Issued Wednesday, November 29th 2017. New South Wales and Victoria are forecast to experience some of their most widespread significant rainfall for a long time, with some areas likely to experience more than a month’s worth of rain in less than a day! Above image via WindyTV (6 day rainfall forecast).
A low pressure trough is expected to enter Western NSW and VIC during Thursday afternoon brining showers, rain areas and thunderstorms to these regions. There is a chance of some severe thunderstorms due to heavy rain, but regardless of that scattered falls of 25-50mm and isolated higher totals are expected over Western VIC and SW NSW.
Conditions are then forecast to rapidly deteriorate over Friday and Saturday. During Friday, the trough moves slowly towards the East and becomes established over Central VIC and Inland NSW, generating widespread instability to its East which will lead to widespread thunderstorms (many of these severe for heavy rain / damaging winds) along with heavy rain areas. A low pressure region is expected to then become established on Saturday across Inland NSW producing further instability to its South and East leading to further scattered thunderstorms (again many becoming severe for heavy rain / damaging winds) and increased rain areas (especially to its South).
Low pressure region and rainfall areas during Saturday afternoon via GFS / WindyTV
Across the 3 days, widespread falls of 50-100mm+ are expected across Victoria (purple circle on cover image) and over large parts of Inland NSW (especially Southern / Central Inland regions) including Melbourne & Canberra. Scattered falls of 100-200mm are likely over Southern Inland NSW and North-East VIC (blue circle on cover image). These kinds of falls are not only double to triple the monthly average for these areas, but they have the ability to cause flash flooding across many areas (especially under thunderstorms) along with river and creek flooding which may reach minor to moderate levels for many areas. Conditions are expected to ease during Sunday.