Yorkshire 253 and 148 for 2 (Lyth 51, Ballance 50*) trail Somerset 437 (Compton 156, Abell 75, Trescothick 66, Patterson 4-54, Rashid 4-116) by 36 runs
Yorkshire opener Adam Lyth celebrated his 27th birthday with yet another fine batting display on the third day of the new title-holders match against Somerset at Headingley.
Lyth, Division One's leading run-scorer, signed off the season with a cleanly-struck 51 to give him 1,489 runs at an average of 67.68 - but he left Yorkshire with some work still to do in their bid to save the match.
They will resume on the final day on 148 for 2, 36 runs behind, and will be anxious to preserve their unbeaten home record before the club re-present the Championship Trophy in front of the home supporters.
Lyth ended his splendid season as he began it - with half-centuries against Somerset. In between, he plundered two double-centuries, four centuries and a further four half-centuries.
"I got a few hugs on the field this morning from team-mates who had still to wish me happy birthday," he said. "It felt good to end the season with another half-century but it would have been an even better birthday present if I could have got an extra 11 runs to finish up with 1,500.''
Lyth, who has been included in the squad for England's Performance Programme visit to Sri Lanka, added: "I am very happy with how it has gone for me this season and hopefully the winter will turn out to be just as good if not even better.
"It feels great to have scored runs and taken catches this summer but being part of the Championship-winning team means even more to me.''
"It would be nice now if we can bat for a long time tomorrow and if we do well enough we may be able to leave Somerset with a difficult 25 or 30 overs to face themselves.''
After Somerset had progressed their overnight 319 for 3 to 437 all out to give them a first innings lead of 184, Lyth opened up Yorkshire's reply with Alex Lees - who has also enjoyed a magnificent summer in which he, too, has ear-marked himself as a future England player.
Lees reached 23 shortly before he pushed defensively at Peter Trego and feathered a catch to wicket-keeper, Craig Kieswetter, to leave Yorkshire on 44 for 1 in 12 overs.
That left the hosts still needing a solid base to their innings in order to feel more secure and Gary Ballance began soundly enough but he had an escape on 24 when he mis-timed a pull at left-arm spinner, Jack Leach, and Jamie Overton spilled an easy catch running towards square leg.
Shortly after tea, Lyth off drove Leach for his eighth boundary to reach his 50 and then mis-timed his pull at Trego to hole out to Tim Groenewald at mid-on.
Ballance, partnered by Joe Root, sealed his own successful summer for both county and country, by making his 50 from 102 balls with four boundaries but the light quickly closed in and the players came off with 17.4 overs of the day's ration still remaining.
In the morning, 20-year-old Somerset rookie, Tom Abell, added only four to his overnight 71 before Jack Brooks found enough movement to have him caught at second slip by Lyth and when nightwatchman Leach was dismissed by the industrious Steven Patterson for a cleanly hit 43, Somerset were 364 for 5.
Trego dashed his way to 41 from 30 balls with four fours and two sixes but the second half of the batting swiftly crumbled to Adil Rashid who grabbed four wickets in 14 balls while conceding only five runs.
The legspinner ended with 4 for 116 but much of the hard work was done by Patterson who deservedly returned his season's best figures of 4 for 54.