HRDPS at 0.5° step previously dropped its lat=50 row inside HRRR's lon
range, so its first painted cell sat at lat=50.5 (halfStep=0.25 →
50.25°N). HRRR's top row at lat=50 paints to 50.0625°N. The ~0.19°
(~21 km) blank strip between them was visible on /weather wherever the
viewport crossed the US-Canada border.
Make in_conus_bbox exclusive on the north edge (lat < LAT_MAX) so the
boundary row stays in HRDPS. The merge_prefer_hrrr layer dedupes by
exact (lat, lon) on the merged read path, and the canvas overlay paints
HRRR above HRDPS, so the new overlap is invisible everywhere HRRR has
data.
Won't take effect on prod until the next HRDPS chain run produces fresh
chunk files.
Graham McIntire
b14c87126c