Spring is well under way, with stormy skies marking the change of season over parts of New South Wales and Queensland during the next few days. Thunderstorms have already been affecting QLD's central inland since Friday afternoon due to a trough lingering over Australia's east, with substantial falls across the Central Highlands and Coalfields. Rolleston and Emerald both saw their heaviest September falls in almost half a decade, recording 17mm and 16mm respectively in the 24 hours to 9am today. Several places in the district also saw falls in the order of 30-40mm, with as much as 53mm at Humboldt. The trough has already flared up further thunderstorms today across northeastern NSW and southern QLD, with activity likely to become more widespread this afternoon, particularly along the ranges. Sunday will see a lull in thunderstorm frequency as the trough weakens, with only the odd thunderstorm likely over NSW's northern inland. However, a weak low pressure system and trough will encourage unsettled conditions to return from Monday. NSW's northern ranges and south are likely to see the first activity from this system, although it is likely to be fairly isolated. As the system edges east on Tuesday it will gain moisture, causing thunderstorms to become more widespread across eastern NSW and southeast QLD and should be the most thundery day experienced so far this spring across the region. From Wednesday or Thursday, a high pressure ridge will encourage more settled conditions to return across the region.