Seattle Center (ZSE) recently published LTA-ZSE-21, Runway 5 Corridor – Redmond, OR.  The LTA and graphics for import into software platforms that utilize KML files are available for download at: https://mikekloch.com/home/central-oregon-aviation-safety/seattle-center-atc-information/

The first graphic below, depicts the Runway 5 Corridor in yellow. ATC is requesting pilots receive advisories prior to transitioning.  Each segment represents a stepdown area of an approach procedure. The green arcs are predictive step down areas of a visual approach to Runway 5. 

There are additional approach paths into Redmond ATC would like pilots to be aware of. The second graphic shows commonly used transitions and approach paths to Runway 23, and the third shows the approach path to Runway 29.  ATC is publishing these corridors/approach paths to increase pilot situational awareness when operating in the vicinity of an active approach path.  Operations within the depicted paths between the labeled altitudes, increases the probability of a conflict with an inbound aircraft.