It is unsettled today through NSW and parts of eastern VIC and QLD. The weak trough that brought the relief in the form of southerly winds to the southeast is expected to remain slow moving and provide instability in conjunction with moisture to produce the widespread showers and thunderstorms from mid to late week.
The remains of TC Seth will be absorbed into a northeast flow and drawn into this trough with deeper moisture leading to thunderstorms producing moderate to heavy falls with a flash and riverine flood risk.
The trough and humid weather should lift out of VIC during Friday but remain in place over central and northern NSW during the weekend into next week so a long duration humid and storm event is a reasonable chance moving forward into mid January.
Many want to know the specific amounts of rainfall for their property, that forecast is not possible, so use the rainfall as a guide. Your number will vary.
Rainfall Next 10 Days
The rainfall looks most likely to be heaviest and more concentrated over the Riverina, Southwest Slopes, ACT and Southern/Central Tablelands at this time with the trough anchored through the region for a number of days. It is along and to the east of this trough is where you will find the heavier falls. The rainfall through VIC may be more patchy but isolated heavier falls are possible as the tail of the trough dips into Central VIC. For northern NSW and into southern QLD, the rainfall is expected to be scattered with some areas copping a soaking and others seeing very little. The storm activity will contract out of the southeast and become more widespread over northern NSW and southern QLD this weekend into next week. Overall, a humid and unsettled week expected.
DATA - Placement of the trough is everything and the below examples show that.
18Z GFS - Rainfall Next 10 Days
The very latest GFS places some very heavy rainfall over the ACT and points west back over the Riverina and Southwest Slopes suggesting the trough sets up camp and remains slow moving in this region with multiple rounds of rain and heavy thunderstorms in a humid airmass. The passage of the remains of Seth brings areas of heavy rainfall to the northeast NSW and southeast QLD coast. Further west through southern QLD, and northern NSW showers and thunderstorms delivers uneven distribution of rainfall and west of the trough, it is dry for the coming 10 days.
12Z CMC - Rainfall Next 10 Days
Heavy rainfall developing along and to the east of a trough is likely with severe thunderstorms delivering very high amounts of rainfall. Some areas would move into major flooding once again if this was to verify over the southeast of NSW and through northeast VIC. Rain along the east coast is with onshore winds and the passage of the remains of Seth. This may bring up to 100mm this week alone. Follow up rainfall is possible mid next week. Not much for western VIC and NSW and nothing for SA.
12Z Euro - Rainfall Next 10 Days
The Euro places the heavier rainfall over the southern inland of NSW extending over VIC with a multi day rain event. The showers and thunderstorms extend over the central and northern tablelands of NSW and with the passage of the remains of Seth, heavy rainfall may develop for the Northern Rivers and parts of Southeast QLD. This will need to be watched. The overall trend for inland QLD extending back to the tropics is uneven distribution of rainfall with showers and thunderstorms most days but west of the trough, you can see not much falls. So those looking for rain, on and east of the trough is where you need to be.
More specific details coming up tomorrow but understand, the trough may move further west and south which will mean your rainfall totals will change run to run. There is the risk of flooding redeveloping so be aware of this in the zones currently under flood warning. The highest risk is over southern and central NSW and the ACT.