Today’s weather feature: Frazer River Outflow

If you are into the specific weather features of the PNW then you know about the Frazer River Outflow.  This is the main geological/atmospheric feature that is allowing this cold arctic air to flow into Washington state.  Add another high pressure system in the Gulf of Alaska and well; cold dry weather for the Cascades.

The Frazer River flows between the Coastal Mountains of BC and the Canadian Rockies forming and impressive feature called the Rocky Mountain Trench.  When a large high pressure system develops over the interior northwest (Montana, Alberta, Saskatchewan…) it pulls cold arctic air down through the river valleys of the Frazer, Thomson and Columbia Rivers.  The “Trench” creating the Frazer River Outflow. 

Note all the cold (blue) air with NE gradients.