SA - PATCHY RAIN AND WARM FOR FRIDAY THEN SHOWERS INCREASE WITH A COLDER SHIFT SUNDAY.

The warmer weather continues across the region today with a cloudy sky and areas of patchy rainfall. The rainfall has been light, though a few heavier bursts are possible in random pockets as the cloud band runs through the south and east of the state during the afternoon.

Northern areas will remain largely fine and dry with temperatures well above average.


The weekend will remain warm and mostly dry over the inland, though humidity values are remaining elevated through the weekend, though inactive, it will still produce areas of middle and high level cloud cover.


The moisture then deviates to the southeast as it is picked up by upper level northwest winds which freshen ahead of a cold front that surges northeast. The main dynamics will play out east of SA with showery periods likely along the front with moderate falls along the southeast coastal areas.

The showers drop off in number as the high moves in from the west from Tuesday, a cold dry airmass leading to below average temperatures and the threat of frost.

Lets take a look.


12Z GFS Surface Pressure Pattern for the coming 16 days

The change that we have been tracking most of this week is now starting to move through SA this morning with the front sliding southeast and the moisture hanging back over inland areas, we can see that on the satellite. The weather has improved over in WA behind that system with the long wave moving into the Great Australian Bight. It is from there that we will see the stronger cold front develop from Sunday afternoon and move northeast and east. The weather ahead of that, warm and breezy over much of the east and southeast states. But that comes crashing down with the strong cold front passing through from the west during Sunday afternoon and into Monday. A larger band of rain should cover much of VIC and NSW creeping into QLD with moderate rainfall totals. From next week the models keep the instability in place, but are split on how it unfolds over the eastern states. The west will see a warmer trend before the next batch of cold fronts, but again the models are split on how strong they are and how far north they will be. The tropics sees changeable conditions with the dry and humid air battling it out over the coming fortnight.

12z GFS Rainfall for the coming 16 days

Rainfall largely confined now to the southeast states during the coming weekend into next week with a large cold front passing through. Some indication that there could be some rainfall lingering about parts of the coast and the adjacent inland especially if the cold air lingers over inland NSW and QLD. But beyond the major rainfall event early in the new week, the forecast confidence is much lower. In the medium term which I will cover off later this morning, the west will see further cold fronts passing through this time next week, and humidity over the north may see showers developing next week.

12z GFS Precipitable Water Anomalies next 16 days

PW water hanging back today over parts of SA as the primary front begins to move southeast and leaves the moisture behind. That moisture plays a large part ahead of the next front as the winds turn into the northwest Sunday. The moisture is then dragged into the front as it passes over the southeast states with areas of rain and storms. A dry slab of air will then sweep through the eastern inland on the western face of the low in southerly winds bringing a sharp drop in temperatures. Out west, the drier air will turn more moist as winds turn northwesterly ahead of the next cold front which will offer the next rainfall event this time next week. Over the north the moisture running east to west, looks to be caught in the mid latitude westerly winds in the medium term ahead of cold fronts coming out of the west. Moisture builds further over QLD in onshore winds in the medium term.

12z Euro Surface Pressure Pattern for the coming 10 days

Euro has become more in line with the other global models now, seeing the front sliding off to the southeast this morning. A stronger system developing over the southeast by Monday, now the Euro a little slower, with areas of rainfall slowly moving through the southeast inland of the nation. SA and WA will clear out by early next week with the main frontal weather passing over VIC and NSW. QLD and NT will see continuing onshore winds. The weather is expected to warmer out west ahead of the next few fronts this time next week. How they impact the rest of the nation is determined by how long the low pressure system lingers over the southeast of VIC.

12z Euro Rainfall for the coming 10 days

The patchy rainfall today is expected to pass through over the coming 24hrs from SA, into VIC and southern NSW. Not much in it. Then we will see a larger rainfall event develop over the southeast inland during Monday. Moderate to heavy falls possible over NSW and VIC with that shower activity passing up to southern QLD. Now beyond that system the weather is low confidence with models suggesting that the frontal weather over in WA will push off the low in the Tasman faster but other modelling keeps the low pressure closer to the east coast with cold air in the upper atmosphere leading to showers over NSW, VIC and southern QLD. But for now the higher confidence is in the weak system today over the east and the stronger feature Monday. More frontal weather next week over WA carries a moderate confidence as does the showery activity over northern parts of Australia.

12z Euro Precipitable Water Values next 10 days

Like the GFS, the moisture hanging back over SA today gets absorbed into the northwest flow and picked up by the strong cold front during Monday bringing areas of rainfall to NSW and VIC with that heavy rainfall potential. Then the moisture is swept into the north by a southerly wind flow. The weather out west, dry and warmer ahead of another pulse of moisture coming in from the northwest mid next week with another front on the approach bringing the better chance of rainfall from mid to late next week. The tropics sees the moisture still coming in along the trade winds with that moisture then running across the Top End and into northern WA.

Rainfall for the next 10 days

The patchy rainfall today will continue to deliver light falls for most of the south today with the moisture hanging back this weekend, again a few spits and spots of rainfall but warm with a lot of cloud is the forecast for now. We have that stronger front that approaches later this weekend with showers increasing. The better rainfall sits over southeast districts and into VIC and NSW. Another set of fronts may approach later next week into the weekend, with the bulk of next week following the front dry and cooler.

I will have a seasonal update for Spring 2021 at lunchtime today.

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