A band of intense rainfall and thunderstorms is about to drench many already overflowing rivers and flooded communities in New South Wales and Victoria, forecasters warn.
Stretching from southern Queensland to Tasmania, many areas will see up to 50mm of rainfall between Sunday and Monday morning, with 100mm or more expected in south-eastern parts of New South Wales and north-east Victoria.
The intense rainfall could bring large hail, damaging winds and intense bursts of rain to communities already suffering flooding after many months of drenching rain.
Much of Victoria was also under a warning that thunderstorms could trigger asthma, with the north of the state at highest risk.
Storms threaten to disrupt play at the T20 men’s cricket World Cup final in Melbourne between Pakistan and England scheduled to start at 7pm on Sunday evening.
The NSW emergency services minister, Steph Cook, told reporters on Sunday: “Once again it is the communities in inland New South Wales that will be in the firing line for these thunderstorms and heavy rain.
“Any additional rainfall that falls on our soils has nowhere to go, and therefore it increases the risk of life-threatening flash flooding and riverine flooding in the days ahead as our river systems try to absorb even more of the rain that continues to fall.”
Dean Narramore, a senior meteorologist at the Bureau of Meteorology, said a low pressure system had developed over the Great Australian Bight and combined with a cold front and moist tropical air to deliver a first hit of storms on Saturday to the Northern territory and South Australia.
Another band of rain and storms was moving across inland parts on Sunday. Heaviest falls were expected in the central west and Riverina areas of New South Wales and north-east Victoria.
Narramore said: “That’s going to lead to renewed river rises which isn’t good news at all. The atmosphere is pretty volatile and unstable and a number of the storms could have damaging winds, heavy rainfall and some of the stronger ones could have large hail.”
He said while thunderstorms were always “hit and miss” it was likely there would be storm activity around the Melbourne Cricket Ground for the T20 cricket final.
Rain was expected to ease on Monday and have cleared by Tuesday, but rivers would continue to peak throughout the week as the rain moved down already soaked rivers. There was a possibility of more weather systems bringing rain next weekend.
The NSW SES commissioner, Carlene York, said some communities could remain isolated for “weeks if not months” and there were 23 helicopters resupplying areas with food, medicines and animal fodder.
Communities could be affected well after the rain had stopped as rives kept rising and she pleaded for residents to heed warnings and to evacuate if asked.
She said: “The reason we are telling you is, your house or yourselves will be placed at extreme risk, and if the flooding does get to those major levels and you don’t evacuate, it is highly likely that we may not be able to get to you.”
The Bureau’s Steve Bernasconi said most inland rivers in NSW were on flood watch and asked residents to keep track of warnings in their areas.
The Edward, Darling, Lachlan, Murrumbidgee, Murray and Macquarie rivers were being watched closely.
The town of Warren had been subject to major flooding since the middle of September, and there was renewed risk of flooding for many towns including Bathurst, Molong, Dubbo, Wellington, Narromine, Condobolin and Forbes.