A powerful low pressure system will cause damaging winds, heavy rain and large waves in Victoria and New South Wales this Friday, along with a burst of cold weather that will bring early-season snow to mountains in four states and territories.

A cold front crossing southeastern Australia on Thursday will cause a low pressure system to spin up over the western Tasman Sea on Friday. While the cold front will bring its own surge of cold, wet and windy weather, the low pressure system will be the most dangerous part of this weather event.

Rain and thunderstorms will spread across southeastern Australia on Thursday as a southwesterly wind change associated with the front causes temperatures to drop over Tasmania, Vic, NSW, South Australia and the ACT. Snow is expected to start falling in Tas and Vic on Thursday, possibly reaching around 1000 metres above sea level in Tas during the afternoon and night.

On Friday, southerly winds will strengthen considerably over eastern areas of NSW, Vic and Tas, and the ACT. These powerful winds will be caused by a low pressure system deepening rapidly over the western Tasman Sea, most likely centred off the south coast of NSW. Damaging winds are likely to affect parts of NSW and Vic on Friday and will probably extend to the ACT and eastern Tas as well.

In addition to the wind, heavy rain and highland snow will affect eastern Vic and southeast NSW on Friday. Some areas could see 50 to 100 mm of rain during Thursday and Friday combined, which may cause localised flash flooding.

The coasts in eastern Vic and NSW will also get hit by huge waves on Friday and Saturday, with wave heights expected to reach around 3 to 5 metres, possibly exceeding 5 metres along the NSW coast late Friday into Saturday morning. These waves will make coastal activities including swimming and fishing dangerous, and they will cause coastal erosion at south-facing beaches.

This week’s burst of wintry weather will be a noticeable change from the recent warm spell in southeastern Australia:

Melbourne’s maximum temperatures have reached 27 to 30°C during the last four days. The city’s maximums are forecast to drop to 18°C on Thursday and 16°C on Friday.

Hobart is forecast to reach tops of 16°C on Thursday and 15°C on Friday. This would make Friday the city’s coldest day so far this year.

Canberra’s temperature is forecast to only reach as high as 15°C on Friday. This follows a week-long run of temperatures above 26°C during the past seven days.

Sydney will see a temperature drop of about 10°C in 24 hours, with maximums forecast to reach 30°C on Thursday and 20°C on Friday.