Weather Geek Tweet. This graphic depicts the arctic airmass "signal" for Friday night. Without getting into too much detail, the tannish color is indicating that the forecasted airmass aloft only occurs 1 day every 10 years for this time of year. Serious Cold!! #mewx #nhwx pic.twitter.com/VjnImrq3zs

— NWS Gray (@NWSGray) January 29, 2023