NSW - SHOWERS AND STORMS INCREASING TUESDAY AND POTENTIALLY HEAVY RAIN FOR ACT AND SOUTHEAST.

The complex nature of the weather pattern means that the forecast can change rapidly through this period meaning that some areas can have severe weather events evolving rapidly. There is evidence this may be the case for the southeast of NSW and the ACT and surrounding areas with a low pressure trough stalling out over the region and feeding off moist easterly winds to produce heavy rainfall leading to flooding.


For the remainder of central and eastern NSW may see showers and thunderstorms turning severe most afternoons and evenings but the most concentrated rainfall will be found over the southeast of the state and ACT. The latest modelling is divergent on where the heavy rainfall will appear but for consistency today the southeast is still the higher chance, but do not be surprised if the rainfall moves around in the coming days.


The west will remain dry and becoming hotter as we go along this week with a ridge close by.


Lets get straight into it.

FORECAST

Rainfall Next 10 Days

Rainfall is expected to be most widespread over the southeast and east of the state with heavy falls now looking to emerge near the ACT but a higher chance points east and towards the south coast with some chance of flooding in those southeast areas. The remainder of the state through central and eastern parts may see scattered showers and storms most days, that means uneven distribution of rainfall is likely to occur. The far west, fine and potentially dry for the coming 7-10 days at this stage. The main rainfall is expected for the southeast and east for the coming 4 days before it eases over the weekend, but the wet weather may remain in place over the northeast.

The heavy rainfall shield could move north or west through this region over the coming days so stay up to date.

Thunderstorm Forecast Tuesday

Thunderstorms are currently underway and will continue to develop overnight in isolated fashion but will likely tend more scattered and heavy by the afternoon and evening on and west of the divide through NSW and the ACT. Heavy rainfall and damaging winds the main risks, but if it does get hot enough, there may be some large hail concerns, for central and northern NSW. The storms will persist tomorrow evening into Wednesday.

Flash Flood Risk Tuesday

Flash flooding is a moderate to high risk as the airmass aloft becomes more humid and unstable, with high precipitation rates expected under thunderstorms. Some areas could see 30-50mm over the inland areas from the VIC border up to southern QLD with the main risk along the western slopes.

Damaging Winds Risk Tuesday

Damaging winds will continue to be a moderate to high risk over inland areas with the high precipitation thunderstorm activity. The main risks during the afternoon and evening and in areas that graduate above 30C. The main area of concern for central and northern parts of the GDR.

Large Hail Risk Tuesday

Large hail is a low risk for the central and northern parts of NSW with again, the main concern in areas that rise above 30C during the afternoon.

Riverine Flood Risk Tuesday

Additional flooding risks are possible for southeast NSW and the ACT plus surrounds with a large mass of slow moving thundery rain possible from Wednesday night through Friday. Some areas may accumulate between 100-200mm.

A closer look at who is in and who is out. This will refine.

DATA


00Z GFS - Surface Pressure Pattern and Rainfall Distribution - Next 16 Days

The GFS is spreading the rainfall over the nation in line with the CMC where the latest Euro has got a different idea in the short term for the east, more on that in the rainfall and model wrap after 9pm EDT. For now the most active weather rainfall wise will be found over the east and southeast this week, the west stays hot and SA, in the goldilocks zone, with seasonal weather for most of this week, hotter inland. No rainfall of note for most of western VIC, SA and southern WA. The tropics remain unstable and hot with storms, locally severe most days. The weather over the interior will be humid to start with but a drier airmass may begin to move in and this could see the heat engine over WA move southeast into SA, VIC, NSW, ACT and QLD from next week with drier weather potential which would be welcome.

00Z GFS - Precipitable Water Values - Next 16 Days

You can see the PW values are below average over the southwest and south of the nation nearer to the high pressure zone. For the north and the east, the moisture remains elevated with a deep supply thanks to onshore winds, the tropical northeasterly winds spreading moisture south through the nation, this pattern allowed to persist for most of this week, leading to the moisture building up to excessive levels. But in the areas closer to high pressure, dry and very hot weather is building and as the pattern flips, that heat will be projected across the south and east, so a break from the humidity over the south and east is quite likely, but replaced with high heat. Then as that heat develops, watch the tropical weather respond, with the humid air returning into the week leading into Christmas.

00Z GFS - Rainfall Accumulation - Next 10 Days

More on this coming up from 9pm EDT.

A closer look in - this will continue to change, the heavier rainfall will move around and with the divergence in modelling, it is low confidence forecasting as mentioned for the past week.

More on the rainfall and modelling after 9pm EDT and it will be very important information for those in the southeast of the state.



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