A high pressure ridge that is parked over the southeast is expected to move off the NSW coast over the coming days, with part of the ridge hanging back through inland NSW through SA to another ridge building over WA. This weak subtropical ridge will continue to set up camp over inland SA for the coming 7 days or so, leading to suppressed rainfall chances away from the coastal areas.
Rainfall for the coming 10 days - Valid Monday 28th of June 2021.
The rainfall chances increase as you head further south and southeast through SA and towards the coast, that is largely thanks to a cold front that will move through southeastern parts of the state later Thursday and then set up a unstable southwest flow during Friday and into the weekend.
The front that is due to arrive during Thursday could pack a punch for southeast districts and may as far north as Adelaide across to Minalton and Tumby Bay. These areas could see an organised batch of gusty showers, maybe some thunder as the front rolls through later in the day.
Follow that front, the unstable southwest flow will continue to drive showers during Friday but will likely become more isolated as we track through Saturday as a new high begins to edge in from the west, lower cloud tops and drying the atmosphere.
That high then will control the weather from Sunday through early next week.
Euro 12z run - Valid Monday 28th of June 2021.
Note the vigorous change moving through later this week, however it is not connected to the Indian Ocean moisture source, that is because it is rearing up from a position that it too far east to get any of that deep moisture supply to develop a rainband for the central and eastern parts of the nation. But if you keep watching, at the end of the sequence, the door opens up for another strong front which may bring better rainfall potential outside of this forecast period from the 8th of July onwards for inland areas and then the eastern inland once again.
The signals for rainfall improve through the latter part of the first week of July but more likely into the second week of July for large parts of southern Australia with a stronger sequence of weather. The moisture developing out of the northwest could be deep enough for a sustained rain band, whether it is with the lead system or a follow up event that develops on the back side of the long wave passing through the southern Australia, one of them will bring a better chance of inland rainfall coming through the Ag areas in SA and the Mallee country through to VIC and southwest NSW.
I have posted about the influence of the Indian Ocean becoming more evident as we go through winter and through spring today in another post. We can see the next set of fronts in the medium term starting to bring that moisture back into the nation from the northwest and dragging it southeast, that is the job of the negative IOD and we should expect to see that more as we go forward through July into August and deepen it's influence in Spring.
GFS Precipitable Water Values - Next 2 weeks - Valid Monday 28th of June 2021.
Note towards the end of the run, significant moisture plumes of 25-50mm starting to move through WA into SA. Also note the moisture stuck over QLD through the early part of the viewing period and draped over northern Australia once again, an excellent breeding ground for more rainfall events in the coming months.
GFS Rainfall - Next 2 weeks - Valid Monday 28th of June 2021.
Notice the rain in the east with that anomalous moisture plume and trough working together to produce widespread heavy rainfall throughout the east. And look out west, later in the run, once the east dries out, the rainfall chances return to inland WA spreading south and east. With some luck this will come into SA in the medium term.
Temperature wise, through this period, the overall weather is looking seasonal with nothing brutally cold throughout SA, the coldest air will ride through Thursday night and Friday this week, but be deeper over VIC and through TAS, so it will bypass the region without too much fanfare.
Some of the colder air will be trapped under the high as it moves southeast so the weekend, will be cold and dry for inland areas with a southerly breeze, coastal areas moderated by a little more humidity.
Nights are continuing the trend of being below average through the inland areas and I do suspect frosts will continue for the Flinders district post this event Friday as winds go calm and skies stay clear across the weekend.
Temperature Anomalies - Saturday.
In the wake of the front, cold air damming will occur under the high to bring cold nights with widespread morning frost over the inland.
Temperature Anomalies - Wednesday 7th July.
But the temperatures being below average does not last long, by mid next week a warming trend takes over as the high heads east and I do think we will see a period of warmer than normal weather take over much of Australia including SA for a number of days.
Temperature Anomalies - Tuesday 13th July.
Really warm air developing over the inland areas thanks to a northwest flow and higher humidity values being drawn in via the Indian ocean. That will keep SA warm and the chances of rainfall increasing as a cold front rolls into the warm and humid airmass. That could develop into a dynamic system in the second week of July.
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