Yet, the seasoned Weissenbach made an impressive push over the last mile and a half, taking control over the final loop while launching into her final kick near the end.
Weissenbach caught up with Vargas with half a mile left and built a comfortable lead over the final 100 meters up the course's grassy knoll.
"Today, this wasn't about individual efforts. This was a league meet and about the team," Weissenbach said. "It was a good time for our team to work on finishing and we all finished strong."
Weissenbach led the way by earning a win in 18:15 and paced the Wolverines, ranked No. 2 in Division IV of the CIF Southern Section, to a team victory over Sherman Oaks Notre Dame, 37-41.
Despite her sizable lead at the two-mile marker, Vargas said she was always aware of Weissenbach.
"I kind of figured that she was going to make her charge. She's a great runner and I tried to build as big of a lead as I could," Vargas said.
"Overall, the team was hoping to finish second today and that didn't happen. We'll try to move up at the next league race."
The Tologs took third with 61 points ahead Louisville (113), Chaminade (134) and Alemany (192).
Flintridge Sacred Heart's third-place team consisted of Maddie Peterson (ninth, 19:39), Nora Nelson (14th, 20:06), Riley Gilmartin (15th, 20:12) Annie Maguire (21st, 20:36), Olivia Mendoza (24th, 21:00) and Casey Basso (27th, 21:23).
On the boys' side, there was little doubt that the Loyola Cubs, ranked No. 2 in Division II of the CIF Southern Section, were the unquestioned favorite.
While the race proved tighter than expected, a Cubs roster with a couple of Pasadena runners triumphed, 44-76, over Crespi.
"We enjoy coming out here and being the favorite," said Loyola senior Ned Trimm, a Pasadena resident. "It's nice to know that everyone is looking to beat you."
Trim took fifth overall with a time of 15:37 and was the Cubs' lead runner. Loyola's Ross Wiggins, an Altadena resident, was the Cubs' No. 7 runner, but finished well by taking 16th place (16:35).
Locally, St. Francis took sixth in the day's competition with 119 points.
Golden Knights' senior Colin Peterson led the way, earning 10th (15:53).
The St. Francis squad included senior Andrew Evans (22nd, 16:52), sophomore Robbie Palmer (26th, 17:01), sophomore Max Sinclair (29th, 17:05), junior J.D. Kiefer (32nd, 17:13), sophomore Nick Sanchez (38th, 17:48) and senior Lance Bird (39th, 17:49).
Harvard-Westlake's Aaron de Toledo was the race victor, winning in 15:20.