Mark Suppelsa, Tom Skilling and Lourdes Duarte

The busiest television newsroom in Chicago is about to get busier.

WGN-Channel 9, which leads the market in producing 54 hours of local news each week, plans to add another hour of news — from 4 to 5 p.m. Monday through Friday — starting in September.

Greg Easterly, president and general manager of the Tribune Broadcasting station, told staffers Wednesday the expansion would reinforce the brand of “Chicago’s Very Own.” “We have plenty of decisions and brainstorming in front of us . . . but I thought you all would like to know where we are headed,” he wrote in a memo. “It’s clear WGN has a unique place in the market and a true connection to Chicago — let’s build on it.”

No decision has been made on a talent lineup for the new 4 p.m. newscast, but insiders said it’s likely that news anchors Mark Suppelsa and Lourdes Duarte and chief meteorologist Tom Skilling, who currently front WGN’s 5 p.m. news hour, will be involved. There also may be a role for Micah Materre, who co-anchors at 9 p.m. with Suppelsa.

At 4 p.m., WGN would compete with ABC-owned WLS-Channel 7, which starts its afternoon news at that hour. NBC-owned WMAQ-Channel 5 starts at 4:30 p.m., and CBS-owned WBBM-Channel 2 starts at 5 p.m. Fox-owned WFLD-Channel 32 does not air afternoon news.

The expansion comes as WGN faces the loss of two syndicated programs from its daytime schedule this fall. “The Rachael Ray Show,” which airs at 10 a.m., is moving to ABC 7, and “The Test,” which airs at 3 p.m., has been canceled. New to WGN’s lineup is the syndicated “Celebrity Name Game,” for which no time slot has been announced.

Easterly also has said he is exploring “locally produced options,” including a possible daytime talk show, to fill one of the available hours on the weekday lineup.