Above: A trough precedes the cold front that marks the leading edge of cold air surging into southeastern states. These surface charts are for 4am, 10am, 4pm and 10pm. BoM.

Above: IR satellite hourly images (1200, 1700, 1900, 2100, 2300 missing). While cold air spirals around the Low onto the SA coast, cloud rapidly develops over western NSW in uplift ahead of the front and streams SE into VIC and TAS.Weatherzone, BoM. (GMS-5 backup with GOES-9 operated by the joint effort of JMA and US NOAA NESDIS over the Western Pacific) Below: Composite radar/lightning tracker approximately hourly through to 4am Thursday shows the development, movement and eventual dissipation of the rain area. Note the intensification and duration over NE VIC. Weatherzone

A major rainband gave southern NSW and a large part of VIC their best rainfall in over two years today. At least 10 locations broke 24-hour rainfall records for July, and flooding commenced in northeastern VIC rivers.

A tongue of very moist warm air has been dragged south from QLD over the past couple of days in strong northerlies ahead of the vigorous cold front that moved through WA on Monday and Tuesday. With temperatures behind the front some 14C lower than ahead of it, major uplift occurred as the dense air undercut the warm, and topographic uplift further enhanced the rainfall over the NE VIC highlands.

As the map above shows, more than 25mm fell across central and northeastern VIC and the NSW Riverina, with the mountainous eastern parts of VIC recording from 50 to 106.8mm at Lake William Hovell Dam, 40km NE of Mansfield. Heavy rain also fell on the TAS North Coast, with 118.4mm recorded on Mt Barrow, 40km east of Launceston.

Many places broke July one-day rainfall records for the 24 hour period to 9am Thursday. Most noteworthy was Lake Eildon's 101.2mm, which was only 0.1mm shy of their all-time record for any month in 114 years of rainfall measurements. Euroa (61.0mm) and Seymour (59.6mm) both had their wettest July days in 115 years of record. Other significant records were toppled at Narrandera NSW, and Kyabram, Tatura and Mangalore VIC. A full list of heavy falls and new records is given in the National Extremes for 24 July.

Despite dry catchments, the rain was heavy enough to cause rapid stream rises. Seven Creeks and Castle Creek, which drain off the Strathbogie Ranges to Euroa, were in minor flood by early evening, and the Mitta Mitta upstream of Dartmouth Dam was in moderate flood by around midnight. See further flood reports on 24 July. The rain and the runoff were especially welcome to central VIC farmers, filling empty farm dams and bringing 30 to 40mm to grain crops and in the major potato growing areas around Daylesford and Ballan. The eastern and northern Mallee, which missed early season falls, recorded 20 to 30mm, while the Goulburn Valley and northeast VIC recorded 50 to 100mm.

Despite heavy rain in much of the state, runoff was not enough to ease the threat of water restrictions. Melbourne Water announced on 30 July that stage 2 water restrictions would be introduces from 1 August. Runoff had pushed storages from just over 40% to 41.6% during the week, below the August trigger level that would have averted restrictions. Melbourne Water's CEO Brian Bayley said "We are still in the midst of seven-year drought. Rain over one week is fantastic but it's not going to help our storages recover to the point where would like them to be."

Rain in NSW was mostly limited to the Riverina, most of which recorded over 25mm. 10 to 15mm of rain around Broken Hill closed the road to Tibooburra and the Tibooburra - White Cliffs and Wilcannia - Menindee Roads.

Strong, squally winds ahead of the front produced widespread dust storms, unusual for July. The wind gusted to 117km/h at Wagga and 100km/h at Condobolin in the early evening as the front passed through. A huge dust storm in central western NSW brought down trees and power lines, leaving Cobar, Dubbo, Parkes and Canowindra without power. Forbes experienced its first winter dust storm in 60 years according to press reports. Dust storms or raised dust were also reported from Cowra, Wagga, Cootamundra, Quandialla, Wyalong and Lake Cargelligo in NSW, Arltunga and Rabbit Flat in the NT, and Mt Isa, Urandangie, Bedourie and Thargomindah in western QLD. Overnight into Thursday, thunderstorms with strong wind gusts brought down trees and closed roads around Tamworth, Quirindi and Attunga. Downed trees and powerlines closed roads east of Bathurst and knocked out power at Oberon. Hurricane force winds scoured the Victorian Alps in the northerlies ahead of the front, with Mt Hotham summit reporting a top gust of 145km/h, Mt Buller 119 and Falls Creek 115.

The cause of the strong, squally winds was the dramatic temperature contrast across the front. Overnight minimum temperatures in southwest QLD and western NSW were particularly noteworthy, with Thargomindah 12.8 above average and Condobolin Ag Station 12.0 above. Cobar's minimum of 15.8 was 10.8 above, and was the warmest July night on record for the town.

There were radio reports of light snow in SA overnight into Thursday. A light dusting was reported on Mt Remarkable, altitude 965m, southeast of Port Augusta. Snow, falling but not settling, was reported from higher country around Clare in the central north. Brief light snow fell in the Adelaide Hills near Crafar, and light hail showers were extensive across the southeast of the state during the day.