The MBTA issued a warning to commuters today that sub-zero temperatures tonight and tomorrow will likely wreak more havoc on the already beleaguered subway lines. And, as the region prepares for another winter storm early next week, the T plans to shut down rail service on the Dorchester leg of the Red Line on Saturday to allow work crews to clear snow and repair tracks.

"For [Friday], sub-zero conditions and wind chills as low as minus 20 will likely affect aging trains' propulsion systems. While the MBTA will work hard to provide regular weekday service, customers are strongly encouraged to stay updated on delays and service interruptions via mbta.com or on twitter @mbta," reads a statement from the MBTA. "The MBTA apologizes for the inconvenience while crews work to restore service to the levels customers expect and deserve."

On Saturday, the Ashmont branch Red Line trains between JFK/UMass and Ashmont as well as Orange Line trains between Oak Grove and Wellington will be replaced with shuttle buses. The Braintree branch between JFK/UMass and Braintree will be replaced with shuttle buses on Sunday, February 8.

The agency also reports that the MTA in New York has "generously loaned the MBTA two jet-powered snow blowers (very similar to the MBTA's 'Snowzilla') to help clear the snow along the Red and Orange Line rights-of-way."