The Parkes Spacemen have been left devastated after four crushing losses against rivals Forbes in a cold and wild derby clash at Jock Colley Oval.

Parkes' firsts, reserves, league tag and Under 18s all managed to cross the line once in each of their matches on Sunday but that's where the story ends.

In quite the uniform effort, Forbes held Parkes back from scoring any more tries in all grades.

It was a big blow to the club that had very high hopes leading into the derby - the final scores were 6-50 in first grade, 4-26 reserve grade, league tag 6-14 and Under 18s 6-46.

Parkes first grade captain coach Sam Dwyer said they are disappointed with the weekend but isn't letting it bring them undone.

"We are pretty disappointed with the result but that's the way it goes sometimes," he said.

"You've got to take the good with the bad."

After more than 20 minutes of back-and-forth play in firsts in freezing rain and even light hail, Forbes broke the deadlock scoring three tries before the break and taking a commanding 0-14 lead into halftime.

From there, the Magpies never looked back.

"We knew that Parkes were going to come out hard ... and they did that," Forbes captain Nick Greenhalgh said.

"They charged through the middle there and it was back and forth for a long time but we knew if we stuck to our structure and stuck to our defence, once we got on top we'd stay on top, and that was the case."

A second-half blitz saw Forbes extend their lead to 0-38 before Parkes finally got on the scoreboard with a converted try in the final 15 minutes.

But Forbes responded immediately, tightening their grip on the game in the closing stages.

The Magpies now sit on top of the Peter McDonald Premiership ladder, level on points with Mudgee Dragons but ahead on for-and-against.

The Spacemen are at home again this weekend, hosting the Lithgow Workies.

FIRST GRADE: FORBES MAGPIES 50 Chad Porter (3), Jack Smith (2), Nick Greenhalgh, Farren Lamb, Jordan Hartwig Conversions Nick Greenhalgh: 7 conversions PARKES SPACEMEN 6.