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Metro announced tonight that—-like D.C. public schools, the local and federal governments, and early voting—-it’ll be closed on Monday.

This is the first time Metro has canceled all service since 2003 during Hurricane Isabel. During more recent major storms, like 2010’s Snowpocalypse, the transit agency was able to keep its underground train lines running. So what’s different this time?

Electricity, according to Metro spokesman Dan Stessel. There’s too much of a risk that area power companies like Pepco and Dominion could stop providing power to the system and leave trains stuck in tunnels, Stessel writes in an email.

“If you play that out… power goes out… train needs to be evacuated… puts everyone, including emergency responders, at risk,” Stessel writes.

Metro might not be back after Monday, either. According to an announcement from the agency, no decision has been made on whether rail and bus service will return on Tuesday.