A DRY WEEK - THEN RAINFALL FROM FRIDAY FOR INLAND NSW.

As mentioned yesterday, a settled and quiet week on the way under high pressure. Cold nights and sunny weather to follow from today through Thursday. Only high cloud the only complication for the region. Temperatures will slowly move above the average come later this week as a northwest flow returns.


That is ahead of a trough deepening and spreading rainfall throughout the eastern inland of NSW which may spill over into VIC and QLD as the trough moves through.


But each model has a different idea of where the system goes and this impacts rainfall - here is the track of both models with my rainfall forecast splitting the difference underneath.


Where does the low go? Which model would you trust? There are more questions than answers this morning hence why you are seeing rainfall changing on the modelling this morning, so expect that to continue for another day or so.

That system could be quite productive, with all models at one point or another showing heavy inland falls through most of NSW west of the divide, but models have not been in agreeance at the same time, so it makes it hard in terms of forecasting rainfall with great confidence. So a low confidence forecast tag applies to this system.


Rainfall for the next 10 days - Valid Monday 5th of July 2021.

Pinning down rainfall is quite tricky with broad areas expected to see something later this week, but where the trough lifts the moisture, how fast the system moves through from northwest to southeast and whether a low forms along the trough will determine who gets what and how heavy that rainfall could be. This system has a spring time look to it, in terms of it's evolution and track, so surprise heavy rainfall may continue to spread if the GFS solution wins out over the Euro.

Rainfall for the next 10 days - Northern and Central Inland NSW - Valid Monday 5th of July 2021.

A closer look at the spread through the northern inland of NSW shows where you stand rainfall wise, but I caution you, this will change, if GFS is right, then numbers will double through the region. I will draw a map for southern inland areas of NSW later today as we get better handle of the rainfall as the numbers have been bouncing around with the low being there and not being there run to run.

Lets have a look at the modelling relating to NSW.


GFS 12z run - Rainfall spread for the next 10 days - Valid Monday 5th of July 2021.

This run of GFS is much more aggressive with the rainfall that is in line with a trough deepening and a low forming on the trough later Friday or Saturday before moving southeast off the southeast coast of VIC/NSW. This run has a stronger front moving through the southeast early next week with a better push of rainfall.

GFS 12z run - Surface pressure pattern and rainfall distribution - Valid Monday 5th of July 2021.

Notice the low pressure system forms along the trough as it pushes through the eastern inland with rainfall increasing in line with this modelling. The low cuts off from the upper westerly flow which will be in place through the interior taking the system southeast rather than eastwards. So that will be key to rainfall distribution and something to watch during the coming few days.

Euro 12z run - Rainfall spread for the next 10 days - Valid Monday 5th of July 2021.

The Euro has reasonable rainfall for the northern inland and into southern QLD which would be follow up falls for these regions after last week's wet weather. But note not much gets to the southeast as compared to GFS which has 100-150mm more precipitation where Euro has 0mm. This is where we need to track the lead system, whether it moves east (like the euro) or southeast (like GFS) which will have significant impacts on the rainfall. Also the Euro has a much weaker front next week compared to GFS.

Euro 12z run - Surface pressure pattern and rainfall distribution - Valid Monday 5th of July 2021.

Note the stark difference in the movement of the low later this week with the trough dragged with Euro adopting an easterly track of the system keeping the southern inland of NSW drier with only patchy rainfall and no low off the southeast of NSW means no rainfall getting into the southeast inland. So clearly there are some divergence in modelling which has consequences in rainfall forecasting.

Just to recap on that low pressure track between the models - it will impact rainfall. In these situations, sometimes the truth lay somewhere in the middle, but ultimately we will have to wait for the trough to lift out of WA first by mid week and see how that looks as it passes through SA and how the moisture streams in from the north ahead of this system.

More weather details and an update on this feature this afternoon. There will be some rainfall later this week, but who gets what remains to be seen. We have four full dry days to get through ahead of this rainfall and then cold snap next week.

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