A stand of 164 between Adam Lyth and Kane Williamson put Yorkshire in firm control of their County Championship clash with Sussex at Hove.
Lyth made 93 and Williamson an unbeaten 80 as Yorkshire reached 246-4, trailing by 46, when bad light stopped play with two overs remaining.
It was another difficult day for Sussex which was only brightened by the bowling of Steve Magoffin and a maiden Championship wicket for Ashar Zaidi.
Magoffin bowled superbly for his 1-29 from 25 overs while Zaidi removed Lyth as he took 1-41 from 17 overs.
James Anyon also took two late wickets to spoil Yorkshire day slightly but proved expensive (2-88) and with Lewis Hatchett posing little threat Sussex badly missed Chris Jordan.
Magoffin was exemplary once again and deserved more than his solitary scakp of Phil Jaques who he trapped lbw in his fourth over for 21.
Magoffin received little support from fellow seamers Anyon and Hatchett, however, to allow Lyth and Williamson to get settled in the crease.
Lyth was first to reach his half century off 114 balls after lunch while Williamson followed from one delivery fewer.
The pair put on 164 for the second wicket before Lyth fell seven short of his century when he edged Zaidi to Matt Prior at slip.
Anyon finally got some reward for his efforts when he had Andrew Gale caught behind from the final over of the old ball and then bowled Jonny Bairstow with the new ball for eight.
Stephen Patterson came in as nightwatchman and survived a tough examination from Magoffin as he and Williamson safely made it through the 5.30pm when the umpires took them off in fading light.
Earlier, Sussex had added 16 to their overnight total of 276-9 before Ryan Sidebottom picked up his fourth wicket by having Lewis Hatchett caught in the slips for 21, leaving Ben Brown unbeaten on 84.
Comments: Our rules
We want our comments to be a lively and valuable part of our community - a place where readers can debate and engage with the most important local issues. The ability to comment on our stories is a privilege, not a right, however, and that privilege may be withdrawn if it is abused or misused.
Please report any comments that break our rules.
Read the rules here