Colour Bar Builder

The preview is not a simulation. It is the published HRRR raster with its palette rewritten to your stops — the same 387-byte splice the map viewers do — so what you are looking at is real forecast data in your candidate colours, at full resolution.

That is the point of building a colour table here rather than in a gradient picker. A ramp is not judged as a strip: it is judged on whether a front reads, whether freezing lands where the eye expects it, whether a reflectivity core separates from the shield around it. A bar that looks handsome can be useless on a map, and there is no way to tell until you put it on one.

Give it the units of a field and the ramp is read at that field's real values — your 32 °F colour lands on freezing. Leave units blank, or use a unit the field does not have, and it is stretched across the field's range instead. The badge above the preview says which is happening.

Nothing is written to the server. The page hands you a JSON file in the same frozen-stops schema ingest/import_ramp.py writes, hash and all; drop it in data/ramps/ and deploy. Colour tables change by review, not by web request — the palette is the value encoding, so a table that could be edited remotely could silently change what every readout reports.