Guide
How to get the most from Gradient WX
Everything you need to read a mountain or sea forecast with confidence: how to use the site, what each weather model is, what every number on the page means, and how to check which model has been right.
4 steps to a forecast
24 weather models
3 views forecast, detail, history
1 check of who was right
On this page
Getting started
Four steps to a forecast
1. Location
Search for a resort, mountain, town, marina or sailing club, tap anywhere on the map, or use My location. In Mountains mode, ski resorts and peaks come first in the search.
2. Choose your adventure
Mountains is set up for snow: snowfall, freezing level and wind at height. Sea is set up for sailing: wind, gusts, waves, swell, tides and pressure, all at sea level.
3. Elevation
Set the height you care about. Every forecast is corrected to it, because the air usually cools by about 6.5 °C for every 1,000 m you climb. Pick a ski resort and you get Top, Middle and Bottom buttons.
4. Models
Most accurate here picks the models that have matched the nearest weather station best. My choice uses the models you tick in Models & settings.
Three ways to look at it
Forecast, Full detail and Snow history
- Forecast One model, laid out simply: weather symbols, wind, snow, rain and temperatures by time of day, with a running total chart across the top. Choose the model at the top, and tap Choose what’s shown to add or remove rows.
- Full detail Every model side by side, hour by hour, with the average of all of them at the top. Use it to see how sure the forecast is: when the models agree, trust it more.
- Snow history A normal year, week by week, from 15 years of past weather: when the snow usually comes, how much falls as snow rather than rain, and the freezing level through the winter. Ski resorts get top, middle and bottom lines.
- Length How far ahead to look, from 24 hours to 14 days. The first two or three days are the most reliable.
The map
The map and 3D view
- Show on map Loads the chosen weather for the area you can see, shaded by the height of the ground. Tap any spot for its numbers, then Forecast or Full detail.
- Snow total, Rain total, All precipitation How much falls over the period you choose (next 24 hours to 7 days, or the past 24 hours to 7 days).
- Temperature, Freezing level, Wind, Cloud Conditions at one moment. Drag the time slider under the map, or press Play.
- 3D view Tilts the map to show the mountains with the weather draped over them. Drag to move, pinch to zoom, twist to turn, and use the panel on the right to tilt, turn, zoom and face north.
- Resorts Every ski resort as a dot when you are zoomed out (hover or tap for its name), and as a label with its top and bottom height closer in. Tap one for its forecast.
- Ski runs Runs and lifts: green, blue, red and black in Europe; green, blue and black in North America, Australia and New Zealand.
- Webcams Live cameras near you when you zoom in, with their height, a timelapse and full screen.
- Base The background map: muted, bright, grey, street map or satellite. It doesn’t change the weather colours.
Reading the forecast
What the numbers mean
Snow and rain
- Snow (cm) Fresh snow expected at your height. It is worked out from the water that falls and the temperature: colder air makes lighter, deeper snow.
- Rain (mm) Water falling as rain at your height. 1 mm of rain is roughly 1 cm of snow had it been cold enough.
- Freezing rain Rain falling into air below 0 °C, which turns to ice on contact. Dangerous on roads and slopes.
- Running total chart Snow (blue), rain (green) and freezing rain (red) added up over time. Hover or touch it for the totals at any moment.
Temperature and the snow line
- Freezing level The height where the air is 0 °C. Below it you get rain; above it, snow.
- Snow line Usually a few hundred metres below the freezing level, because snow takes time to melt as it falls.
- Feels like What the temperature feels like on your skin, with the wind and humidity taken into account.
- Max and Min The highest and lowest temperature in each period, at your height.
Wind and sea
- Wind The average speed, with an arrow showing where it blows to. The colour runs from blue (calm) to red (strong).
- Gusts The strongest short bursts. On ridges and at sea these matter more than the average.
- Waves and swell Waves are the total sea state; swell is the longer waves from far away. The number in seconds is the time between waves: longer means more powerful.
- Tides High and low water from the marine model. Always check official tide tables before going afloat.
Everything else
- Weather symbol Sun, cloud, rain or snow for the period, worked out at your height.
- Humidity How much moisture is in the air, in %. Near 100% often means cloud or fog.
- Cloud cover How much of the sky is covered, in %.
- Pressure Air pressure at sea level in hPa. Falling pressure usually means worsening weather.
The models
The weather models
A weather model is a computer simulation of the atmosphere, run by a national weather service several times a day. Each one starts from slightly different measurements and splits the world into a grid of squares: the smaller the squares (the detail), the better it sees mountains and valleys, but the shorter it usually looks ahead.
