Sydney commuters could be in for a stormy ride home with thunderstorms predicted, while residents in northern parts of the state face large hail and damaging winds that could even whip into tornadoes.
The Bureau of Meteorology on Monday issued a severe thunderstorm warning for heavy rain, large hailstones and damaging winds for a region stretching from Griffiths in the Riverina all the way up to the Queensland border.
Among locations affected include Armidale, Orange, Mudgee, Gulgong, Tamworth, Gunnedah, Moree, Narrabri, Walgett, Dubbo, Parkes and Lightning Ridge. (See bureau map below.)
For Sydney, showers are likely for coastal suburbs and the northern beaches. "There's a particular bull's-eye of rainfall over there," Graeme Brittain, a meteorologist with Weatherzone, said.
"Thunderstorms are possible anywhere, really; it's difficult to pinpoint," Mr Brittain said, adding that afternoon and evening commuters in Sydney might be affected.
Jordan Notara, a forecaster at the bureau, said any thunderstorms over Sydney would most likely form separately from the wide sweep of storm activity now unfolding along the western edge of the ranges.
There are two distinct cloud bands within that range, with storms already moving across the Dubbo region earlier on Monday, he said.
NSW Severe storms; Dubbo, 48mm of rain in 2 hours with large hail. 7 degree temp fall??? Graham Creed (@WeathermanABC) March 13, 2017
Possible tornadoes
Mr Brittain said there was a chance that some of the super cells could spawn tornadoes.
"The indices and metrics that we use to forecast tornadoes are suggesting they are possible [in] the North West Slopes and Plains," Mr Brittain said.
The bureau's Mr Notara agreed that "there are chances of those phenomena" emerging during the day, but stressed that storms could still generate damaging wind gusts even without twisters forming.
(See Nick Moir's image below of a lightning strike near Dunedoo on Monday.)
For Sydney, the bureau was predicting the city would receive as much as 8 millimetres of rain for Monday, with Tuesday likely to be much wetter with 25-40 mm tipped according to updated bureau forecasts.
"Localised falls in excess of 50 mm are possible [on Tuesday], and they will be more in the form of rainfall than thunderstorms," Mr Brittain said.
Much of coastal NSW will get a soaking on Tuesday, according to the bureau. (See forecast chart below.)
The weather set-up creating such instability is an upper level pool of cool air exacerbating any precipitation, Mr Brittain said.
A high-pressure system over the Tasman Sea is directing an easterly flow over the coast, providing the necessary moisture for some areas to collect more than 100 mm of rain over the next few days, he said.
The upper-level cold air will dissipate after Tuesday but the easterly moisture flow will continue for much of the coming week, resulting in daily showers for Sydney for days to come including 10-20 mm on Wednesday.
Temperatures are also stuck in rut, with most days ranging from minimums of about 20 degrees to 26 degrees during the day, or slightly above the March average.
"For the next two weeks, there's no significant heat that will affect Sydney," Mr Brittain said.
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