POLAR VORTEX

The wind chill on Mount Washington in New Hampshire crashed to at least 108 degrees below zero Friday night.

Senator Tina Smith calls for investigation into gas price hikes during Arctic freeze After the Polar Vortex descended on the U.S., natural gas customers began to see price hikes of up to 100 times normal rates. Senator Tina Smith of Minnesota joins CBSN to explain why she's calling for an investigation into possible price gouging.

ORLANDO, Fla. – The northern tier of the country has been in the grasp of Arctic air for the last week. The core of the potentially record-breaking cold air will settle right into the Nation’s heartland over the weekend. The second is the stratospheric polar vortex which forms in the winter and resides over the polar regions way up in the stratosphere. When the stratospheric polar vortex is weak, the tropospheric polar vortex or polar jet stream also tends to weaken, allowing for Arctic air to spill into the Lower-48. (NOAA)The Arctic oscillation tracks the stability of the polar vortex.

The Arctic air is already invading the Upper Midwest, with temperatures expected to be below zero by Saturday morning from Montana to Wisconsin. On Sunday, the cold air will penetrate further south and east into the Great Lakes and mid-Mississippi Valley. CBS NewsThis push of Arctic air is due to a rather convoluted pattern across the Arctic and Polar regions, which started to evolve in early January. That block forces the jet stream to steer around it and the cold air is displaced south from the Arctic to the mid-latitudes. A graphic showing colder air being pushed into the northern U.S. CBS NewsThe cold air doesn't always land in the same locations.

Weather forecast: Return of the Polar Vortex? Big changes in the weather are coming for millions of Americans next week. The West will get extreme heat, while the East and Midwest could see a return of the Polar Vortex. Megan Glaros of CBS affiliate WBBM reports.