Bundle up and prepare for delays: with the potent omicron variant cutting into the on-duty workforce and frigid cold forecast for Tuesday, the MBTA continues to face obstacles running service on a normal schedule.

About 50 T employees are out sick with active COVID-19 cases, MBTA General Manager Steve Poftak said Monday, an uptick that has pressed the nearly 6,000-employee agency back into nearly the same distressed position that last month prompted officials to cut service on many bus routes.

In early December, the T was dropping about one in every 20 scheduled bus trips because of a driver shortage. The new winter schedule that took effect Dec. 19 shaved bus frequency by about 3 percent to mirror the limited workforce, but the benefits did not last long.

"What we saw right after we made that reduction was that dropped trips dropped, which is what we expected to see, and then omicron almost immediately swooped in and took hold," Poftak said in an interview. "We are (now) seeing dropped trip numbers that I would say are roughly equivalent to what we saw before we reduced service."

The workforce impact so far has not been as dire as last year. During the previous winter surge, Poftak said, the MBTA peaked at 114 active employee cases. Agency leaders have long said they expect for every positive case, two other employees are out of work and unavailable while quarantining or caring for a loved one impacted by COVID.

Still, Poftak said he believes more staffers have called in sick due to COVID-19 than the about 50 who indicated they tested positive. Like leaders of many other agencies and businesses, Poftak said the ongoing surge fueled by omicron has "definitely impacted our employee availability."

Commuter rail operator Keolis has been feeling the strain, too. Poftak estimated the company has "roughly the same number of active cases as we do, and they're about a third of our size."

Starting Monday, the T and Keolis eliminated 26 of the roughly 500 daily trips across the network to manage the staff impacts. Most of the temporary cuts were local service to Reading on the Haverhill Line and to Framingham on the Worcester Line, according to Poftak.

Officials have not made any additional changes to the bus or subway schedule.

The MBTA is not alone in struggling to attract and retain enough workers. Business groups in virtually every field have complained of shortages in recent months, and last-minute closures have become common.

Poftak said the T wants to expand its active bus operator workforce by about 180 positions. A class of 27 new drivers started last week and a second class will start this month, which Poftak called a "pretty unprecedented" pace.

In December, the T approved a contract with Boston Carmen's Union Local 589 that allows the agency to offer an unspecified one-time hiring bonus to attract new employees. Poftak said Monday that officials are still finalizing those plans and would share more in the "coming weeks."

On top of the depleted workforce, the tundra-like conditions expected to hit Massachusetts between Monday night and Wednesday morning — with minus-zero wind chills in the forecast — could create issues for the MBTA's vehicles and slow down travel times.

The T on Monday cautioned commuters about the outlook, urging riders that delays are possible even as the agency makes "every effort to operate subway trains and buses at or near regular weekday schedules."

Of particular concern, Poftak said, is that the cold snap will follow a relatively mild weekend because too quick a change in temperature could create problems, especially for railways.

"Vehicles can be impacted by the cold weather," he said. "At some point, it hit 45 degrees yesterday. Some time tomorrow, it's going to be, I think, five degrees or less. That obviously puts a lot of stress particularly on rail."

MBTA crews will store many train cars and buses indoors overnight to prevent exposing them to the harsh elements, and they will perform regular check-ups on vehicles that stay outdoors. Trains will cycle in and out of yards to avoid long stretches of idleness in the cold, workers will test brakes and propulsion systems for any moisture or ice buildup, and crews will perform inspections to ensure switch and third rail heaters are functioning.

The winter has stunted a months-long trend of MBTA ridership increasing, albeit still below pre-pandemic levels. Poftak said he wants to see a few more weeks of data before determining if the recent slowdown should be attributed to the omicron surge or to a typical holiday slowdown.

Back in the spring, employee COVID-19 cases at the MBTA dropped below 20. Poftak said it's not yet clear if the ongoing wave will continue to rise or if omicron's blow to the workforce has already peaked.

"If we've learned anything in the last two years, it's every time you think you've out-thought this virus or have a rock-solid scenario for the next year, you end up going back to the drawing board," he said.

Poftak said he does not think the MBTA needs additional support from the Baker administration or the Legislature to navigate the dire straits.

"We have the resources, particularly in terms of operating funds given the amount that we've gotten from the federal government," Poftak said, referring to the roughly $1.9 billion in emergency aid the T received from Washington, D.C. "The faster we can invest in our infrastructure, the better off we'll be in terms of reacting to some of this particularly cold weather stuff. But we've invested at an unprecedented level over the last two years. We need to keep that up."

"So no, there's not a real ask on my part here," Poftak added.