The chances of heavy snowfall in the region this weekend are increasing.

The Pittsburgh office of the National Weather Service in a social media post said the notion that the region could see no snow this weekend “has been completely thrown out.” The most likely model now predicts more than six inches is likely to blanket the area, with up to 15 inches possible in the mountains.

Exactly how much precipitation pummels the region depends on how the storm moves.

In what the National Weather Service dubbed the “southern track scenario,” the storm track would form to the south and curve north as it heads to the mid-Atlantic region. If that happens, meteorologists predict the region would see between one and six inches of accumulation.

That scenario, officials said, is seeming less likely. The National Weather Service said there’s about a 25% chance that happens.

The more likely outcome — the “northern track scenario” — would see the storm forming to the south, then curving up the spine of the Appalachians and reforming off the coast.

The local National Weather Service said there’s a 75% chance that’s what happens.

If they’re right, much of the area would likely see more than six inches of snow, with 15 inches or more possible in the mountains.

Snowfall is likely to start late Saturday and last through the day Sunday, according to TribLive news partner WTAE. The heaviest precipitation will likely come overnight Saturday into Sunday morning, and travel may be difficult.

In a social media post, the service said people should start preparing for the possible winter storm. They urged anyone with travel plans over the weekend to begin thinking of contingencies. And people staying inside should stock up on emergency supplies, like food, batteries, water and portable chargers.

Officials also encouraged people to check smoke detectors and top off fuel for cars and heating sources. Anyone with electric heating should have alternate plans to stay warm in case they lose power.

“This storm will be followed by an extended cold period, so that snow will not be going anywhere,” the National Weather Service wrote on social media. “With cold and snow, next week may be a period where you’d want to avoid extended periods outdoors.”

A winter storm watch will likely be issued.

The snowstorm follows a frigid week that saw wind chills plunge to subzero temperatures Tuesday. It was cold enough earlier in the week for an ice blockage to threaten operations at a Pittsburgh Water treatment plant.