With an NWS forecast of 4 degrees for #Denver Tuesday morning, I just HAD to see where that air emanated from. Here's the GFS 5-day back-trajectory forecast at 500m verifying Tuesday morning. That's about as straight out of the frozen north as it gets. #winter #cowx pic.twitter.com/Khm0QgKCxw

— Tom Niziol (@TomNiziol) October 25, 2020