Riding the Eye net momentum in May was Los Angeles affil KCBS, which leapfrogged KABC to become the month’s No. 2-rated late local newscast for the first time in 20 years.

According to Nielsen data for the sweep period that ended Wednesday, CBS 2 News at 11 p.m. with Laura Diaz, Paul Magers and recently added local weather vet Johnny Mountain averaged a 2.3 rating in adults 25-54 and 364,000 viewers overall — gains of more than 50% in both categories.

Numbers put KCBS ahead of KABC (2.1 rating in 25-54; 318,000), marking the first time since 1985 in a major sweep that didn’t include the Olympics that the Eye affil has risen to second. KNBC remained on top (3.2 rating in 25-54; 467,000 viewers), although it fell about 15% amid weakness at parent net NBC.

Gains for KCBS at 11 followed the station’s first primetime sweeps victory in adults 25-54 and total viewers since February 1998, when CBS aired the Winter Olympics. CBS programs on KCBS averaged a 3.5 rating in the 25-54 demo, edging KABC (3.4) and topping KNBC (2.9) for a second straight sweep.

KNBC’s third-place primetime finish makes its continued success at 11 all the more impressive.

KCBS also showed growth in prime access with “Entertainment Tonight” and “The Insider,” although it continues to lag its rivals there.