Cliff Mass is Professor of Atmospheric Sciences at the University of Washington. To those of us in the Seattle area, he's a weather celebrity, appearing every Friday on local public radio station KUOW to provide a weekend weather forecast and discuss other weather issues. His blog covers similar material, such as his explanation of why weather radar shows lots of echoes even though there was no rain.
His articles, while fascinating, are also quite long, so to help you get through them, there is the Cliff Mass TLDR blog. For example, the TLDR version of the mysterious echoes goes like this:
The radar is picking up birds instead of rain
It's been dry, but the weather radar last night showed lots of echos, suggesting it rained all night. No, it was just birds.
Explaining the joke in the title: "Cliff Notes" is a pun on CliffsNotes, a United States producer of study guides.