Progs showing a substantial and long lived event. Showers, rain and storms every day from December 31 to about January 7. Best of it looks to occur from January 1-4.
A trough over eastern Victoria slowly edges west Wednesday and Thursday and is sat west of Melbourne by Friday. Areas on the eastern side of the trough sit in a warm muggy airmass with precipitable water values in the 30-40mm range with LI in the negatives. Progs vary in detail, but generally show 25-100mm. East central and the northeast currently tending to show the best of it atm. The trough slowly edges into the westerlies around Tuesday or Wednesday, but cold air aloft and return of a deep eastery flow suggest the pattern could repeat again in a week or so.
Tending to think 50-100mm in the Dandenongs at this point. Near the coast could also see sea fog. If you’ve got vulnerable plants might be the time to spray with sulphur or similar
Further north will be heavy falls making for a miserable week. Could be locally very heavy falls, particularly central Queensland coast and northeast NSW