Temperatures will drop by 15-20C with heavy rain and snow predicted in some states

Much of the US is bracing for a severe cold spell this week with temperatures set to plummet. In some places maximum temperatures are expected to drop by 15-20C over just a couple of days in contrast to above average temperatures in parts of the US earlier last week.

The rapid change in conditions is due to winds in the upper atmosphere weakening and meandering. At about six miles above the Earth’s surface there is a strong circulation known as the polar vortex around the north pole, which usually helps to keep cold air trapped there. However, late last week and early this week the circulation has been weakening and meandering, allowing a cold plume of air to be brought in from the north. Temperatures across central and eastern parts of the US are forecast to be 10-15C below average, with New York likely to see temperatures struggling to get out of negative double digits during daytime. As the cold air pushes in from the north, an area of low pressure will develop in the warmer gulf of Mexico, these two air masses will then clash across states bordering the Gulf of Mexico, bringing heavy rain and snow to areas that rarely see any. This cold spell is expected to last until the weekend, when temperatures will slowly start returning to around average.