SA - RAIN AND STORMS OVER THE NORTHEAST SPREADING SOUTH - FRONT TO COME FRIDAY WITH SOME RAIN SOUTH.

The weather is all over the shop for SA, with moisture diverting across the country with a moisture plume heading through eastern districts through QLD and into NSW with a strong upper-level disturbance.


Another upper level trough is forming offshore WA with this trough tapping into moisture coming out of the Indian Ocean and TC Karim which is expected to weaken below cyclone strength, but propel moisture right across the nation.


Unfortunately it does appear that SA sits in between two systems, but light to moderate rainfall over the northeast and east, and coming into the far west later this week is possible. For Ag Areas, the Goyder's Line is full force and highlights this zone quite clearly this week.


While most areas should see some rainfall, the rainfall won't be especially heavy. Temperatures are mild to warm for this time of year and rather humid with the easterly winds forecast to turn northerly ahead of the front.


Now as we track into tomorrow, we will have rainfall moving southwards down the eastern border with some OK falls up in the northeast, could exceed 30mm in remote areas. Up to 10mm further south to areas bordering NSW and VIC. That could clip the Riverlands and Murrylands.


The weather is forecast to clear east on Thursday, but a band of rain will then enter into western districts with a trough and cold front moving east. This band will sadly fall apart as the dynamics start to weaken, though a low will form over the Bight. This low will disrupt the band of rain moving eastwards and pull it south, so by the time it reaches the Ag Areas, we will see rainfall totals become light and patchy.


The band will once again thicken up over VIC and NSW as is typical, where moisture is deeper. Once again, the weather is weather, it is not personal.


More moisture over the northwest of the nation could be drawn southeast into WA and may feed across the state later next week.


Let's take a look

FORECAST

Rainfall Next 10 Days

As mentioned we sit in between all the heavy rainfall events with the rainfall over the northeast offering the better totals for now, but falling over remote areas. Patchy falls will run down the NSW border and into the Riverlands and Murrylands with the potential for maybe 5mm up to 10mm. These events are tricky to forecast ahead of time, but watch the rainfall trends via radar closely tomorrow. The remainder of the southern Ag Areas should be cloudy but mostly dry for now. The rain out west through WA from Wednesday night through Thursday will spread eastwards and reach the far west later Thursday and move along the southern coastal areas on Friday with a low forming offshore. Light falls and windy weather can be expected for southern Ag areas with northern Ag areas possibly remaining dry with this feature. The rainfall reaches the Upper and Lower SE through Friday afternoon into Saturday with the chance of a moderate burst of rainfall as the system reaches the moisture left behind from the current event over the east. Another system may move into the southeast during Saturday night with light falls for the southern coastline and moderate rainfall chances for the Upper and Lower SE with this system before conditions dry into next week with high pressure.

Southeast Districts

Note the rainfall could be heavier as we move towards the Riverlands tomorrow but I am not convinced of it. The rainfall coming through with two fronts for the southeast, one on Friday and another on Saturday with moderate rainfall chances on both but nothing too heavy.

Riverlands and Murrylands.

Rainfall is tricky to forecast, I am shifting the heavier rainfall axis into NSW and VIC but it could swing back, and a deviation of 50km is all it takes to bring 8-15mm for the region tomorrow into Thursday ahead of the front approaching from Friday. But overall the rainfall likely patchy and anything more than what is advertised here is a bonus.

Southern Agricultural Areas

The rainfall sits to the west and east, with more promise for these regions, but timing goes against the higher rainfall chances sweeping through the Southern Ag areas, but this can change on a dime. There is more rainfall next week coming through WA, but the weather is expected to remain fairly active in the medium term meaning we could see further rainfall opportunities.

Thunderstorm Forecast Wednesday

Thunderstorms are forecast to develop further over the northeast tonight with that thunderstorm activity spreading south and east of Moomba overnight but weakening as they do. There is a risk of flash flooding with storms over the far northeast.

Flash Flood Risk Wednesday

Flash flooding remains a very high chance over the border in QLD but it could clip the far northeast during the overnight hours and into Wednesday before the risk clears east during Thursday.

Severe Weather Watch

The severe weather risk is largely unchanged as we track a deep upper low over northern areas today and into the northeast tomorrow. This will be where the dynamics support thunderstorm development, wind profiles and moisture content also supportive of severe weather. The risk should contract east during Thursday and Friday.

MEDIUM TERM - May 17th-24th 2022

Rainfall Anomalies

Rainfall signals for the northwest of the nation are increasing in response to deep moisture being propelled through the jet stream leading to areas of rain and thunderstorms becoming more widespread for WA. This moisture will spread throughout the nation, but the lack of strong trigger means that rainfall totals should be lighter through SA and into the southeast, however this could change if frontal weather is more in phase. Over the east, the increasing signals of a positive SAM phase developing through the coming week, this may lead to more above average rainfall for the eastern third of NSW and QLD. The risk of above average rainfall is higher over in the west this time around.

Temperature Anomalies

No change to the guide from yesterday with a warmer bias over the north with excess humidity in place leading to the chance of dry season showers. Cooler bias over in the southwest and west with persistent cloud cover. The warmer bias in the east is conditional and is based upon higher moisture levels leading to above average overnights and daytime temperatures, especially if the weather is drier than forecast.

DATA - Refer to video for more information and the model comparison and context about all the forecast products you see from me.


00Z GFS - Surface Pressure Pattern and Rainfall Distribution - Next 2 Weeks

More details can be found in the video at the top of the page but I will point out that the weather is forecast to turn more active over the coming days as advertised and the latest risks discussed there. The weather over the west also becoming more active in the coming days with a strong cold front moving through. Then that system could be moving through southern and southeast areas of the country. This system will help knock out the high moisture and severe weather risks over the east by the weekend and cooler weather resumes and a more seasonal spread of temperatures and rainfall can be expected next week. The focus of the wettest weather still looms over the eastern third of QLD and NSW in the medium term but more interest from me is in the west of the country, with a deeper moisture plume coming through the jet stream into the western and central areas of the country which could lift rainfall chances across the nation, WA, SA and VIC could fair better in this scenario.

00Z GFS - Precipitable Water Values - Next 2 Weeks

Widespread above average moisture levels are currently in place across much of the nation and entering the west of the country. It won't be until we see the western system move east, that it will help to knock out the deep moisture over the east and contract it northwards and then clears it away. Then we watch the persistent influx of moisture from the Indian Ocean and see whether that has some major impacts on rainfall rates over the west, southern and southeast of the nation as we move through into next week and the medium term. There are some weak rumblings for a large-scale rain event in the east which has been popping up on some models into the 21st onwards but I am not convinced of that just yet.

00Z GFS - Rainfall Accumulation - Next 10 Days

Refer to the video for more context and analysis

00Z CMC - Rainfall Accumulation - Next 10 Days

Refer to the video for more context and analysis

00Z GFS - Rainfall Accumulation - Next 2 Weeks

Refer to the video for more context and analysis

A closer look in - the rainfall projections are very tricky tonight with the rainfall shield from NSW clipping the region, but heaviest falls could stay along the border. Light falls in the short term as forecast with frontal weather remains the same and we could see better rainfall odds in the medium term. Keep watching.

More coming up from 9pm EDT with a look at the models and rainfall, I will only share information that is in reasonable agreement as too much is too confusing and I only want to share what is plausible at this time, so stay tuned for that.


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