Heat skipper Jess Jonassen sent the Thunder in at Allan Border Field and marshalled her bowlers to perfection as the visitors crashed to 7-69.
A record WBBL stand of 64 for the eighth wicket by Hannah Darlington (40no) and Taneale Peschel (24no) lifted the Thunder to 7-133.
But the Heat polished off the runs in 15.2 overs for a nine-wicket win to set up a WBBL final showdown away against Melbourne Renegades at the MCG on Sunday.
India international Jemimah Rodrigues was dropped three times, two of them sitters, on her way to a skilled 43 off 30 deliveries before retiring hurt. She combined with opener Georgia Redmayne (50no) to set up the run chase.
Georgia Redmayne's unbeaten 50 against the Thunder has helped Brisbane into the WBBL final. (Russell Freeman/AAP PHOTOS)
Rodrigues had injured her left wrist in the field and had to retire in the 10th over. She is likely in doubt for the final but Redmayne and Charli Knott (19no) at least showcased the Heat's depth.
Parsons, 21, earlier took 3-10 in three classy overs to set up her side's sixth straight win.
She received her second official player of the match award after earlier taking 3-22 against Renegades.
"It is pretty nice to do it in front of our special supporters," she said.
"This is my debut season. I started alright and went down a little bit in the middle but I have slowed things down and had more belief in myself.
"Cam Boyce our leg spin coach has been awesome instilling belief. Last year it was disappointing to miss out but it gave me 12 months to hone my skills.
"To be able to have the opportunity to play a final on the MCG is a dream come true. I don't think it gets much better."
Thunder opener Georgia Voll (20) was looking good against her former side before chopping on to the first ball of Nicola Hancock's spell.
Jonassen showed immediately why she was named in the WBBL team of the decade when she cleaned up Chamari Athapaththu with her first delivery, a beauty that drifted in and spun away.
Wicketkeeper Tahlia Wilson holed out to Parsons and the visitors stumbled to 3-51.
Jemimah Rodrigues blasted 43 off 30 balls before retiring hurt, and is in doubt for the final. (Russell Freeman/AAP PHOTOS)
Parsons snared the key wicket of skipper Phoebe Litchfield (15), who was brilliantly caught by Jonassen at mid-off as she leapt high and snaffled a well hit drive above her head.
And Parsons had two in the over when Georgia Adams skied one.
Jonassen snared former Heat allrounder Sammy-Jo Johnson, and at 7-69 the Thunder were in dire straits before Darlington and Peschel lifted them to a competitive total.Â
Both posted their career-best scores and unleashed an array of sixes and fours as the Heat bowlers dished up rubbish in the latter overs.
The stand broke the previous record of 60, also unbeaten, set by Lauren Ebsary and Piepa Cleary in 2018 for Perth Scorchers against Melbourne Renegades.
The Heat lost Grace Harris (7), stumped early after a wild heave, to give Sam Bates her 20th wicket of the season. Redmayne and Rodrigues then ensured the hosts were able to cruise to victory.
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