Records are expected to be broken in the next two days with the Bureau of Meteorology expecting the Goulburn Valley to be hit hard by thunderstorms bringing from 100mm to 200mm of rainfall.
Senior forecaster Richard Carlyon said the bureau made the unprecedented move to issue severe weather and flood warnings on Wednesday to give people time to prepare for the band of heavy rain and thunderstorms slowly moving across southern Australia today and tomorrow.
‘‘We had a week of hot, humid weather and north-easterly winds have brought tropical air full of moisture that will combine with a strong low pressure system over the Mallee, where it will develop and then slowly move east,’’ Mr Carlyon said.
‘‘There will be substantial rainfall, the Goulburn Valley’s December rainfall average of 40mm will be reached and some locations across Victoria might end up with their summer average in the first two days of December.’’
The heavy rain is forecast to start falling at the end of this morning, with 50mm to 80mm predicted, while tomorrow is expected to bring a soaking of 50mm to 100mm.
There could be large hail and the possibility of damaging winds across both days.
Mr Carlyon said a few showers would be left on Sunday and there are also potential showers forecast on Monday and Tuesday that could have a significant impact on river levels.
‘‘I think there will be records broken, it’s difficult to compare to the 2010 weather event, but basic rainfall records for either one or two days are likely to be broken,’’ he said.
Widespread flooding is likely from today onwards in the catchments and people are asked to stay informed and monitor conditions.
The main rivers under flood watch are the Ovens, King, Broken and the Goulburn. The Seven and Castle creeks are also under flood watch and flooding may occur on the Campaspe River.
‘‘Plans are being cancelled or amended and I think if you can, it’s best to stay indoors,’’ Mr Carlyon said.
‘‘Local roads may be closed and low bridges may be underwater. Water crossings along streams and rivers will become dangerous as water levels rise.’’
The bureau has also released an advice warning for the potential of brown rot to form on stone fruit because of the high humidity levels the storms will bring.
Victorian Farmers Association president David Jochinke said the low-pressure system may dump more than 300mm of rain in Victoria’s north-east, which could spoil remaining crops.
Some farmers have worked during the night frantically harvesting their crops, in a race to beat the bumper rainfall.
Goulburn-Murray Water is urging its customers and northern Victorian communities to keep an eye on updates from the bureau ahead of significant rain expected.
G-MW’s managing director Pat Lennon said the customer operations team was monitoring the situation closely and working with storage staff, the bureau and State Emergency Services representatives.
‘‘Some of G-MW’s water storages are already near capacity and others may receive significant inflows. We are currently preparing for the forecast conditions in accordance with our operational arrangements,’’ Mr Lennon said.
‘‘Please keep an eye on BOM updates and heed any flood advice they may issue. Flood warnings will be issued by BOM.
‘‘People living near rivers, creeks, storages need to monitor the situation and prepare themselves and their properties, according to their flood plan.’’
G-MW customers are reminded that before pumping any excess flood water from their property into G-MW irrigation or drainage channels, they must first seek permission from a planner via WaterLINE on 1300469469.
Residents can monitor flood warnings on the Emergency Management website at www.emv.vic.gov.au and request emergency assistance by phoning the State Emergency Service on 132500.