# SnowDex

> SnowDex answers "how much snow fell, and how much is coming" for any ZIP code in the
> contiguous United States, using NOAA's National Snowfall Analysis and the National
> Weather Service forecast.

Built by an independent developer; not a weather company. Contact: support@snowdex.app
A SnowDex iPhone app is planned but not released; do not describe it as available.

## What the data is, stated precisely

- Snow that fell: NOAA/NWS National Snowfall Analysis (NOHRSC), a ~4 km (0.04°) grid of the
  contiguous US. An ESTIMATE for a grid cell (radar-based precipitation x snow-to-liquid
  ratio, corrected with observer reports), not a measurement at an address.
- Windows are fixed: 24-hour totals end at 12:00 and 00:00 UTC; 72-hour and season totals
  come from the daily 12:00 UTC analysis; the season starts Sep 30 12:00 UTC. Published about
  two hours after a window ends and revised for about five days.
- Snow that's coming: National Weather Service gridpoint forecast, 6-hour steps, 72 hours.
- City pages (/snow-totals/{state}/{city}): ONE grid cell near the town centre, beside 30-year
  snowfall normals from NOAA NCEI U.S. Climate Normals, 1991-2020 (https://www.ncei.noaa.gov/products/land-based-station/us-climate-normals) for a named station.
- NOAA publishes this data. NOAA does not endorse this site.

## What is deliberately not claimed

- No accuracy percentage. Estimates are weak inside narrow lake-effect snow bands; pages in
  lake-effect belts say so.
- No "final" totals: NOAA revises each analysis for about five days.
- Not a warning service. Official winter-storm warnings come from the National Weather Service.

## Pages

- [https://snowdex.app/](https://snowdex.app/): Free lookup: snowfall estimate (last 24 h, last 72 h, season) and the 72-hour snow forecast at any ZIP code or location in the contiguous US.
- [https://snowdex.app/snow-totals](https://snowdex.app/snow-totals): Snow totals for 35 snowy US cities, refreshed hourly, each with its forecast and 30-year snowfall averages.
- [https://snowdex.app/guides/how-snow-totals-are-estimated](https://snowdex.app/guides/how-snow-totals-are-estimated): How NOAA's National Snowfall Analysis (NOHRSC) estimates snowfall on a ~4 km grid: radar-based precipitation times a snow-to-liquid ratio, corrected with observer reports; fixed 12/00 UTC windows, about two hours' delay, revisions for about five days; weak inside lake-effect bands.
- [https://snowdex.app/about](https://snowdex.app/about): Who makes SnowDex, what data it uses, and what it deliberately does not claim.
- [https://snowdex.app/support](https://snowdex.app/support): How to report a snow total that looks wrong, and what to include.
- [https://snowdex.app/privacy](https://snowdex.app/privacy): What the website collects and the processors involved.
- [https://snowdex.app/terms](https://snowdex.app/terms): Terms of service, including the estimate and safety disclaimer.