On Wednesday into Thursday we have a huge weather system bringing rain to the west, affecting all parts from the Pilbara through to the south coast.
Showers, tending to areas of widespread steady rain, and embedded thunderstorms. Any storm has the potential to bring heavy falls to those directly underneath.
This system affects so much of the west, thanks to two key ingredients: broad, slow moving instability and a feed of tropical moisture. Both of these are working together to spread rain over a huge area.
In NSW there is another low pressure system, but this one is well off the coast on its way to New Zealand. This distance means that only the coastal fringe feels the effects, with a burst of cold showers, gusty winds and hazardous surf. The rain dries up as it heads over the ranges into the west.
The southeast had a cold front on Tuesday, without any connection to tropical moisture - so it brought cold showers, and reasonable falls near the coast, but hardly anything (once again) inland. We need a slow moving low, and a connection to tropical moisture to make a difference here.
In great news, that is exactly what is on the horizon!
The big weather system from the west is heading eastwards. Likely to begin in the southeast on Friday and continue through the weekend and well into next week.
It will be made up of a few low pressure centres (letting it linger longer), significant instability and a fetch of Antarctic air (letting it bring good snowfalls to the alps, beginning the snowpack that will hopefully be added to during the season, then turn into melt at the end and spread through the river systems) - and, best of all, a connection to tropical moisture.
This tropical connection ensures that for those in the path of the lows, there are significant rainfalls on the way.
A complex system like this can be difficult to pinpoint the areas that will do the best, as movement just a little to the east or west can make a big difference in rainfall for those nearby. Where a low centre sits can be the difference of 50 to even 100 mm of rain - with big falls for those in the sweet spot, and hardly anything for those in the rain shadow.
But overall, this rain system should have a big impact in the southeast, exactly what is needed for many.
