This week has been dry and sunny, with the bulk of New South Wales basking in unseasonable warmth, but it is all about to change. During Friday, a strong cold front will drop temperatures markedly. Ahead of the front, a warm northwesterly wind will push the mercury up to a pleasant mid-twenties over much of northern and central NSW, including Bourke and Sydney. Then that front will shave five-to-ten degrees off temperatures in about a day. Aside from the cold burst, modest rainfall totals will accompany the change. We will see falls of 10-to-25 millimetres across much of the south and generally five-to-15mm in the north. For the Riverina, this rainfall event is likely to push the August rainfall totals into the above-average range. In the Upper and Lower Western districts, this rain will further increase the monthly surplus. From Sunday a ridge of high pressure will build behind the system. This will bring the return to dry and mostly sunny conditions through the day, but a repeat of chilly and frosty mornings. These settled conditions will be short lived, with indications of a much more intense rain-bearing system reaching the state by about mid-week.