Sudden stratospheric warming and the polar vortex has split. It was reported a week ago that the stratosphere above the north pole had suddenly warmed from -80C to -30C, disturbing the polar vortex. This is a pretty rare event, several years between each incident, and it may affect the weather many places in the NH for weeks. For much Europe it means cold weather. I'm a bit sceptical of forecasts several weeks ahead, but it seems real for this event. Southern Norway has already got stuck into a dry and cold spell with no end in sight. Here in Oslo we usually gets inundated with warm and wet Atlantic lows during winter, dumping a mix of snow and occasional rain. This winter has had a lot of snow, around 150 cm on the ground now in the forests near Oslo, and I think the snow is secured till early May this year. February will be the first month I've ever recorded without a single reading above 0C, and the cold seems to last at least until the middle of March.
In the high Arctic, however, it's very warm, with temperatures above freezing at the North pole where temperatures usually stay in the 30's below at this time of the year.