RAIN TO AMPLIFY OVER NSW AND VICTORIA AS A TROUGH ARRIVES MID WEEK.

A large scale low pressure system with a trough and multiple shortwaves are expected to bring widespread rain and a few storms to the region from mid week and then a cold showery airmass into Thursday and Friday.


A large cloud band has developed over western parts of the nation today, as forecast, which is continuing to move eastwards through the state and into western NT and SA this evening.


That cloud band will move through much of SA during Wednesday before falling apart a little bit during Wednesday afternoon over western areas of NSW and QLD. Some rain may develop in organised batches with clusters of showers and thunderstorms breaking out in response to the trough running into moisture coming in on northeast winds that will be in place over the east coast during Tuesday and Wednesday.


Rainfall for the next 10 days - Valid Monday 21st of June 2021.

Widespread rainfall from the lead system to favour areas on an west or north of the divide through the southeast and coastal areas with the low pressure system rolling through west to east.


Rainfall will be light to moderate for the most part for Victoria and NSW, but heavier falls of rain are possible over the Great Dividing Range in NSW and on the northern slopes in Victoria with falls in excess of 40mm possible in VIC and southeast NSW. Not much snow is expected this week with this feature.


The rain will continue to contract through NSW during Thursday, clearing the northeast later in the day or early Friday as the parent low attached begins to wash out over VIC and upper heights begin to recover and ridging develops for the weekend clearing skies.


This will be a widespread rainfall event, but not everyone is expected to see heavy rainfall. It is a typical winter system with a large cloud band coming in from the northwest linking up with a low pressure system to propel a multi day rainfall event. The totals should be somewhere between 10-25mm for most with scattering of areas over higher ground getting 25-40mm.


Typical weather pattern with that infeed of moisture feeding the jet stream and propelling moisture from the northwest. Limited moisture being drawn in from the northeast winds over QLD and NSW will help to reinvigorate the rain band as it moves over eastern areas as you can see below.

Rain increasing in response to the better moisture laying over the eastern inland, with the coverage and intensity increasing over areas west of the divide in NSW and north of the divide in VIC.

Low hangs back over SA meaning the rain band becomes slow moving over NSW and southern QLD with areas here looking to get the best of it, but a dry slot opens up over western NSW and eastern SA, meaning the sinking air motion with breezy conditions leading to cold and fair weather with partly cloudy skies.

Low washes out, the residual moisture is now dissolving along the trough over eastern NSW and clearing east later as high pressure moves into central Australia. Previously we have seen the low lasting in form as it crossed through VIC allowing rainfall to be more widespread for QLD, but this looks less likely now and forecast charts will be updated accordingly.


The weather clears this weekend before another rain event develops over WA with another round of cold fronts sweeping into the southwest of the region. Widespread rainfall there could be heavy at times. Will be watching the Indian Ocean as to whether that can send in another shot of moisture into the cold fronts moving east bound, combining to bring another large cloud band and rainfall.

Precipitable Water Forecast - GFS next 2 weeks - Valid Monday June 21st 2021.

Widespread moisture advection through to the southeast to continue as we go into late this month and early July, boding well for follow up rainfall across the nation as we track deeper into winter, in line with the Indian Ocean becoming more favourable for widespread rainfall into late winter and early spring.

The impact of the Indian Ocean Dipole - A general rule for winter and spring. Not always the case but a fair representation of what one would expect in these conditions when cold fronts are more active.

There are signals into the future that this will be quite possible for more above average rainfall, which would be great for areas that have continued to miss out.


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