SA - SEVERE WEATHER DEVELOPING LATER THIS WEEK.

No change in the overall guidance, but what many of you weather weenies are seeing is fluctuations in the rainfall guide from model to model, from run to run, which is to be expected under such a dynamic and complex synoptic pattern.


Thunderstorms are expected to fuel the majority of the heavy rainfall and this leads to flash and riverine flooding for many areas of the Outback which may stretch into the western and northern Agricultural areas from Friday through the weekend.


While this is going on, the eastern Agricultural Areas will remain hot, mostly fine and very humid in a northeast flow, waiting for the stalled trough to start moving southeast and east.


That will take place later this weekend into early next week, as another wave of low pressure forms on the trough and we see a low pressure system form somewhere along the trough, and where that forms will determine where the heavy rainfall develops as the cooler drier southerly comes in around Australia Day


So finally, some active wet weather on the way.

FORECAST

Rainfall Next 10 Days

The weather drying out though remaining humid over much of the state inland of the coast in a broad easterly flow. The moisture is holding in place, waiting to be lifted by a trough that is expected to form in response to an upper disturbance that will set up over central SA. This will be the focus of the wet weather through the end of the week into the weekend and next week. Areas of heavy rainfall and flash flooding is a reasonable chance under this guide from the models. Some areas could see not only their Summer rainfall in a sitting but also 6 months worth of rainfall in some Outback areas. This heavy rainfall potential moves east later in the weekend into next week as the trough gets a move along by a new ridge over WA. So widespread rainfall to be with us over Australia Day but clearing thereafter with a southerly flow sweeping the moisture north and east.

Severe Weather Watch - Friday through Tuesday

Severe weather is expected to develop with a significant storm outbreak developing from Thursday and lasting through to early next week. The heaviest impacts are expected to be over the Eyre Peninsula through to the Northwest Pastoral District but it is likely to spread through to the remainder of the Agricultural Areas during the weekend and into next week with heavy rainfall and damaging winds the main concerns at this time. Riverine flooding and ponding over the outback is likely as well. The weather will clear east by Australia Day at this time.

Flood Watch - Friday through Tuesday

Significant thunderstorm activity for a number of days over the same areas could lead to flooding for Outback areas of SA and extending into the Eyre Peninsula and possibly the remainder of the eastern districts, depending on the trough evolution and low pressure development. At this time the higher risk is for areas over the EP and points north.

DATA - More information can be found in the video with the daily breakdown nationally for the short and medium term.


00Z GFS - Surface Pressure Pattern and Rainfall Distribution - Next 16 Days

The modelling will chop and change as we go along, it is high amplitude, dynamic and this lends itself to being volatile. So use this as a guide. The takeaway is, humid, more unsettled than normal, wetter than normal for many areas away from the SWLD of WA and severe weather chances increasing for northern, central and eastern areas of the nation. Be aware that tropical systems up north will change you rainfall odds as well from run to run.

00Z GFS - Precipitable Water Values - Next 16 Days

I don't think I have seen it as moist across the nation since the Brisbane Floods of 10 years ago. So this is a dangerous atmosphere and with this main ingredient for rainfall running at near record levels, that means all we need is deep instability to produce heavy rainfall. With the slack upper level wind profile, that means areas slated in for heavy rainfall and thunderstorms could see that persist for multiple days increasing flood risks. So there is a lot of concern from me in relation to each low pressure system that moves across the nation.

00Z GFS - Rainfall Accumulation - Next 10 Days

More information can be found in the video.

00Z CMC - Rainfall Accumulation - Next 10 Days

More information can be found in the video.

00Z GFS - Rainfall Accumulation - Next 16 Days

More information can be found in the video.

A closer look in. In areas that are seeing the mottled and uneven rainfall guide here, be aware that with the moisture content at near record levels in some locations, that could result in some areas recording 50-100mm in an hour from slow moving thunderstorms, so this is a guide!

More details coming up this evening looking at all things modelling and rainfall, especially important information for those staring down a lot of moisture and rainfall forecast in the coming week.

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