NSW is on alert with flash flooding expected across the state, more than a month's worth of rain is likely to cause flooding along central parts of the NSW coast during the middle of this week.
Transient low pressure systems are difficult to predict ahead of time, much like their more intense and longer-lasting cousins, east coast lows.
An Initial Flood Watch was issued on yesterday afternoon for coastal rivers between the Central Coast and Illawarra, where minor to moderate river flooding is possible from tomorrow.