SA - ALL ABOUT THE POTENTIAL AUTUMN BREAK BUILDING IN THE FORECAST THIS WEEKEND ONWARDS

All fingers and toes are crossed that the modelling is not punking us, but we are looking at the potential for reasonable rainfall with moderate to heavy falls and a shift into cooler weather as we approach ANZAC Day, leading to the on time shift in weather conditions across the state.


Some of the patchy rainfall yesterday was welcome in the far east, but it certainly was a miss for many others, as forecast the event developed over the east and deepened in Victoria.


The difference with this system is that the modelling is favouring a trough deepening over the interior of SA and this combining with moisture coming out of the northeast of the country in upper level winds and moisture streaming out of the upper level westerly winds feeding the same trough, creating a fairly ripe environment for widespread rainfall to emerge and spread throughout the state.


With some luck, all Ag Areas could walk away with 20mm which would be welcome, on current guide many would see double that, but for the sake of expectations, lets just keep it calm for a while and focus on the systems evolution as that will dictate rainfall forecasts.


So lets take a look where we stand right now and then we can track this week together.

FORECAST

Rainfall Next 10 Days

Patchy rainfall clears east tonight and moves into Victoria and NSW on Tuesday with a drier day returning for much of the state, maybe some lingering light showers for the southeast into mid week. Over the course of the remainder of the week, dry weather is forecast with increasing temperatures over inland areas. Now as we get into the weekend, this is where things begin to shake and bake and we start to see widespread rainfall emerging through forecast modelling over northern areas of the state and surrounding inland areas of adjoining states near a deep trough. This trough is pulling in moisture from multiple ports and could see an Autumn Break unfold with a large rain band developing as the weather begins to shift. Now this trough is likely to be slow moving so where it sets up and how far west it evolves will have a large bearing on rainfall for the Ag Areas across the south and southeast. But it looks promising. Follow up rainfall is looking a better than 50% chance for the state into early May as well.

MEDIUM TERM - April 25th - May 2nd 2022

Deep moisture across the nation looks to spread rainfall and the Autumn Break for many areas. Another moisture surge over northern Australia with a tropical wave passing north of the nation is possible with increased humidity and late season falls for the far north. This moisture too could be drawn south or southeast into the nation lifting rainfall chances. Another wave of low pressure passing through from the south of WA could surge northwards and bring a colder drier airmass towards Australia, which may help to promote another rain band forming in Southern Australia at the end of the period.

Rainfall Anomalies

The anomalies are shifting above average as we move through the period with many areas now leaning towards a wetter bias for the period, thanks to the secondary system on the charts we can see over ANZAC Day and another system lurking out there in early May. Now in pinning down who gets what relating to rainfall totals, that is not possible, but you can clearly see the areas identified as being wetter than normal. And a good chance for many of you.

Temperature Anomalies

Becoming cooler as more rainfall and cloud cover takes over the nation with the warmer than normal weather of this week moving further east and north across the country with a colder shift for the southwest, south and eastern inland quite possible as we move into May. Warmer signal developing for the northwest and west with a persistent easterly flow as the east sits under the positive SAM influence leading to more cloud and rainfall.

DATA - Refer to the video for further information and it is critical to keep check of the data sets to understand where the next major weather events are emerging from outside of this period. It may be quiet now but I am all about preparation and ensuring that information is shared with you as soon as it is available.


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

A lot more in the run down in the video but there are 2-3 events to watch in the forecast period that offer some interest for vast areas of the nation. The issue will be the timing, scale and intensity of each of these and because it is a high amplitude pattern, the forecasts will bounce around furiously!

00Z GFS - Precipitable Water Values - Next 2 Weeks

The PW values are really elevated through this period which is not uncommon but what you will find with the extra moisture content means more efficient rainfall events with higher intensity rainfall with thunderstorms and if we do end up with severe weather, flooding would be a feature. Inland areas need to be on alert and follow modelling trends as we go along.

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 Euro - 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 - rain in the short term more widespread east of here, but keep an eye on the follow up rain event from next week! That is the one to watch.

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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