The British number one beat Australian fourth seed Tomljanovic 6-2 7-6 (7) to move to within one match of a first tournament win in two years.
Konta’s serve was rarely threatened, and she secured victory over last year’s runner-up with a second match point in the second-set tie-break.
Konta knocked out in first round of Cincinnati Open; Norrie also beaten at pre-US Open tournament
Seventh seed Konta will now face Maria Sakkari in the final. The Greek, seeded sixth, who won 6-4 6-4 against Belgium’s Alison Van Uytvanck.
At the Prague Open, the Czech Republic’s Barbora Strycova missed out on a place in the final when she lost 6-3 6-0 to Jil Teichmann of Switzerland.
Karolina Muchova, also of the Czech Republic, will be her opponent following her 6-2 7-5 win over American Bernarda Pera.
In the qualifying stages for the Mutua Madrid Open, Australia’s Samantha Stosur lost 5-7 6-4 7-5 to Laura Siegemund of Germany.
Knee injury ends Konta’s Canadian Open
'The ultimate test' - Barty sets up Kerber showdown after sweeping Tomljanovic aside