Flash flooding is a distinct possibility in parts of southern Queensland and northern NSW, with more than 100 millimetres a chance by the weekend. Pinpointing where the heaviest rain will occur is no surety but flash flooding is a good chance somewhere in the vicinity of the border ranges. Anywhere from Birdsville to Brisbane to Sydney may also see flash flooding with more than 50mm a possibility. In the last week-or-so moisture has been steadily building to unusually high levels and has already led to significant rain in a destabilizing atmosphere. Developing troughs of low pressure are tapping into the moisture and are also dragging it further south. Widespread rain will reach southern NSW, Victoria, Tasmania and South Australia. Good rain is not unusual in southern states during the winter months but is very uncommon across the interior and north of the country. Ballera in far southwest Queensland has gained about 20mm today, not enough to flood but this is its wettest July day in at least 10 years. Many other locations in Queensland and NSW are likely to pick up their highest July rainfall in decades.