The U14.2 and U16.2 teams have advanced to the grand final with wins on Tuesday night at Kiama Sporting Complex.
The 14.2 team overcame Kiama 2-1 in extra time and will meet Albion Park in the grand final at 12.30pm Saturday at Unanderra Oval.
The 16-2 team won 4-1 against Port Kembla and will play Balgownie in the grand final at 8pm Friday.
They join the 12.3, U16.1 and U17.1 teams in qualifying for this weekend's junior grand finals, being played at Unanderra Oval.
The 16.1 team also play at 8pm Friday against Unanderra following their win in the preliminary final last Sunday after Henry Jenkins scored off a Cooper Grossman corner in extra time to secure a 2-1 win over South Coast United
The U12.3 team, pictured below, secured their grand final berth last Saturday after goalkeeper Tane Mathews-O'Brien saved all four Balgownie attempts during a penalty shoot-out, which was needed to break a 0-0 deadlock at the end of regular and extra time.
They now face Helensburgh in the grand final at 9.45am Saturday at Unanderra Oval.
The U17.1 team had already qualified for their grand final at Unanderra Oval on Sunday at 8.30am after winning the major semi-final the weekend before and will play the winner of Wednesday night's Balgownie-Coledale match.
The full junior grand final draw is below:
Meanwhile, the Thunder Youth Grade and Reserve Grade will play semi-finals on Saturday but First Grade's season is over after a 1-0 extra time loss to Balgownie on Tuesday night.
The Thunder Youth Grade team play Wests in the minor semi-final at Wetherall Park, Primbee, while Reserve Grade meet Fernhill at Tarrawanna Oval for a place in the grand final at WIN Stadium on September 24.
The Community League finals series will now be played over two weekends after Saturday's semi-finals were cancelled, with the Thunder Division 2 team to play third placed Jamberoo Rovers at Judy Masters Oval, Balgownie at 12.15pm Saturday.
In Division 3, second-placed Gibson Park Rangers play Albion Park City and fourth-placed Thunder White take on league champions South Coast United Blue in a double-header at Ian McLennan Park from 12.15pm Saturday.
Thunder Blue play second-placed Razorbacks in their Division 4 semi-final at Beaton Park at 12.15pm Saturday.
WEEKEND finals matches INVOLVING Thirroul teams
Friday, 9 September
U16.1 v Unanderra - 8pm at Unanderra Oval (grand final)
U16.2 v Balgownie - 8pm at Unanderra Oval (grand final)
Saturday, 10 September
U12.3 v Helensburgh - 9.45am at Unanderra Oval (grand final)
U14.2 v Albion Park - 12.30pm at Unanderra Oval (grand final)
Youth Grade v Wests - 10am at Wetherall Park (minor semi-final)
Reserve Grade v Fernhill at Tarrawanna Oval - 12.15pm TBA (major semi-final)
Thunder Div 2 v Jamberoo Rovers - 12.15pm at Judy Masters Oval
Gibson Park Rangers (D3) v Albion Park City - 12.15pm at Ian McLennan Field
Thunder White (D3) v South Coast United Blue - 2.30pm at Ian McLennan Field
Thunder Blue (D4) v Razorbacks - 12.15pm at Beaton Park
Sunday, 11 September
U17.1 v Coledale - 8.30am at Unanderra Oval (grand final)