We proudly welcome the oncoming polar vortex tomorrow evening:
The polar vortex is an area of cold low pressure that typically circulates around the Arctic during the winter, spreading tentacles of cold southward into Europe, Asia, and North America at times. Except this time, it’s not a small section of the vortex, but what one forecaster, Ryan Maue of WeatherBELL Analytics, called “more like the whole enchilada” [that's visiting the eastern U.S.]
The Chicago Weather Center predicts starting Sunday night “a non-stop 60 hour stretch of temperatures which fail to break above 0-degrees” – the longest such period of the past 18 years.
The core of the cold reaches the Ohio Valley and East Coast Monday night into Tuesday, when temperatures drop 20 to 40+ degrees below normal.
The cold air will slowly begin retreating Wednesday.
Here are the temperature, wind, and precipitation probability graphs for the next 48 hours (click for full size):
The next 48 hours look almost as bleak, with the temperature line staying below -18°C until around midnight Wednesday. Strangely enough, it just keeps going up from there, hitting the freezing mark on Friday morning.
So: two days of the coldest air anyone has experienced in Chicago since the 66 hour stretch we had in February 1996.