To illustrate the purity of the arctic air, following are the temperature plots from this morning from the source region, the Yukon and Northwest Territory Provinces of Canada and eastern Alaska.
|Surface temperatures at 10am MDT|
Looking further south the sub zero temperatures have spread across the border into northern Montana to the east of Glacier National Park.
|Surface temperatures at 10am MST|
|Noon Wednesday Nov 20 2013|
|6am Thursday Nov 21 2013|
|6am Friday Nov 22 2013|
The weekend should be clear and continued cold with some moderation, but still near zero at night in some locations.