Parts of Sydney have been battered by heavy rain and hail, as severe thunderstorms continued to sweep across the city late into the night.
The Bureau of Meteorology (BOM) said the rapidly evolving weather could cause flash flooding, earlier issuing a warning that “very dangerous thunderstorms” were detected on the weather radar near Hornsby, Parramatta and Warragamba.
The east-moving storms were forecast to affect the Sydney metropolitan area, Liverpool and Penrith, along with and Bankstown, Fairfield, waters off Bondi Beach and parts of the Central Coast later on.
As the storms moved through, warnings for severe thunderstorms in the Northern Rivers, Mid North Coast, South Coast, Southern Tablelands and Northern Tablelands districts were cancelled.
Harrington Park in Sydney’s south-west was pelted by hail, while in Bankstown, cars were seen entering floodwaters.
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Hail measuring up to 6 centimetres was recorded in Glenbrook in the Blue Mountains, and BOM said golf ball-sized hail measuring more than 4 centimetres was also recorded at Stanhope Gardens and Kellyville in Sydney’s north-west.
Images posted on social media showed backyards blanketed in a sea of white.
At Mona Vale on Sydney’s northern beaches, 90 millimetres of rain fell between 8:45pm and 9:45pm.
Murray’s Flat near Goulburn and the Goulburn Water Treatment Works received 82 millimetres and 43mm in two hours respectively.
Doughboy Hill recorded 45mm in two hours, while 41mm fell at Big Hill (Glen Dusk near Goulburn) in one hour.
Bankstown in Sydney’s south-west recorded 17mm falling between 9:00am and 3:00pm.
Endeavour Energy said about 8,500 homes were without power in the Illawarra and Macarthur region, while Ausgrid said 11,000 homes were without power, particularly in Sydney’s northern suburbs and northern beaches around Manly and Fairlight.
The NSW State Emergency Service said it had received 630 calls to its operations centre, with 350 of those being attended to by SES volunteers.
The worst-affected affected areas were Blacktown and Goulburn, where there were 100 and 33 calls-outs respectively.
There were 37 calls from the Hills District and 25 from Liverpool.
Media officer Phil Schafer said most of the jobs were for fallen trees and leaky roofs, while one flood rescue was carried out for a person trapped in a vehicle at Wollongong.
Mr Schafer warned drivers to stay out of floodwaters.
Domestic flights at Sydney Airport experienced delays of up to 90 minutes, but there were no delays to international flights.
At one point, passengers flying with Virgin Airlines were told that planes were not taking off due to lightning around the airport.
The airport advised passengers to check with individual airlines on the status of their flights.
Up to 60mm — almost half the city’s average rainfall for the month of March — was expected throughout the eastern Sydney basin on Thursday.
BOM’s Rosemary Barr said it was a rapidly evolving system with the potential for flash flooding.
“We could definitely see for isolated regions … flash flooding, and that’s something we’re concerned about, particularly with heavier thunderstorms coming across,” she said.
“These showers will deliver varying amounts [of rainfall] but we could see pretty heavy falls and particularly at isolated locations.”
Ms Barr said the series of individual storm cells were part of a larger system stretching from Goulburn through the Sydney basin and the Blue Mountains to the Northern Tablelands.
“So you can think of [the storms] as a pot boiling — you have got individual bubbles, they are our thunderstorms, but the pot itself is out weather system.”
She said isolated rainfall was expected for the next few days, particularly along the state’s coastal fringe.
Sydney is forecast to receive between 15mm and 45mm on Friday, with a chance of a thunderstorm in the morning and afternoon.
On Saturday and Sunday there is a chance of showers, with up to 6mm of rain.
Although Sydney city only received 8mm yesterday, outer parts of the city — particularly the northern beaches region — received up to 50mm.
Observatory Hill, near The Rocks, recorded 111mm over the whole day, while Chatswood followed with 107mm.
The March average rainfall at Observatory Hill is 130.8mm, while the highest-ever total rainfall recorded was 521.4mm in 1942. The lowest was 8.4mm in 1964.