|Specsavers County Championship Division One, Headingley, day two|
|Yorkshire 145 & 57-3: Lyth 27*; Groenewald 2-20|
|Somerset 390: Trescothick 73, Gregory 73*, Rogers 63; Sidebottom 5-51|
|Yorkshire (3 pts) trail Somerset (7 pts) by 188 runs|
Lewis Gregory hit a career-best 73 not out as Somerset earned a 245-run first-innings lead over Yorkshire in their crucial encounter at Headingley.
Consistent batting by the visitors enabled them to reach 390 all out, despite Ryan Sidebottom taking 5-51.
Marcus Trescothick (73) and Chris Rogers (63) gave Somerset a good start and Gregory and Craig Overton (38) later put on 101 in just 20 overs.
Yorkshire were 57-3 at stumps, needing another 188 to avoid an innings defeat.
Should Somerset go on to win the game, the two sides would be separated by a single point in the Division One table.
But Middlesex would be clear favourites for the title should they win their current match against Lancashire at Old Trafford.
Sidebottom did his best to atone for Yorkshire's dismal opening-day batting effort, removing Rogers and James Hildreth in the same over at the start of play.
Liam Plunkett forced Trescothick to chop onto his own stumps, but Jim Allenby contributed 50 before falling lbw to Adil Rashid (3-99).
The partnership between Gregory, who hit 12 fours, and Overton boosted Somerset's lead before their last four wickets went down for 32 runs as they came up 10 runs short of maximum batting points.
Yorkshire's second innings again began badly as Gregory had Alex Lees caught at slip and Groenewald then bowled Gary Ballance and Andrew Gale to leave them deep in trouble.