New South Wales is expected to be inundated by sustained rain, with flooding possible and a 14-day spell of rain on the horizon

Sustained rain is intensifying across New South Wales, increasing the risk of flooding around Sydney and the Illawarra this weekend.

Interior parts of the state can also expect widespread rain over the next 48 hours, starting in the west on Friday and then moving to the foothills and mountain ranges on Saturday.

Following the weekend’s rain, the seemingly endless wave of coastal rain is likely to persist into next week and is likely to push Sydney’s May rainfall total to more than 200 millimeters for the second month in a row.

The rains will intensify this weekend

We are now on the fourth day of a blocking pattern in which a stalled high pressure system west of Tasmania has brought a prolonged period of southerly winds and rain to the New South Wales coast.

More than 100mm has already fallen around Sydney’s northern beaches and the central coast this week, almost eclipsing the average for all of May, although the minimal extent and short duration of each downpour has prevented major flooding.

While the surface weather map will remain identical this weekend, what will change and increase precipitation is what is happening a few kilometers above the ground: an upper trough (a low pressure system overhead) is moving in. will move east across the state.

The heaviest falls on Friday will fall over the west of the state (below the low), with a wide swath from around Cunnamulla to Pooncarie, including Cobar, Ivanhoe, Wilcannia, Bourke and Brewarrina, likely to see 15 to 50mm.

Charging…

Meanwhile, rain will also continue in the east until Friday, with the central stretch of coast from the Illawarra through Sydney to the Central Coast again likely to experience the heaviest falls.

The western rain band will extend eastwards on Saturday, enveloping most of the state, including widespread falls of more than 20mm over the inner north and around Sydney.

Rain should intensify further on Sunday along the coast as the eastward-moving upper trough interacts with moist onshore flow from the Tasman Sea.

Up to 100mm could be seen in 24 hours from the Illawarra to Sydney on Sunday, possibly enough to cause some pockets of flash flooding according to Angus Hines of the Bureau of Meteorology.

“If we see triple digits… 150mm is not out of the question… that is certainly enough to cause areas of flooding, we could well see some impacts on the ground,” he said.

Hines also warned that while it is too early to issue specific warnings, this could change this weekend.

Most of New South Wales can expect at least 20mm of rain over the next week, with more than 100mm should fall in eastern Sydney.

Continued rain this weekend will also cause river flooding and the possibility of minor flooding in some of the smaller coastal catchments, although rainfall totals and flooding should remain well below last month’s extreme levels.

Regardless of the reduced severity, NSW SES Acting Deputy Commissioner Allison Flaxman said volunteers and flood rescue operators were ready if needed.

“We are working closely with the Bureau of Meteorology and are monitoring conditions across the state,” he said.

“It cannot be ruled out that isolated rainfall exceeding 100 millimeters may occur in some coastal areas, but we are well positioned to respond to any request for help.”

When will the endless rain finally disappear?

The spell of wet days will continue along the New South Wales coast from Monday to Wednesday, before another area of ​​rain possibly arrives from the west around Thursday.

Some models are even hinting at another maximum lockdown near Tasmania during the second half of next week, a scenario that could extend the flow of onshore winds and rain into mid-May.

It’s not inconceivable that Sydney’s streak of rainy days could exceed 14, the longest rainy streak since early 2022, when 17 consecutive days had measurable rain, but still well below the longest rainy streak on record. of Sydney for 29 days in early 1891.

However, if we consider that a rainy day requires at least 1 mm of rain, the record of 16 days between 1943 and 2022 could be threatened.

So when can eastern New South Wales expect a full 24 hours of mostly clear skies? Models show that the blocking system should break by the third week of May, allowing our weather systems to become mobile again and wash rain off the coast.

Rain fills dams and eradicates drought

It was not until last spring that serious concerns about drought, wildfires and water shortages were raised by numerous agencies following an unprecedented dry August to October and the declaration of El Niño.

By November, 65 per cent of New South Wales had entered some level of drought and Sydney’s water supply had fallen to the lowest level in three years, although it was still close to 90 per cent.

After six wetter-than-average months, the drought is now limited to just 41 percent of the state, of which only 2 percent are not classified in the least severe drought category.

Above-average rainfall during the warmer months also moderated bushfire activity and increased Sydney Dam levels, which are now back to near capacity.

Additional rain in May will further reduce 12-month rainfall deficits and may lead to another minor spill at Warragamba Dam.