Chris Wright took five for 24 and Keith Barker five for 36 as only Brett D'Oliveira, Chris Russell and Phil Hughes reached double figures for the hosts at New Road.
The Bears responded by reaching 215 for two, with Varun Chopra 115 not out and opening partner Ian Westwood (54) also almost emulating Worcestershire's team total.
And second-placed Sussex managed only one batting point against Somerset, meaning a win with a first-innings total of 350 or more will guarantee Warwickshire the title with a game to spare.
Alfonso Thomas and Abdur Rehman took three wickets apiece and Marcus Trescothick pouched five slip catches as Sussex were dismissed for 221 after being put in, despite 65 from Ed Joyce.
Somerset closed at 30 for one from 12 overs, Arul Suppiah the man out for one.
Middlesex reached 389 for six against Lancashire to leave the Red Rose deep in relegation trouble. Neil Dexter was unbeaten on 123, having put on 148 with Gareth Berg (83) and an unbroken 77 with Steven Crook, who raced to 45no from 52 balls.
Surrey, the only team seemingly still within range of the bottom two, were struggling to reach a second batting point as they ended the first day on 242 for nine against third-placed Nottinghamshire.
Zander de Bruyn made 71 and Gary Wilson 68 but Ben Phillips and Harry Gurney took three wickets apiece to check the hosts' progress. Tail-enders Stuart Meaker and Tim Linley will be tasked with adding eight more runs to their stand of 11 to lift the Brown Caps a point further clear at the foot of the table.
They began the day 17 ahead of Lancashire, with Worcestershire a point further back.
Derbyshire boosted their County Championship Division Two title hopes by bowling out third-placed Kent for 261 on day one at Canterbury.
Geraint Jones made 80 but received little support before falling to Tim Groenewald, who led the visitors' attack with three for 63.
Victory would leave Derbyshire - who led the division by 19 points at the start of play and were 32 for one at stumps - all but uncatchable at the summit.
Second-placed Yorkshire enjoyed a similarly successful day in the field, dismissing Glamorgan for 272 at Headingley.
Steven Patterson led the way with four for 49 as the visitors folded following an opening stand of 124 between Will Bragg (92) and Nick James (38). Stewart Walters contributed 42.
Yorkshire were 20 without loss in reply when stumps were drawn.
Fourth-placed Hampshire remain firmly in the hunt for promotion and kept up their challenge by ripping out Essex for 180.
David Balcombe took four for 57 and Sean Ervine's 11 overs yielded two for 19 as only Mark Pettini (58) offered any serious resistance for the visitors.
Michael Carberry made 42 and Bilal Shafayat was unbeaten on the same score as Hampshire reached 165 for four, just 15 behind.
Gloucestershire were bowled out for 220 against Northamptonshire as Luke Evans took four for 38 - but bounced back by reducing the visitors to 73 for seven.
