BoM senior meteorologist Scott Williams said some parts of the state may receive up to 100 millimetres of rain in that time.
“We’ve already seen about 11mm of rain fall down over Casterton since 2pm this afternoon, and there’s a fair bit of rain coming from the South Australian border now, with the heavier falls to come,” Mr Williams said.
“What we’re expecting is thunderstorms, which have been seen out to the north-west of Mildura, coming down into north-west Victoria late this afternoon and into the evening.”
He said these storms could be potentially severe.
“The storms could dump up to 50mm of rain in just one hour, and there’s a chance we could see some hail as well,” he said.
“The Grampians and Wimmera will see heavy rain develop later in the evening, from about 9pm, which will then last through the night, and continue into Thursday.”
He said the east of the state will also see its share of showers.
“But the heaviest rain looks like being in a band from Swan Hill, southwards towards Ararat and then down towards Mortlake and Warrnambool,” he said.
“There’s a narrow corridor which suggests 100mm is quite likely, but on either side of that we’re still looking at 30-50mm fairly widespread back towards the South Australian border, and also across to Bendigo and Ballarat, and even the western side of Melbourne and Geelong.”
He said following a few days of warm weather, temperatures should drop quite dramatically.
“As that low forms, we’ll see colder southerly winds develop in the south-west district, so that poses a major risk to sheep, and lambs in particular,” he said.
He said at this stage, there are also chances of flooding.
“Even though we’re almost in summer, be aware that there could be some flood warnings,” he said.