In a surprisingly wet month, eastern New South Wales is set for another drenching, this time focussed on the northeast.
Yamba has already led the charge for the next major wet spell, picking up its heaviest August day of rain since 2011 with 39mm. But even Yamba is set for greater achievements.
A low pressure trough has developed off the southeast Queensland and NSW coast. The trough is providing enough instability for moist onshore winds to produce showers along the NSW coast and areas of rain over southeast Queensland.
Tonight the areas of rain will start to include the Northern Rivers and then the Mid North Coast during Saturday. On Sunday the trough will shift further offshore, allowing rain to tend to isolated showers. This will bring a brief reprieve before things get serious next week.
On Monday, an east coast low is likely to start developing within the trough, deepening markedly on Tuesday. This will then produce areas of heavy rain, most likely focussing on the Mid North Coast, but could also hit as far south as Sydney or as far north as the Northern Rivers. Regardless of the position of the low, plenty of showers will spread all the way to the South Coast on Tuesday in unstable onshore winds.
The greatest danger from this system is for flooding. In the next seven days, the Mid North Coast and Hunter are likely to see widespread totals in excess of 150mm, with isolated falls above 300mm producing significant flooding.
Farmers over the Northern Tablelands and the Northwest Slopes and Plains should be paying close attention to the forecast in the next few days, as there is likely to be some follow-up rain to last week's good winter dose. August is one of the driest months of the year for eastern Australia, so this wet spell is seen as a bonus by many farmers. On Tuesday and Wednesday, an upper cold pool is likely to move across the region. At this stage there is some doubt about how much will fall, but indications are in the order of 5-15mm widespread across the region.
On Thursday rain will start to ease up along the NSW coast as the main low pressure system starts to move away. By the weekend it should finally be mostly dry, with just a few coastal showers left over.
© Weatherzone 2014
11:37 EST Tens of thousands of people are without power and SES crews have answered more than 3,000 emergency calls as heavy rain and "cyclonic" winds topping 130kph continue to lash Sydney, the Hunter and the NSW Central Coast.