The weather is variable at the moment with troughs and high levels of moisture rolling through the country leading to fairly active conditions and the potential for severe weather.

We have already seen one very robust rainfall event for the west of NSW produce 2-3 months worth of rainfall, some of that rainfall a little more generous over the central parts of the state ahead of what models have suggested, so once again the moisture content highlighting the prospect of further heavy rainfall is on the way this weekend with another trough and front.

Even Thursday and ahead of the front on Friday, the showers and thunderstorms will still be about the state, mainly west of the divide, with a few showers along the coast. But it will be along the front and trough that sweeps through on Saturday we find heavy rain and thunderstorms become a feature for a good chunk of the state.

The bulk of the heaviest rainfall looks to be found over the southern and central areas with patchier falls over western and northern areas. Some places in the south could see a months worth of rainfall from this event in itself.

All of the weather should contract northeast Sunday and remain up there early next week with a lingering trough.

A mostly dry and cooler start to next week is expected with ridging but I am keeping an eye on the trough forming over QLD and onshore winds returning and another trough and front approaching the southeast mid next week.

Lets take a look


Rainfall Next 10 Days

Rainfall is forecast to be above average for the coming period once again, thanks to a deepening trough and front passing through a very moist airmass during Saturday. We do have lingering areas of rain tonight and some scattering of showers and storms between now and the next system, but the bulk of the rainfall is expected at this time during Saturday morning and clearing Sunday morning over the east. Showers may return for coastal areas during Sunday through next week with onshore easterly winds. These will be more scattered over the northeast. Then we may start to see the influence of a trough over QLD dipping back into northern NSW with storms returning early next week. We could also see another band of rain and storms develop with a front passing through the southeast next week. There is some chance this system combines with moisture moving in via the easterly winds to bring up rainfall chances once again over large areas of the nation including the east. So there is some conjecture in all things forecasting next week over the state.

Rainfall stacking up on the windward slopes of the Great Dividing Range will lead to widespread falls exceeding the average in the eastern Riverina, Southwest Slopes and possibly extending north to Orange and south to Cooma. The bulk of the rainfall falls Saturday. This will be the focus of the most widespread rainfall. Elsewhere, near season rainfall expectations exist so no charts required.

Thunderstorm Forecast Thursday

Thunderstorms are forecast to emerge during the afternoon and evening with thunderstorms not likely to be severe at this time, the dynamics are poor, but some storms could produce moderate rainfall and gusty winds.

Severe Weather Watch - Severe Thunderstorms.

Thunderstorms are forecast to emerge over SA during Friday morning before becoming more widespread as a front and pre frontal trough move into VIC and NSW. Some of the thunderstorms on the trough in NSW could lead to damaging winds and heavy rainfall, that will be followed by the frontal passage with a band of rain with further storm activity.

MEDIUM TERM - May 5th- 12th 2022

Rainfall Anomalies

The rainfall bias has shifted to the east in recent broader guidance, given that we are seeing more drier and cooler air sweep the country. I am suggesting rainfall will be more aggressive over northern and eastern areas of the nation with the SAM tending back positive and with the lingering moisture courtesy of the lingering La Nina, the potential for a rainband to form in the north and east is quite likely. The west and remainder of the south seeing seasonal rainfall expectations. But the door is open for moisture to sweep south and southwest into these areas as well so watch closely.

Temperature Anomalies

A much colder signal has been triggered on the models with all in agreement we could see some quite fresh air being transported behind a strong cold front mid next week leading to the first chance of snowfalls on the mainland and the chance of frost for southern Ag areas of the nation so growers beware. The only thing offsetting the risk of severe frosts is that the SSTs around the nation are above normal and we do have a positive SAM phase unfolding in the east so while watching trends closely, there may be the chance some frost issues we could be talking about in around a week's time for the medium term.

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

The pattern remains largely unchanged for the nation as we track the next major weather maker into the southeast and east this weekend. That could produce severe weather as outlined in the video. The trough may linger over eastern areas of the nation and combine with moisture in the onshore winds to see more rain develop for eastern QLD and NSW. The northern tropics are forecast to be unsettled and more humid than normal with the risk of showers and thunderstorms developing most afternoons. Over southern parts of WA, the next front comes through tomorrow but the next major front is forecast on Monday night through Tuesday bringing that colder shift to the southwest with drier air. The front and trough then run across the southern parts of the country with the chance of widespread showers and gusty winds coming into SA mid next week and then over the southeast and eastern parts of the country. This system could form into a major low pressure system over southern and southeast/east areas of the country but the forecast confidence is low. Also watching the moisture in the tropics into the medium term which could turn south and southeast through the nation lifting rainfall chances once again through the medium term with higher humidity also spreading south and east. The weather supportive of below average day time temperatures for the west, warmer over the north.

00Z GFS - Precipitable Water Values - Next 2 Weeks

Moisture remains deep and elevated over the east hence the cold rain today for many and really the cold rainy weather since about Saturday. The first system is weakening but leaves a trail of moisture behind it, laying in wait for the next system to slam into it on Friday leading to more widespread rainfall. Some locally heavy rainfall is possible as is some flooding for parts of the southeast if widespread heavy rainfall eventuates. The drier southerly flow will move through southern parts of the nation but struggle to push further north. The northern tropics and much of the east will remain in humid air through much of the outlook with onshore winds via the new high ridging through southern areas, and the deeper northeast flow still bringing in above average moisture values over tropical areas. Watching the Indian Ocean into the medium term as outlined today, this could lead to more robust rainfall developing through the medium term.

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 - this forecast output from the GFS will change dramatically in the coming days. Rely on the next 3 days of data probably being something worth betting on, the rest is looking low confidence.

The next update is due out at 8am EST on Thursday. Have a great evening.

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