How much snow has to fall for NYC's subway to shut down?

FILE- A subway train travels on the elevated track over the snow covered streets in the Bronx borough of New York City. (Photo by David Dee Delgado/Getty Images)

A winter storm expected to hit the New York City area this week could dump several inches of snow and slow down the morning commute for many. 

In anticipation of snowfall, the Metropolitan Transportation Authority has a plan in place if subway and train service has to be shut down if there's a lot of snow. 

The agency is North America's largest transportation network and serves a population of 15.3 million people across a 5,000-square-mile travel area surrounding New York City, Long Island, southeastern New York State, and Connecticut, according to its website. 

How much snow has to fall for the subway to shut down?

The MTA says 12+ inches of snow, or blizzard conditions, will cause significant service suspensions or a full system shutdown is likely. You should only travel if it’s essential.

If there are subzero temperatures without precipitation, the agency notes that the subway will have regular or reduced service. Some express service might be suspended, depending on where the trains are parked to protect them from the weather. 

RELATED: Winter storm NYC: How much snow will NY, NJ, CT see?

According to the MTA, if there is ice, sleet, and freezing rain, commuters should be aware that there could be regular or reduced service. Some express service trains could be suspended, depending on where the subway trains are parked. 

How much snow is the New York area expecting?

By the pre-dawn hours of Tuesday, widespread snow is expected across portions of New York, making the morning commute for people heading to work quite tricky and dangerous, FOX 5 New York reported. 

Snow will continue throughout Tuesday and may begin to move away from the region during the evening commute.

New York City and areas on Long Island could see 6 to 10+ inches, with higher amounts locally possible. 

MORE: MTA updates, flight delays, travel advisories for Tuesday

FOX 5 New York contributed to this report. This story was reported from Washington, D.C.