Hi Cliff,
Yes things are wrong for you because Cumulus provide <#forecastnumber> "webtag"
as the only way to identify forecast by a number as we can't use forecast phrase as
they are too long to be used as icons filename.
In your case, you're using a "Mercedès" station with a far better forecast calculation system
and you're using these forecast instead of Cumulus own... the <#forecastnumber> based icon
library then correspond to nothing for you!
Sorry, I see no easy way to adapt these icons for your forecasts.
Regards,
Jacques