A nasty spell of weather is expected to unfold from tomorrow with a large amount of tropical moisture being drawn into the state, you can feel it already today with the air becoming thicker and even though temperatures are cool in the east, you can notice the change in conditions. Showers and thunderstorms are forecast to break out this afternoon and evening over the western districts and these will move east overnight.
Areas of rain likely to kick off Wednesday, with a thick cloud cover. The areas of rain likely to be more widespread and moderate over the southern districts through to the ACT with lighter falls to the southeast. During the afternoon and evening, another batch of thunderstorms will develop and these will likely turn severe with heavy rainfall leading to flash flooding the main risk along with damaging winds.
The convection that fires over western parts of the state will be where the rain and thunderstorm band that brings the severe weather risk begins. The rain ahead of that tonight and tomorrow morning is light to moderate and not expected to be severe.
Thursday and Friday. Areas of heavy rain over the eastern 2/3rds of the state with some areas recording 1-2 months worth of rainfall. The west will see easing conditions later Thursday and then the southern areas over Friday. The rain may persist over the east, through central and northeast areas during the weekend, depending on where or IF the upper low stalls out.
Next week, models have been hinting at the moisture recycling around a high that will zip through to the south of the state and propel the moisture back west through the state and a trough is likely to meet up with this moisture to reignite more rain and thunderstorm potential. The timing and scale of this feature is way too hard to pin down so just be aware more potential for follow up rain is possible next week.
Lets take a look
Rainfall Next 10 Days
Rainfall is expected to become more widespread during Wednesday and tend moderate to heavy with a new batch of thunderstorms, which is expected to form during Wednesday afternoon or evening. Thursday and Friday, the rain will continue to be widespread but the weather is anticipated to ease from the southwest during Thursday and Friday and some clearance for southern districts towards the ACT by Friday into Saturday is likely. The moisture and rainfall may decrease in intensity but stick around over the weekend into next week for northern and eastern parts of the state. Central areas also on the edge of this activity. Next week more showers and thunderstorms are forecast to return with another trough deepening through the left over moisture, which may increase further. For now we will focus on one system and I will take a look at this follow up potential in the update at 9pm. I will issue regional charts when confidence increases so stay tuned to updates. Keeping it broad helps you see the regional impacts of heavy rainfall in catchments closer by.
Thunderstorm Forecast Wednesday
Thunderstorms are currently developing over the western districts tonight and they will continue overnight and move east into the Riverina and Southwest Slopes during the morning, elevated and non severe. Further thunderstorms will develop during Wednesday in a broad band from the north down through central areas and back into the southwest where they may become severe. Heavy rainfall leading to flash flooding as mentioned through most of this week the main concern along with a few storms producing damaging winds. This activity will progress eastwards to the slopes during the evening but more likely flattening out into an area of rain with moderate to heavy falls.
Flash Flood Risk Wednesday
Flash flooding is a high chance with any thunderstorm activity that forms throughout the region identified with copious amounts of tropical air being lifted by a deepening trough and developing low pressure system back in SA. The risk translates east during the evening.
Damaging Winds Risk Wednesday
Damaging winds a moderate risk along the leading edge of the thunderstorm activity that forms. If a squall line develops then the risk is elevated but that is a conditional risk. At this stage rainfall is more of a concern.
Riverine Flood Risk This Week
No change to the guide at this time, be weather aware and pay attention to the official flood warnings/watches in the coming days.
DATA - You can find the GFS in the video for comparison.
12Z Euro Surface Pressure Pattern and Rainfall Distribution - Next 10 Days
The Euro is continuing with the wild weather for the next 3 days. What happens beyond then? So we have fine and hot weather for the west right into next week, the tropics are turning more active but routine weather anticipated and SA generally turns dry and warmer. The east is where the weather remains unsettled through the weekend and into next week with more rain and thunderstorms. Some of the other global models suggest another major rainfall event next week for VIC, NSW and QLD which could pose more flooding threats and really finish off harvest for many. That will be a feature of the update at 9pm.
12z Euro Precipitable Water Values - Next 10 Days
The values are elevated over large areas tonight but note the moisture does get pushed east, however the moisture hangs up over the eastern states and this is where rainfall and thunderstorm activity may remain in place right throughout the outlook period which may continue the flood threat. The tropics also very soupy with waves passing through with much better chance of more widespread rainfall. The west, under a decent period of dry air and hot weather, but the humidity could be drawn into the developing west coast trough next week leading to showers and thunderstorms developing.
12z Euro Rainfall Accumulation - Next 10 days
Refer to the update at 9pm for more details
A closer look shows some areas over inland NSW could see 150-200mm in spots and up to 400mm over the north coast. Such meso scale forecasts are very tricky to manage ahead of time. BE WEATHER AWARE! YOUR NUMBER WILL VARY! ONE STORM COULD DROP 50-60mm IN AN HOUR!
I am trying to keep the content as easy to navigate as possible as there is a lot going on. More at 9pm.