Much of western, central and southern New South Wales and the ACT has just copped its heaviest rain in years, and with plenty more to come, is in for its biggest drenching in decades, according to weatherzone.com.au.

“Some centres have already had significant flooding this week with well over 100mm and are on target to pick up another 100mm in the next few days. This will tip some areas over the edge, in terms of record rain and biggest flooding in living memory,” Weatherzone meteorologist Brett Dutschke said.

Already this week places such as Broken Hill, Finley, Corowa, Albury, Coolamon and Grong Grong and Canberra have had over 100mm. Mt Ginini, near the ACT has had more than 200mm.

For the Riverina towns of Coolamon and Grong Grong, more than 100mm fell in one day, their highest daily total in more than 100 years of records. Albury also had more than 100mm in a day, its highest 24-hour total in at least 18 years.

Cooma on the Snowy Mountains is nearing 100mm for the week, not very unusual, but with about 400mm of rain so far this year the ground is water-logged and the Cooma Creek is lapping the town.

“With more than 100mm likely in the next few days, Cooma may exceed its annual average of 534mm, only 65 days into the year. The low pressure trough causing this rain will remain slow-moving until it finally moves to northern NSW on Monday,” Dutschke said.

In the past two days there has been a brief shift of the heaviest rain to central NSW, where Cowra and Oberon have had more than 80mm. This led to evacuations in Cowra.

“The trough has since moved back to southern NSW, taking the heaviest rain with it on Wednesday and Thursday. From Friday to Sunday it will return to central NSW then back to the south and back to central parts, giving the same places at least two-or-three days of drenching rain upon drenching rain.”

Canberra is on target for its biggest rain in 23 years and potentially its biggest in 62 years.

The nation’s capital has had 16mm since 9am today, giving it more than 100mm in under three days. If it gains 31mm in the 24 hours to 9am Friday it will have accumulated 130mm, which would be its highest three-day total since 1989. In that year, 159mm fell in three days, which is a three-day record. If by Sunday morning it gains another 100mm, which is possible, this would break its five-day record of 205mm, set in 1950.

“This sort of rain will lead to significant flooding and may cause water to overflow the new Cotter Dam.”

“Sydney is also in for some flooding, starting as early as Thursday night, when rain redevelops and becomes heavy. Rain should become lighter during Friday and switch off-and-on. Over the weekend, when the trough is making a few more passes over Sydney, there will be more heavy bursts, which will lead to further flooding. Thankfully for those planning outdoor activities it won’t rain all weekend but it will spoil some events. All up, between Thursday night and Monday morning more than 100mm is possible, most likely in southern and western suburbs. It may be the city’s wettest four days since last winter when 261mm fell.”

This will go down as another rain-ruined weekend, something which Sydney had many of during summer.

The forecast for next week is for cool southerly winds and showers being restricted to the NSW coast and ranges. Central and southern inland NSW and the ACT will stay generally dry.

– Weatherzone