The polar vortex, a powerful phenomenon in the upper atmosphere that traps cold air near the Arctic, is poised to trigger icy conditions across the eastern United States. This happens as the vortex weakens and shifts south, allowing cold, icy Arctic air to sink and temperatures to drop to dangerously low levels. Next week, the eastern half of the country will be hardest hit, while some regions could see temperatures fall as much as 30 degrees below normal. This will be a significant change from the record warmth set during last year’s winter season. This has resulted in the impending severe, widespread cold event reaching most parts of the country.

Accordingly CNN, Temperatures will be the coldest of the winter so far and will be frigid even for what is already the coldest time of the year. The cold will be pervasive – more than 70% of the country’s population will experience subfreezing temperatures next week – and will last well into the month, increasing the likelihood of snow.

The first blast of cold air will reach the northern United States on Wednesday, with high temperatures in the single digits or teens expected for parts of Montana, the Dakotas and Minnesota. Cold air will spread south and east daily for the rest of the week and weekend. The West will largely avoid a significant cold, as has been the trend at least since the fall.

The National Oceanic and Atmospheric Administration (NOAA) has issued important messages on climate prediction. “A significant pattern change is expected across much of the country as an Arctic outbreak is expected to spread from the northern plains south and east, resulting in an exceptionally high probability of below-average temperatures across much of the East,” it said.

What is the polar vortex?

According to the United States National Weather Service (NWS), the polar vortex is a large area of ​​low pressure and cold air surrounding both poles of the Earth. It ALWAYS exists near the poles, but weakens in summer and strengthens in winter. The term “vortex” refers to the counterclockwise flow of air that helps keep colder air near the poles. In winter, the polar vortex in the Northern Hemisphere often expands, sending cold air south with the jet stream (see graphic above). This happens fairly regularly during the winter and is often associated with large outbreaks of arctic air across the United States. The cold outbreak that occurred in January 2014 is similar to many other cold outbreaks in the past, including several notable cold outbreaks in 1977, 1982, 1985 and 1989.