The first severe storm outbreak of the season is expected to unfold from tomorrow through Friday as a trough starts to move through the south. This will likely be the most widespread rainfall event for the state since early July when we had a large cloud band move through.
Thunderstorms could turn severe Wednesday through Friday with moderate to heavy rainfall a good chance after overnight falls of up to 70mm through Central areas. The pattern has begun to shift.
Lets take a look
Rainfall for the next 10 days
Rainfall is largely confined to southern areas where thunderstorms will be rolling through the region. Thunderstorms are likely to drive the heaviest of the rainfall with some areas possibly recording 50-70mm of rainfall while down the road, some locations could record 15-30mm of rainfall. The rainfall will likely remain uneven in distribution. By the weekend, a drier more stable airmass should begin to filter in clearing rainfall chances back up to the tropical north. Over the north, scattered showers and afternoon thunder possible about Cape York from next week and the trade winds should start to freshen next week increasing showers along the coast.
Thunderstorm Forecast Wednesday.
Thunderstorms are expected to redevelop during Wednesday morning, with storms turning severe about the southern and central inland on the spine of the trough. Damaging winds, heavy rainfall leading to flash flooding and large hail are all possible during Wednesday afternoon. A brief isolated tornado is also possible about the far south along the NSW border. The thunderstorm risk continues into Thursday and Friday but will be progressing towards the eastern districts.
Flash Flood Risk Wednesday
Flash flooding due to thunderstorm activity is a moderate to high risk across the southern and central inland along a trough that will slowly move east through Wednesday. Rainfall rates could exceed 100mm/hr which will reduce visibility and see flash flooding develop quite easily on hard ground.
Large Hail Risk Wednesday
Large hail also a moderate risk throughout the afternoon and evening on Wednesday with the strongest thunderstorms along the trough. Not all thunderstorms will produce large hail, however if you are in this region, be prepared for the usual risk of large hail being about. If you live in this region you know what to do and what to look out for.
Damaging Winds Risk Wednesday
Damaging straight line winds are possible on Wednesday afternoon along the trough where thunderstorms develop and points east as they organise in a line and push towards the Darling Downs. Some of the winds could exceed 100km/h. The risk continues into Thursday and Friday.
Tornado Risk Wednesday
A small chance of an isolated tornado during Wednesday afternoon and evening with the most severe thunderstorms, there is a chance of a few supercells, but more likely Thursday and Friday over the southeast.
Euro 00z - Surface Pressure Pattern and Rainfall Distribution - Next 10 days
No real changes from this morning with widespread rainfall over the eastern states dominating with lighter falls back over SA for the coming days. Severe storms bringing wild weather to parts of NSW and QLD in particular. Flooding a concern under the current synoptic guide as discussed in the video for the east. QLD could see there best rainfall since July with the coverage of showers and thunderstorms over a number of days. For western parts of the nation a few showers and storms tomorrow ahead of a stronger front on Friday bringing more widespread rain and strong winds. That system will have a tough time up against the blocking pattern over in the east. It is still likely to bring scattered showers and gales to parts of SA and into VIC, but moisture is way more limited than with this current system. Another system should roll through the southwest of the nation early next week with more showers and storms, that system again tracking eastwards. Over the tropics the weather turning sultry and thundery, though an upper high may suppress activity at times next week.
Euro 00z - Precipitable Water Anomalies - Next 10 days
Again no real shift in the guidance with widespread rainfall developing out of a deep moisture layer that has built via easterly winds since Sunday and another port of mid and upper level moisture rushing in on the northern flank of low pressure in the Bight into the eastern states via the jet stream. Widespread rainfall is starting to occur over the eastern states as a result. The moisture content will stick around until southerly winds sweep the moisture out to sea. Another moisture surge comes south and southeast through the nation bringing another burst of rain to the west near the trough and front. The moisture thins out as it hits a brick wall over the east so rainfall coverage will not be as extensive due to this blocking pattern. Then another surge of moisture is anticipated over the southwest and west of the nation with another system next week, the tropics turn soupy and humid with increasing PW values and perhaps some of that drifting into WA sitting ready for the jet stream to pick up and lift southeast.
Euro 00z - Rainfall Accumulation - Next 10 days
Rainfall unchanged from last night and this morning, your number will vary under thunderstorm activity. The best of it falling over the east and southeas these next few days, before the focus shifts back to SWLD of WA Friday and then that sweeps through the southern states during the weekend and into early next week. Another system may bring more rainfall to the SWLD of WA continuing the trend of above average rainfall for the region this year. The northern tropics remain suppressed so if you are a fan of feeling like you are in Hades, well this weather will be for you.
A closer look in now.
GFS 00z - Rainfall Accumulation - Next 10 days
You can find out more about this chart in the video.
More details to come tonight from 9pm looking at the full model spread and an update on the severe weather potential, IF there are any changes ongoing.