Blizzard conditions are expected to develop this afternoon or evening in Alpine areas of the southern tablelands, south west slopes and the ACT above 1200 metres.

Heavy rainfall leading to flash flooding is possible on the south coast, particularly in the far south.

Emergency services has advised people to keep clear of fallen power lines, stay indoors away from windows and keep children indoors.

Emergency services has advised the public not to walk, ride a bicycle or drive through flood water, and keep clear of creeks and storm drains.

The National Parks and Wildlife Service recommends that people consider postponing back-country travel until conditions improve.

For emergency help in floods and storms, ring the SES (NSW and ACT) on telephone number 132 500.

The next warning is due to be issued by 9.30am today.

A number of gale and wind warnings are also current for NSW coastal waters.

On the south coast, a gale warning is current from Gabo Island to Moruya, with seas rising up to five metres on a rising to three- to four-metre swell.

A gale warning is also current for the Sydney's closed waters, Pittwater, Port Jackson and Botany Bay, with waters becoming very rough.

Storm force winds are expected from the mid-north coast south along coasts in the Hunter, Sydney, Illawarra, to the south coast - from Seal Rocks to Moruya.

A strong wind warning is current for the far north coast, from Tweed Heads to Smoky Cape and from Smoky Cape to Seal Rocks.

Huge seas rising up to six metres on three to four metre swells will batters coasts tonight.

The third major storm of this month for NSW will rock the bulk carrier Pasha Bulker, which has remained stranded on a sandbar off Nobby's Beach in Newcastle since the first big storm hit on June 8.

The first round of fierce weather caused widespread flooding in the Hunter and Central Coast regions through last week, cutting power to 200,000 homes.

A second storm that followed at the weekend brought more damaging winds, while heavy rain took Sydney's rainfall for June to more than 350mm.

The State Emergency Service in Sydney and surrounding areas has received almost 18,000 calls for assistance so far this month.

The Bureau of Meteorology said while the rain was not expected to be as heavy over the next couple of days, wind speeds in some areas could approach 100km/h.

"There will be gale-force winds about coastal parts especially Tuesday night and Wednesday in the south and central coast of NSW," BoM spokeswoman Deryn Griffiths said.

"We're looking at not a large amount of rain compared to our last couple of events, but there will be rain along the coast and snow up on the ranges."

Bulk carriers weigh anchor off Newcastle, 19 June 2007

More than 50 bulk carriers off Newcastle are heading further out to sea ahead of forecast wild weather.

Newcastle Port Corporation spokesman Keith Powell said 52 vessels have weighed anchor and are heading away from the coast after being advised 50 knot winds and seven metre seas are expected to develop in the area tonight.

Up to 16 vessels remain at anchor off the coast, but they are also expected to follow the others to deeper water, Mr Powell said.

The flat-bottomed bulk carrier Pasha Bulker remains firmly grounded on sand 20m off Newcastle's Nobbys Beach after gale force winds and wild seas on June 8 drove it aground.

It will be pounded again by huge swells overnight, but Mr Powell said there was no current concern about the hull's integrity, or that it might tip over.

NSW Maritime is investigating whether some ships ignored the strong weather warnings for June 8, resulting in the Pasha Bulker's grounding and close calls for at least two other vessels.