The MTA is preparing for a weekend nor’easter, with wind posing the biggest concern for the subway right now. But the agency says it is also getting ready for possible coastal flooding.

MTA chair and CEO Janno Lieber said strong wind could knock trees onto tracks in parts of the subway system that run outdoors. The MTA will watch conditions through the weekend and adjust service if needed. As of Friday’s news conference, it had no plans to stop subway service.

For riders who remember water pouring into stations during past storms, Lieber said that risk has not gone away. Water can come through street vents or back up when city sewers cannot handle a lot of rain in a short time. The MTA and the city are working on fixes at some vulnerable locations, he said, but that work is not finished.

The current forecast calls for rain spread over time, which reduces the risk of the kind of sudden downpour that overwhelms drains, Lieber said. He cautioned that the MTA will keep watching the forecast.

The agency has put storm doors in place at subway train yards in Howard Beach and Coney Island to help keep coastal floodwater out. Flooding at a yard can affect the MTA’s ability to get trains into service.

Buses are expected to keep running, though they may need to go around flooded streets. The MTA said Access-A-Ride service will also be available, but some trips could take a different route.

The storm could affect travel beyond the subway. The MTA is watching exposed rail lines, including Metro-North’s New Haven Line, and flood-prone spots on the Long Island Rail Road. It also plans to ban empty tractor-trailers and tandem trucks from MTA bridges and tunnels starting at midnight Friday because of the wind.

Before heading out, riders should check the MTA app, call 511 or sign up for service alerts on the MTA website.