Christmas storm shows signs of stopping, but reportedly leaves at least 50 dead and millions without power in its wake

• A massive US winter storm reportedly left at least 50 dead and millions without power.
• The National Weather Service warned of "potentially life-threatening" conditions across the US.

The massive winter storm sweeping across the US over Christmas will slowly let up as it heads east, the National Weather Service said, but the death toll and damage remain extensive, and the danger for many remains.

The National Weather Service issued an updated forecast on Sunday saying the storm would weaken as it progressed eastward, while still warning of "potentially life-threatening" conditions that could cause frostbite in minutes.

The extreme weather conditions left more than one million without power on Friday. By Sunday, more than 140,000 people across Maine, New York, Virginia, Washington, and New Hampshire were still experiencing power outages, according to the .

As of Sunday morning, more than 55 million people were under wind chill alerts, per CNN. Near Buffalo, New York, officials braced for more dangers to come with many still trapped in the deadly conditions.

The storm would be remembered as the "most devastating storm in Buffalo's long storied history" New York Gov. Kathy Hochul told CNN on Sunday. "It's a crisis of epic proportion."

Conditions proved fatal in much of the country. A three-vehicle crash in Ohio's Franklin Township on Saturday increased the weather-related death toll to 27. And by Monday, the toll had risen to at least 50 people, NBC News reported.

Travelers hoping to make it home for the holiday were plunged into chaos on Friday afternoon when more than 4,500 flights were canceled and more than 6,000 delayed as the winter storm engulfed the central and eastern US.

On Christmas day, there were more than 3,100 cancellations and over 7,700 delays involving flights to, from, or within the US, according to the flight-tracking site FlightAware.

The snow and cold are expected to move through the midwestern US according to the National Weather Service, which said that "much of the eastern U.S. will remain in a deep freeze through Monday before a moderating trend sets in on Tuesday."