Top: Brightness temperature channel map of the NCPL region from EBHIS data at v = 16.85 km s⁻¹. The white dashed outline shows the coverage of the NCPL mosaic from GHIGLS. The solid white box shows the 15° square region within which T22 analyzed the GHIGLS H I data. Bottom: Dust optical depth map at 353 GHz, τ ₃₅₃, from Planck Collaboration XI (2014), with 1 K and 2 K contours of the brightness temperature map (top) overlaid in solid cyan. In both panels, red arcs show the location of the moving warm H I gas and the magenta square shows the position of AL143.4+24.8.