Where do Slopes' snow forecasts and conditions come from?

This season, Slopes makes its own snow forecasts and conditions reports for more than 1,000 resorts around the world. They're free for everyone, on iPhone and Android.

What goes into them

• Weather models: forecasts for snowfall, wind and temperature at each resort. Because no forecast is certain, Slopes shows snowfall as a range, along with how likely each amount is.
• Reports from Slopes users: people vote on what it's like on the snow, like icy, groomed, wet or granular. Slopes combines these votes with recent weather to write a short summary of what it's like on the snow, and to show how conditions are changing over time.

• SNOTEL stations, where there's one nearby. These are automated stations, common in the western US, that measure how much water is in the snowpack. Many have been running for more than 30 years, so we can compare this season with past ones.

Every resort also shows an estimate of how much snow has fallen over the last 30 days.

Why are the numbers different from another app?

Forecast services use different weather models, so their numbers won't always match. Slopes also counts each day's snow from 4pm rather than 6am, which can make daily totals look different.

Why can't I see conditions?

Conditions need an internet connection to update. If the information is too old to be useful, Slopes hides it rather than showing you an out-of-date report. Try again once you're connected.