During mid-January, an arctic air mass formed in Northern Canada and Greenland. After the arctic air mass formed, a sudden stratospheric warming (SSW) episode emerged over Canada. The warming and expanding stratosphere quickly compensated for by a cooling troposphere beneath, as a polar vortex formed in central North America.

A drying soil moisture trend is established across parts of West and Southwest Russia into Eastern Europe plus west/southwest Italy to Portugal and Northwest Africa. Last week, a very dry pattern stretched across most of Europe and Western Russia. The dryness is attributed to general high pressure aloft downwind a large marine heatwave in the east/northeast North Atlantic. The 15-day outlook maintains dryness across Eastern Europe and Southwest Russia.

During December, La Nina onset emerged as both the surface and subsurface equatorial East Pacific shifted very cool. However, since that time, a transient Madden Julian oscillation (MJO) weakened the upwelling trade winds across the eastern equatorial Pacific and surface waters have warmed to borderline La Nina conditions in the Nino34 SSTA zone.

As the weekend begins, a plethora of weather watch, warnings, and advisories are issued with many more ahead into early next week. Currently, an Extreme Cold Warning is issued for the northern Great Plains. In the warning area, temperatures routinely collapse to -20F (or colder) with wind chills of -40F (or colder) by Monday morning. A Cold Weather Advisory is issued into the central Great Plains, certain to expand southward later today.