Firth is the leading light among nine Yorkshire players placed inside the top 64 after day one, which also included action at Ganton.
The 287-strong field play one round at each course, with the top 64 and ties progressing to the match play stage, which will be held at Ganton.
Firth had six birdies and just one bogey in his 67, while Fulford’s James Cass sits eighth after a 70 that also included six birdies, but four dropped shots.
Tied 18th is Cass’s club-mate Craig Smith, on 71 after a handful of birdies.
Other Yorkshire competitors inside the cut-off mark at halfway – and who all played at South Cliff – are Wath’s Nick Poppleton and Middlesbrough’s Angus Montgomery, both with 72; Driffield’s Ryan Gray, Wakefield’s Scott MacGregor, Cookridge Hall’s Tom Murray, and Wheatley’s Ben Brewster, all 73.
The leading score at Ganton was 71, meaning the likes of Howley Hall’s Ben Hutchinson, on 74, Malton & Norton’s David Hague and Hallamshire’s Alex Fitzpatrick, both 75, and Cookridge Hall’s Tom Broxup and Hull’s Steve Robins, on 76, look handily placed to challenge for a match play spot.
Strong winds were in evidence at both courses and the first 31 players on the leaderboard – who were all under par – all played at Scarborough South Cliff.
At Ganton – acknowledged to be the tougher of the two championship courses – the combination of strengthening winds and thick rough pushed up scores and the par of 71 was equalled by only two players, Laird Shepherd (Rye) and Will Enefer (Wrekin).
South Cliff, with its combination of parkland and clifftop holes, may be the more forgiving of the two courses, but was certainly no push over.
“It was very windy out there, but I didn’t get into any trouble,” said Firth, who says that the wind helps him to concentrate.
“I don’t mind where I finish, I just want to qualify and I know Ganton is going to be hard.”
His score, returned at the end of the day, was one better than that of Gian-Marco Petrozzi (Trentham).