If you ever wanted to explain extreme Arctic blocking to someone who is a complete novice with weather, tell them that it's warmer along the coast of Greenland at 7 AM in the morning than it is in Philadelphia.
Nuuk, Greenland, is the spot on the map that has a 36 degree temperature at this hour. It's located at 64 degrees North latitude, just below the Arctic circle, but its average high for today is 26 degrees. It's already ten degrees warmer than average as of 8 AM their local time (they are two hours ahead of us).
Here in Philadelphia? 29.
Extreme blocking patterns, such as the one that's in place over the Arctic and over Greenland, allow warmth to build aloft and at the surface in areas where high pressure is in control, resulting in milder than average conditions for the higher latitudes. A negative AO or NAO pattern puts these ridges of high pressure over the higher latitudes and dumps colder air south as it is displaced.
Even though the graphic below is a few days old, the pattern is still the same by and large. Greenland and the Arctic Ocean are experiencing above average temperatures while Canada and the northern parts of the United States are dealing with colder weather.
This pattern will likely continue through the end of March, although with the exception of Monday (perhaps) we should avoid any more days with highs south of 40. That said, it is a rather cold pattern for us for this time of the year and will shape our coldest March locally since 2005 once all is said and done.