NSW - BECOMING UNSETTLED FRIDAY WITH A STORMY CHANGE SATURDAY BEFORE DRIER SUNDAY.

The weather is certainly remaining more on the active side than not over the course of the next 36hrs with some locally heavy rainfall and severe storms possible with the next change which is currently working through the Bight. The weather is expected to be unreliable in terms of broadscale rainfall totals of even distribution so be aware of that.


Following the change, a fresh and cooler southwest to westerly change will sweep the moisture further north and northeast through Sunday with the bulk of the wet weather forecast to remain over the QLD border with the tail of a trough hanging up and combining with onshore southeast to easterly winds.


High pressure ridging through the Bight will pass through to Victoria on Monday into Tuesday and this could lead to colder nights with light frost in the southeast but glorious days for much of the state away from the northeast.


The next change looks to approach the state from the south and southwest during next Wednesday which could produce a reasonable follow up rainfall event. It is too early to call the specific impacts for one location at this time, but for those looking at the working calendar and tryin to figure out when to get the outdoor work done for Winter and Spring, the weather turns for Wednesday through the end of next week.


Into the medium term, also looking at the weather impacting the tropics as moisture from the north and northeast could be drawn into the northern and northeast inland, especially as the SAM tends back more positive.

FORECAST

Rainfall Next 10 Days

Rainfall is forecast to be rather widespread over the course of the Friday night through Saturday with a robust band of rain and thunderstorms passing through the state. Some areas about the Southern and Central Tablelands and adjacent Plains could see in excess of 25mm from the event with a few falls getting close to 50mm. The rainfall lighter on the leeward side of the Great Dividing Range and over the far west. Rainfall will contract to the east and north overnight Saturday into Sunday. As we move into next week, showers will continue to impact the northeast of the state near a weak trough and onshore winds. The remainder of the state dry through to about next Wednesday. Now as we move through mid next week, we could see a widespread rain event develop once again with a sharp northward moving front coming into the state and interacting with modest moisture being absorbed in the northeast to northerly flow ahead of the system. Scattered showers and thunderstorms are possible from Wednesday and continuing through next week over much of the state but determining who gets what remains low confidence but that will be the next weather maker over the state. Some models have it one run, and then drop it the next, more clarity comes from the weekend onwards.

Thunderstorm Forecast Friday

Thunderstorms are forecast to develop along a prefrontal trough and approaching front during the afternoon and evening, with two bands likely to form in response. The prefrontal trough over Central NSW will kick off storms from about Bourke southwards to the Central and Southern Tablelands and possibly the Riverina. The second band will move through the Lower Western areas later tomorrow and likely to move into the Western Riverina tomorrow night and through Saturday. Damaging winds and heavy rainfall leading to flash flooding the main concern at the moment.

Damaging Winds Risk Friday

Damaging winds are possible with thunderstorms during Friday afternoon and evening, overnight into Saturday. A strong upper level wind profile could be drawn to the surface with the stronger storms during the afternoon and evening, resulting in wind gusts of over 100kmh possible.

Flash Flood Risk Friday

Flash Flooding is forecast to feature with strong thunderstorms and training bands of thunderstorms during the late afternoon and overnight period along the prefrontal trough. The higher risk of flash flooding along the frontal boundary will be in Victoria but a low risk looks to run along the Murray River.

MEDIUM TERM - May 6th- 13th 2022

Rainfall Anomalies

The rainfall bias has shifted to the east in recent broader guidance, given that we are seeing more drier and cooler air sweep the country. I am suggesting rainfall will be more aggressive over northern and eastern areas of the nation with the SAM tending back positive and with the lingering moisture courtesy of the lingering La Nina, the potential for a rainband to form in the north and east is quite likely. The west and remainder of the south seeing seasonal rainfall expectations. But the door is open for moisture to sweep south and southwest into these areas as well so watch closely.

Temperature Anomalies

A much colder signal has been triggered on the models with all in agreement we could see some quite fresh air being transported behind a strong cold front mid next week leading to the first chance of snowfalls on the mainland and the chance of frost for southern Ag areas of the nation so growers beware. The only thing offsetting the risk of severe frosts is that the SSTs around the nation are above normal and we do have a positive SAM phase unfolding in the east so while watching trends closely, there may be the chance some frost issues we could be talking about in around a week's time for the medium term.

DATA - Refer to video for more information and the model comparison and context about all the forecast products you see from me.


00Z GFS - Surface Pressure Pattern and Rainfall Distribution - Next 2 Weeks

A fast flow pattern unfolds this weekend with the strong cold front passing through. Then drier weather will resume for much of the nation. Next weather makers to watch are the southern system coming through over the course of mid next week. GFS dropped it tonight but the broader data sets have it. The other system to watch is the inland moisture building over northern parts of the country. Will that spread southwards into the medium term and provide the next inland rainfall event? Rainfall also picking up over WA in the medium term as well which could run across the country into the middle of the month so lots happening.

00Z GFS - Precipitable Water Values - Next 2 Weeks

Moisture is deepening over the east again ahead of a front passing through over the coming 36hrs but then it is out the door by Sunday and normal conditions resume for much of the country. As we track into the next week, we should start to see moisture building over northern areas of the nation and this could start to drift southwards and spread through the NT and QLD. Some of the medium term models want to spread that further south while other models spread through the moisture eastwards into QLD and NSW.

00Z GFS - Rainfall Accumulation - Next 10 Days

Refer to the video for more context and analysis

00Z CMC - Rainfall Accumulation - Next 10 Days

Refer to the video for more context and analysis

00Z Euro - Rainfall Accumulation - Next 10 Days

Refer to the video for more context and analysis

00Z GFS - Rainfall Accumulation - Next 2 Weeks

Refer to the video for more context and analysis

A closer look in - once we get the weekend system off the board I fully expect some pretty impressive rainfall events to appear on the charts, but being cautious and explaining those details is key to keeping expectations in check. So low confidence forecasting continues beyond the weekend system.

More coming up from 8am EST. Will be updating the climate picture from tomorrow too into mid June. Plus a review of the severe weather risks for this weekend as well over the east. A few days to take a breath next week which will be nice!


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