A deep cold front associated with a low-pressure system in South Australia is moving across the state and causing severe storms.
The bureau said severe storms were detected at 3.15pm near Wisemans Ferry, Appin, Yengo National Park northwest of St Albans, St Albans and Badgerys Creek. The thunderstorms are moving towards the southeast and are expected to hit Wollongong, Richmond, Campbelltown and Penrith by 3.45pm and Parramatta, Gosford and Mona Vale by 4.15pm.
Bureau forecaster David Wilke said there would be a number of storm cells throughout the day with Thursday expected to be an “active storm day across NSW”.
A warning issued by the bureau about 1.30pm on Thursday afternoon said damaging winds and large hailstones were possible over the next several hours in locations including Sydney, Port Macquarie, Taree, Newcastle, Gosford, Wollongong, Nowra, Armidale, Orange, Goulburn and Tamworth.
“In the afternoon we could see another wave of storms,” Mr Wilke said. “Typically in Sydney we expect them in the late afternoon, that’s usually storm hour.
“But whether or not everywhere gets a storm is uncertain.”
The Bureau said at 2.15pm that severe thunderstorms were detected to the west of Picton, the Lithgow district and the southern areas of Lake Burragorang, in the Blue Mountains.
These thunderstorms were moving towards the south-east. They are forecast to hit Blackheath, Bargo and the Nattai Tablelands by 2.45pm and Wollongong, Katoomba and Penrith by 3.15pm.
On Thursday morning, the weather bureau issued a severe thunderstorm warning for Camden, Picton and Campbelltown with predictions of damaging winds and large hailstones.
The storms, which arrived over the Blue Mountains and moved in a south-easterly direction towards Wollongong, passed about midday and the warning was cancelled.
Damaging wind warnings mean gusts over 90km/h were expected. Large hailstones are defined as more than two centimetres in diameter, or the size of a cherry.
During storms the State Emergency Services advises people to secure loose items around the house and move any cars under cover or away from trees.
Weatherzone meteorologist Ben Domensino on Wednesday labelled the weather system the “beast from the south”, warning it would produce a dangerous mix of heavy rain, severe thunderstorms, damaging winds, hail and snow over parts of southern and eastern Australia over the coming days.
More storms are possible on Friday ahead of a fine and sunny weekend in Sydney, the first weekend in four months of eased restrictions when people can legally gather in large groups and visit homes.
Saturday and Sunday are both forecast to reach 23 degrees in Sydney.
The bureau on Wednesday issued a La Nina alert, meaning there is a 70 per cent chance of the weather event occurring in the coming months.
La Nina events increase the chances of above-average rainfall for northern and eastern Australia during spring and summer.
With Daniella White
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