How to read it
IMS is an analyst-produced snow and ice presence analysis. The source chart's own legend and annotations define the displayed classes. It is not a snow-depth map, snowfall forecast, road-condition map, or ice-thickness estimate. North America may be analyzed more frequently operationally, but this viewer uses the published daily chart filename.
Why this stays current without infrastructure
The browser displays the authoritative USNIC image directly. It first tries today's UTC product filename, then falls back through the previous five days if today's chart has not been posted yet. No cross-origin response is parsed, so CORS is not required. There is no API endpoint, key, token, serverless function, proxy, or scheduled GitHub refresh.