Yorkshire 361 ((Hill 90, Wharton 63, Bess 50, Govin 4-67) and 116 for 1 (Lyth 55, Bean 53*) lead Glamorgan 239 (Ingram 82, Coad 4-55, Fisher 4-55) by 238 runs
Yorkshire took a significant step towards a return to Division One by taking control of this game, despite a late fightback from Glamorgan's tail in saving the follow-on.
Matthew Fisher and Ben Coad took four wickets apiece to dismiss the Welsh County for 239, a first-innings lead of 122. Glamorgan's highlight was Colin Ingram's 82 making him the highest run-scorer in County Championship cricket so far this season.
Adam Lyth and Finlay Bean had a century opening partnership to extend Yorkshire's lead to 238 with two days of the contest remaining, both notching half-centuries to close on 116-1, Lyth lbw to James Harris just before the close.
A victory would put second-placed Yorkshire in a strong position to return to Division One after a two-year gap, with leaders Sussex facing third-placed Middlesex in the final round of matches.
Yorkshire's opening bowlers, Coad and Fisher, exploited the overcast conditions that faced Glamorgan's batters before lunch.
In that time those two bowlers were able to swing the match firmly the way of the visitors picking up six wickets with two spells each.
Glamorgan skipper Sam Northeast is a good man to get early as he is capable of getting big scores once in, Coad delivering with one which came back and pinned the opener lbw.
Kiran Carlson nicking off first ball, and Ben Kellaway going in similar fashion for 4, were both undone by classy away swing bowling, Fisher getting Carlson caught George Hill in the slips and Coad claiming the wicket of Kellaway caught behind by Jonny Bairstow.
However Asa Tribe and Chris Cooke both contributed substantially to their own downfalls throwing the bat at wide swinging deliveries, Tribe caught Lyth at second slip and Cooke pouched by Bairstow.
Fisher claimed his fourth wicket with what turned out to be the final ball of the first session, pinning Tim van der Gugten lbw.
All the time Ingram was watching on from the other end, finding none of the demons which troubled his partners.
Off-spinner Dom Bess had to wait for a chance to bowl, but when it came he grabbed the all important wicket of the South African, clean bowled looking to cut a ball which was not quite there for the shot.
Mason Crane's 29, in a partnership of 63 with Ingram, still left Glamorgan 40 short of the follow-on target, however James Harris and Andy Gorvin saw them past that mark with surprising ease, in a partnership of 67.
The return of Coad ended the innings, trapping Harris lbw for a well made 40 and then clean bowling debutant Ben Morris to earn a lead of 122 on the first innings and a total of six bonus points. Glamorgan were all out for 239, having been 37 for 4 and 98 for 6.
Yorkshire's opening pair of Lyth and Bean were generally untroubled as they extended the lead to comfortable territory, before Lyth was dismissed just before the close as they look for a declaration some time tomorrow.
