Four hexagonal crystal habits and orientations made the display:
Random oriented columns (22* halo),
Horizontal columns (tangent, supralateral, infralateral and Wegener arcs),
Parry oriented columns (Parry and helic arcs).
Plate crystals (sundogs)
All crystals except randomly oriented ones help the parhelic circle shine.
Ski slope snow blowers were operating in the area. Tiny nuclei from these drift downwind and exquisite quality ice crystals grow slowly on them. They are quite natural - just helped a little by the extra nuclei provided.
A 'commonplace' 22° halo circles the low sun crossed by a bright white parhelic circle studded with a sundog.
But the show's stars are the arcs above the sun. A 'gull-wing' upper tangent arc and above that not one but two rare Parry arcs.
The strongly coloured arcs at left are supralateral and infralateral arcs crossing at the parhelic circle.
There are rarer beasts - see the labelled HaloSim ray tracing below.
The next OPOD has images by Sofia Andersson with more rare arcs.