Both sides will be keen to get the upper hand before the tie returns to Northern Ireland next week, with the winner set to face Bodo/Glimt in the second qualifying round.
Match preview
Last year, RFS won the Latvian Higher League title by just one point to seal their spot in Champions League qualifying.
RFS are currently on course to retain their crown, having picked up 56 points from 22 matches to establish a seven-point lead over second-placed Riga.
Viktors Morozs's side will carry significant momentum into Wednesday's fixture after winning 10 of their previous 11 matches, including a thumping 7-0 victory in their most recent outing against FS Jelgava.
They have only made one previous appearance in Champions League qualifying, losing on penalties to HJK Helsinki in the first round in 2022-23.
That same season they went on to compete in the Europa Conference League group stage, but they were unable to replicate that feat last term, falling in the second round of qualifying in UEFA's third-tier competition.
Larne are set to make a second consecutive appearance in Champions League qualifying after retaining their NIFL Premiership title last season.
They won 27, drew nine and lost just two of their 38 league matches to finish five points clear of Linfield in second position.
As a result of their league success, Larne were involved in the NIFL Charity Shield on Friday, with Lee Bonis and Andy Ryan getting on the scoresheet to clinch the silverware with a 2-1 win over Glentoran.
They will now turn their focus to their first Champions League outing since suffering an extra-time defeat in last season's first-round qualifying tie against HJK.
That result has contributed to a poor run of form which has seen Larne fail to progress from any of their last four European ties since getting the better of AGF Aarhus in the second round of Europa Conference League qualifying in 2021-22.
Rigas Futbola Skola form (all competitions):
W
W
L
L
Larne form (all competitions):
W
L
W
W
D
W
Team News
Goalkeeper Fabrice Ondoa is poised to retain his place after making his RFS debut in the recent 7-0 win over Jelgava.
Having scored six goals in the last seven matches, forward Ismael Diomande will be looking to continue his fine run of form when he leads the line against Larne.
As for the visitors, Tiernan Lynch is likely to line up with three centre-backs, which could see Baris Altintop, Cian Bolger and Aaron Donnelly all given starting spots.
Bonis and Ryan scored 57 competitive goals between them last season, and the pair will resume their potent forward partnership for Wednesday's away fixture.
Rigas Futbola Skola possible starting lineup:
Ondoa; Savalnieks, Prenga, Lipuscek, Mares; Panics, Kigurs; Ikaunieks, Kouadio, Deocleciano; Diomande
Larne possible starting lineup:
Ferguson; Altintop, Bolger, Donnelly; Cosgrove, Thomason, Randall, McKendry, Ives; Bonis, Ryan