Perth Scorchers booked their place in the final after edging a rain-affected game against the Sydney Sixers by five runs at the Sydney Cricket Ground.
They will host the final against the Hobart Hurricanes on Friday, with a new champion set to be crowned.
The Perth Scorchers went out to bat first and, led by Craig Simmons' century, scored 193-5 in their 20 overs.
His 112 was his second century of the tournament, and featured 11 sixes in 58 balls.
Perth were well-placed, but the game was plunged into uncertainty when torrential rain came down at the interval.
As the clock ticked down, the time available for play reduced. But just as the cut-off time approached for the game to begin, the weather relented enough to get the minimum of five overs in.
Chasing 54 in five overs to win, it was a slipshod performance from Sydney, who panicked their way to 48 for six.
Nic Maddinson stayed calm, scoring 36 from 16 balls, and had he enjoyed any meaningful support from his team-mates Sydney would surely have got it done.
But needing a boundary a ball for the last four deliveries he was run out on the penultimate delivery, and with it their hopes disappeared.
|Sydney Sixers vs. Perth Scorchers, BBL Semi-Final Scorecard|
|CJ Simmons||run out (Abbott/†Smith)||112||58|
|SM Katich*||c Lee b Hazlewood||26||21|
|SM Whiteman†||c Abbott b Lee||9||11|
|AC Voges||b Starc||31||24|
|MR Marsh||c †Smith b Starc||3||4|
|AJ Turner||not out||0||0|
|NM Coulter-Nile||not out||0||2|
|Extras||(b 1, lb 5, w 6)||12|
|Total||(5 wickets; 20 overs)||193||(9.65 runs per over)|
|MJ Lumb||c Cummins b Behrendorff||1||6|
|NJ Maddinson||run out (sub [HWR Cartwright])||36||16|
|RS Bopara||c Hogg b Behrendorff||0||1|
|SA Abbott||run out (†Whiteman)||1||3|
|MJ Cosgrove||c †Whiteman b Cummins||0||1|
|DLR Smith†||b Cummins||4||2|
|B Lee||not out||0||1|
|Extras||(b 4, lb 1, w 1)||6|
|Total||(6 wickets; 5 overs)||48||(9.60 runs per over)|
Any other result would have been cruel on Simmons especially, whose innings had thrilled the crowds.
He had made a gentle start, taking 14 deliveries to score five runs under pressure from Brett Lee and Josh Hazlewood.
But he clicked into gear, reaching his half-century in 37 balls, before adding another 58 runs in 21 deliveries.
As an example of clean-hitting, there are few innings to compare with it.
Simmons had support, with opening partner Simon Katich making a 21-ball 26, and Adam Voges striking 31 further down the order. But it was very much the Simmons show.
It would have been a tremendously difficult chase, but the heavens opened and changed the complexion of the game.
"I think we need a miracle here," said a rueful Katich, interviewed on television as the rain came down.
There was one, and Perth took full advantage.