Somerset 237 and 223 for 1 declared (Lammonby 101*, Abell 101*) lead Gloucestershire 76 (C. Overton 4-25) and 14 for 3 (Davey 2-7) by 224 runs
Tom Abell and Tom Lammonby hit unbeaten centuries as Somerset set Gloucestershire an unlikely victory target of 385 on the second day of the Bob Willis Trophy match at the Cooper Associates County Ground, Taunton.
A day totally dominated by the home side saw Gloucestershire bowled out for 76 from an overnight 13 for four, Craig Overton claiming 4 for 25 and Josh Davey 3 for 21.
That gave Somerset a first innings lead of 161. Skipper Abell and Lammonby then both finished 101 not out after an unbroken second-wicket stand of 211 had guided their side to 223 for one when Abell declared, aware of the forecast of rain on the final two days.
It was 20-year-old Lammonby's maiden first class century to follow his maiden first class wicket in Gloucestershire's first innings. The visitors were left with a tricky eight overs to negotiate, losing Ben Charlesworth, Chris Dent and Tom Lace before closing on 14 for three.
Gloucestershire were under pressure from the opening delivery of the day, having already lost four first innings wickets. Davey made the first breakthrough with the total on 29 when nightwatchman Matt Taylor was caught at point for 12.
The heat of battle between the two West country rivals was turned up when Jamie Overton thought he had George Hankins caught behind for six with the score 48 for five.
Umpire Paul Baldwin disagreed and Overton showed his displeasure, first by crouching with head in hands and then unleashing three successive bouncers at the Gloucestershire batsman.
The final ball of the over saw Hankins edge a low catch to Craig Overton at second slip and Somerset felt justice had been done.
Lace, who showed better technique than a number of team-mates, was bowled by Jack Brooks for 21, attempting to drive, with the scoreboard showing 56 for seven.
Gareth Roderick fell lbw to Craig Overton and Gordon Scott was caught behind off Lammonby's left-arm seam before Ryan Higgins was last man out for 15.
With a commanding lead, Somerset were able to approach their second innings positively. They suffered an early setback when Eddie Byrom chipped a catch to mid-wicket off a leg-side delivery from David Payne.
But from then on Lammonby and Abell took control, looking increasingly assured in a partnership that had added 81 by tea, which was taken at 93 for one. Suddenly, batting appeared straightforward on a pitch that had never looked to have any demons in it.
The final session saw Abell score more fluently to begin with, producing some textbook drives. Left-hander Lammonby, who had never scored even a half-century in first class cricket, moved cautiously to that landmark, having faced 122 balls and hit five fours.
Abell was first to his ton, with two to third man off Ben Charlesworth. It was his second hundred of the competition and was made off 153 balls, with 17 boundaries.
Lammonby was forced to hit out in a bid to reach three figures before the declaration and did so to great effect. Twice he cleared the ropes and a pulled four to fine leg off Scott took him to his century off 160 balls.
After one more delivery Abell called a halt and soon his seamers were cutting through Gloucestershire's batting as they had done in the first innings.
Davey had Charlesworth caught behind with a ball that lifted and bowled Lace with the first ball of the final over after Craig Overton had pinned Dent lbw. Only the weather would now appear to stand between Somerset and a third win from four Bob Willis Trophy games.