Various forecast services are predicting a good chance of 10-50mm as the rain system moves through the district from the north-east of the state.

It would be welcome after the balance of NSW slipped over into drought, but BOM forecaster Anita Pyne said the bureau’s computer modelling was “a bit uncertain at the moment”.

Ms Pyne said the rainfall would be brought on from Friday by a collision between moisture carried inland by coastal winds, and a trough coming across central NSW.

“We’re looking at a high chance of showers about the northern coastal parts … becoming more of a moderate to slight chance further west; the North West Slopes and Plains and the Central West kind of districts,” she said.

“The further west and south you go, the more chancy it becomes.”

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Ms Pyne said some of the bureau’s models were “going hard, and some models not so much” on the chances and amount of rain.

However, different services’ overall predictions were more or less in agreement.

At Narrabri on Saturday, for example, Weatherzone gave an 80 per cent chance of rain, with a possible 10-20mm falling; while BOM put the possible falls at 15-25mm.

According to their rain forecast definitions, the percentage is the chance of any more than 0.2mm falling; there is then a 50 per cent chance of the falls reaching the lower figure, sliding to 25 per cent of achieving the higher rainfall figure.

In a statement earlier in the day, Weatherzone forecasters said it looked like “the slow-moving nature of this system brings the best chance of rain so far this year for large areas of northeast NSW”.

The two services also found consensus on their predictions of the patchy nature of the falls.

“Some drought affected areas of New South Wales are a good chance of seeing soaking rain this weekend, but unfortunately some will miss out,” Weatherzone said.

It predicted thunderstorms at the weekend; so did the bureau.

“There’s also probably going to be some thunderstorms associated with this system; thunderstorms can dump huge amounts of rain in one little spot, and 5km down the road they might see barely anything, so it could be quite patchy at this stage,” Ms Pyne said.

As for the rain’s impact on the drought conditions, the best that could be said was that something was better than nothing.

“The soil moisture levels have been so low for so long it’s probably going to take more than just one rainfall event to bring any lasting relief from the drought situation.”