By Paul Dorian (perspectaweather.com) – Re-Blogged From WUWT
12Z GFS forecast maps of 500 mb height anomalies show strong ridging from Alaska to the west coasts of Canada and the US both late this week (left) and early next week (right). This type of upper-level air flow will allow for the transport of these next couple of Arctic air masses from northern Canada into the central and eastern US. Maps courtesy NOAA, tropicaltidbits.com