Once again staring down some interesting signals for widespread rainfall building from later Sunday into Monday with a persistent upper low forecast to remain in place over QLD until the end of next week.

The placement and position of the upper low is paramount to where the heaviest of the rainfall will be occurring under this current situation.


Rainfall Next 10 Days - QLD

Widespread rain is forecast to emerge from Monday throughout much of inland QLD and this rain is forecast to increase in coverage and intensity as we move through next week. A surface trough along the coast could also enhance rainfall in advance of an upper low moving east from the NT. The deep moisture being lifted to full potential with widespread heavy rainfall possible leading to areas of flooding. The heaviest of the rainfall is forecast over the eastern coast and adjacent inland with some spots possibly clearing 200-300mm of rainfall for the event but with elevated SSTs through the region and the northeast to easterly flow, some areas could see 500mm for the event. The inland also seeing above average rainfall and the risk of severe thunderstorms is relatively a high risk. These will produce heavy rainfall that too will lead to flash flooding. The rain begins to clear east at this stage from later next week. Forecast confidence is MODERATE.

Rainfall Next 10 Days - NSW

Rainfall is forecast to emerge through the eastern inland of QLD from Monday and begin to shift south from Tuesday next week with some locations over northern and northeast NSW forecast to see heavy rainfall that may lead to flooding once again. The rainfall shield will drift further south through this time next week and it is unclear how far south that rainfall will come but confidence is increasing that the higher risk area for above average rainfall will be in the cental and northern districts as well as along the coast north of Gosford for now. The rainfall could lead to moderate flooding developing over northeast NSW during the latter part of next week as the upper low moves towards the coast. The position and depth of a surface trough along the coast is also critical for the heavy rainfall smear across the state. Forecast confidence - MODERATE.

Riverine Flood Risk - Wednesday-Friday

The heavy rainfall potential next week may lead to riverine flooding redeveloping over a large area once again, but it is more likely about the east coast between Cardwell and Coolangatta at this time. Flash flooding via thunderstorms also quite likely for inland areas.

Severe Weather Watch - Monday to Friday

The watch area has been extended southwards over the southern border and further west, but this risk will continue to chop and change, be weather aware and pay attention to forecasts.

GFS - Upper Air Pattern - Next Week.

How the trough evolves into a low-pressure system, how fast the system moves into the east and how much moisture it picks up on all remains up in the air. There is some case for widespread rainfall and flood potential once again through the east but narrowing down the low to high-risk zones will remain tricky for the next few days. Once the system is being tracked in real time (from the weekend) that is when confidence begins to improve.

GFS - Rainfall Spread - Sunday through Friday

Can certainly see the impact of the upper-level low moving into that moisture via the easterly winds and positive SAM phase. This has the hallmarks of another severe weather event for QLD and parts of NSW with flooding the main concern and severe thunderstorms with a flash flood risk also a high concern on current guidance. But once again, we are a few days out from having the confidence in the forecast improve.

GFS - Rainfall Accumulation - Next 10 Days

This takes in the event from next week, not much rainfall is forecast ahead of the feature, but you can clearly see how far west the moisture arrives before it is lifted and taken back as a large rainfall event. There is some chance the rainfall could extend over the borders into SA and the NT in a more widespread fashion so areas along the border need to watch the trends carefully. Certainly, a growing flood event is appearing along the Central, Wide Bay and SE Coasts and adjacent inland.

GFS - Rainfall Accumulation - Next 10 Days

The rainfall does look to drift into NE NSW where there have already been significant flood issues over the course of this year and this event, while not as amplified as previous events, would renew some flooding for parts of the disaster zones. Inland rainfall determined by the position of the upper low and whether it moves into QLD or runs along the northern border next week. Overall, a very wet look for much of NSW. There is some chance that the rainfall could indeed clip the east of SA and possibly come as far south as the northern parts of VIC as well.

More coming up in the state-based forecasts tonight! But this is looking more likely to be a severe weather event and preparation needs to be now if you are in a region vulnerable to flooding.