Warwickshire made it through to the Clydesdale Bank 40 final for the second time in three years with a 23-run triumph over Lancashire.
The 2010 winners became the first visiting team to triumph at Old Trafford in the tournament this summer thanks mainly to a century from Varun Chopra.
The former Essex opener, one of several candidates to replace Andrew Strauss in England's Test side, made 110 from 124 deliveries, anchoring the Bears' total of 250-6 after they had won the toss and opted to bat first.
Lancashire crumbled to 90-5 in response and although Paul Horton did his best with a brave knock of 78, they were eventually bowled out for 227.
Neil Carter claimed 4-38 to condemn Lancashire to an 11th defeat in their last 12 semi-final appearances in all forms of limited-overs cricket.
Horton was one of the left-arm seamer's victims having almost single-handedly kept the Lightning alive, hitting seven boundaries in his 63-ball knock before holing out to mid-off in the 39th over.
Carter had dismissed opening duo Stephen Moore and Tom Smith in his opening spell before Steven Croft dragged Chris Wright (3-48) onto his stumps to leave Lancashire in trouble at 50-3.
When South African Ashwell Prince top-edged a swipe to mid-off, Lancashire had lost half their side before reaching three figures. Horton put on 37 in four overs with Glen Chapple, but it was all a case of too little, too late.
Warwickshire, in contrast, had been given the perfect platform by an opening stand of 126 between Chopra and Will Porterfield, who scored 67 from 65 balls.
Their success, which sets up a showdown with Hampshire at Lord's on September 15, was achieved despite the absence of Tim Ambrose, who suffered a thigh injury after the toss and was replaced by Richard Johnson.