The main weather action in the nation is over Southeast Australia with a upper low and trough combining with onshore winds to bring widespread rain and thunder to the region from tomorrow.

We can already track the rotation on the front that is passing through southeast Australia this evening with patchy rain and thunderstorms in progress over northern and eastern Victoria and southern NSW.

The activity is spreading east overnight, with light to moderate falls expected.

Satellite picture valid May 10th 2021 at 5pm EST.

By tomorrow, the upper low should be positioned between Griffith and Wagga Wagga and meandering to the east slowly. A new trough on the southern flank of this upper low will become the focus for the rainfall redeveloping over Gippsland and the SE inland of NSW where rainfall will lift north slowly tomorrow and become heavy at times. With the upper low and trough moving slowly, rainfall will remain persistent into Wednesday.

Widespread showers near and east and south of the upper low over the ACT, Southern Highlands, Tablelands and Snowy Monaro may see some areas receive 20-30mm out of this event.

Thunderstorms also have the chance of producing large amounts of small hail.

An upper low will be drifting into the region this evening and be slowing moving overnight into Tuesday. Thunderstorms over central and southern inland districts will continue overnight and into Tuesday near this circulation. Large amounts of small hail are possible with stronger storms, but they will be isolated

Hail risk forecast for Tuesday May 11th 2021.

Low = 5-30% Moderate = 30-50% High = 50-80% Very High = 80 -95%

Within 25km of a given point

During the afternoon thunderstorms will then develop over eastern districts, with the severe thunderstorms possible across the broad area of red and dark red shading. All modes of severe weather is possible in this region.

Damaging Winds Forecast - Tuesday May 11th 2021

Low = 5-30% Moderate = 30-50% High = 50-80% Very High = 80 -95%

Within 25km of a given point

Thunderstorms are possible during the afternoon and evening about the South Coast and Illawarra with some storms producing heavy rainfall and small hail. Flash flooding is possible with the slow movement and training of thunderstorms over the same region.

Flash Flood Risk - Tuesday May 11th 2021.

Low = 5-30% Moderate = 30-50% High = 50-80% Very High = 80 -95%

Within 25km of a given point.

Thunderstorm Forecast - Tuesday 11th May.

8/10 or 80% chance of thunderstorms forming within 25km of a given point during Tuesday. The risk tapers down 10% down the radial where yellow is 50% and white is 10%.

Just because you are shaded in does not mean you are guaranteed a thunderstorm.

All that convection will begin to wrap back into the southeast of NSW and eastern Victoria during Tuesday afternoon and evening and possibly along the Otway Ranges in Central Victoria where onshore winds run up the mountains there (like the northern rivers of NSW) to produce widespread heavy showers.

Flash flooding is possible about the SE of NSW during the afternoon with areas of rainfall where training thunderstorms and showers could see rainfall rates exceed 50mm/hr.

Rainfall totals could exceed 100-200mm in the region from Narooma south to Eden and extend inland to Bombala and over the border into Gelantipy and Combienbar in Victoria with minor flooding possible. Catchments are wet in this region.

Rainfall forecast for the next 4 days - Weather Matters. Valid May 11th 2021.

All the activity clears out thanks to a front which will bump the upper low out and produce a more zonal flow over the region, drying out the atmosphere and pushing the rainfall chances back to southern and mountain Victoria in a southwest flow, so the weekend looking much drier for NSW and southeast VIC.

Upper level flow pattern at 18000ft shows that upper low being shoved out by a strong front during Thursday and Friday. Will keep an eye on the shot of cold air that comes up behind it for east coast low potential, but for now I will keep it dry this weekend.

More analysis can be found through the forums and on the comments on this post. Keep the conversation going on the forums and let me know what is happening on the ground.

Need more tailored information? email me at karllijnders@weathermatters.org