Tip: use a detailed local model for the next one or two days, and the global models (ECMWF especially) for further ahead. When the models disagree, the weather really is uncertain: plan for the range, not one number.
Detailed local models
Shown only where they cover your location. Best for the next day or two in the mountains.
| Model | From | Detail | Looks ahead | Covers | Good for |
|---|---|---|---|---|---|
| MeteoSwiss ICON-CH1 | Switzerland | 1 km | about 1½ days | The Alps | The finest detail in the Alps: valleys, ridges and local snow showers |
| MeteoSwiss ICON-CH2 | Switzerland | 2 km | about 5 days | The Alps | Detailed Alpine forecasts a few days ahead |
| DWD ICON-D2 | Germany | 2 km | 2 days | Central Europe and the Alps | Thunderstorms and short, heavy snow showers |
| GeoSphere AROME | Austria | 2.5 km | about 2½ days | The Alps and Austria | Austrian and eastern Alpine valleys |
| Météo-France AROME HD | France | 1.5 km | about 2 days | France, the Alps and Pyrenees | French Alps and Pyrenees, sudden storms |
| ItaliaMeteo ICON-2I | Italy | 2 km | about 3 days | Italy and the southern Alps | Italian Alps, Dolomites and Apennines |
| UK Met Office 2 km | UK | 2 km | about 2 days | UK and Ireland | Scottish hills and UK coasts |
| MET Norway Nordic | Norway | 1 km | about 2½ days | Scandinavia and the Baltic | Norwegian, Swedish and Finnish mountains and coasts |
| DWD ICON-EU | Germany | 7 km | 5 days | Europe | A good all-round European model |
| NOAA HRRR | USA | 3 km | 18 hours to 2 days | USA | Storms and snow bands in the next day or two |
| Canada HRDPS | Canada | 2.5 km | 2 days | Canada and northern USA | The Rockies and Coast Mountains |
| Canada RDPS | Canada | 10 km | about 3½ days | North America | North American storms a few days ahead |
| JMA MSM | Japan | 5 km | about 2–3 days | Japan | Japanese sea-effect snow |
| KMA LDPS | South Korea | 1.5 km | 2 days | Korea | Korean mountains |
Global models
They cover the whole world and look further ahead, but with less detail, so they smooth out the mountains.
| Model | From | Detail | Looks ahead | Good for |
|---|---|---|---|---|
| ECMWF IFS | Europe | 25 km | 15 days | Usually the most reliable model worldwide, especially 2–10 days ahead |
| ECMWF AIFS (AI) | Europe | 25 km | 15 days | An AI model trained on decades of weather; very good with the big picture |
| NOAA GFS | USA | 13 km | 16 days | Popular and free worldwide; reliable for the next week |
| DWD ICON | Germany | 13 km | about 7 days | Strong in Europe, good detail for a global model |
| UK Met Office Global | UK | 10 km | about 7 days | One of the best global models, especially for the Atlantic |
| Canada GEM | Canada | 15 km | 10 days | Useful extra opinion, good in North America |
| Météo-France ARPEGE | France | 25 km | about 4 days | Extra European opinion |
| JMA GSM | Japan | 55 km | about 11 days | Broad picture in Asia |
| BOM ACCESS-G | Australia | 15 km | 10 days | Australia and New Zealand |
| CMA GRAPES | China | 15 km | 10 days | Asia |
Average of all models: in Full detail, the top row averages every model you have chosen. Over time, the average is often closer than any single model.
Who was right?
The accuracy check
Gradient WX compares what each model forecast one day ahead with what the nearest suitable weather station actually measured. The station is chosen for being close and at a similar height, and each forecast is worked out for the station’s own height, so it’s a fair test.
Each model gets an error score for temperature, wind and precipitation, compared with the average of all the models. The lowest score ranks first, and Most accurate here uses the winners.
How to use it
1. Choose Most accurate here in step 4.
2. Pick Judged over and Judge on.
3. Open Full detail and scroll to Model accuracy for the scores.
- Judged over The past 7 or 30 days shows who is doing well in the current weather pattern; over the last year, or this time last year, shows who is reliable in general or in this season.
- Judge on What matters to you. Auto judges mountains on snow and rain and the sea on wind. You can choose wind, rain and snow, temperature or everything.
- Show Use the best model only, or the best 3 or 5. Using a few is usually safer than trusting one.
A model that scored well last week isn’t guaranteed to be right tomorrow, and a station can be sheltered or misread. Use the check as a guide to which models to trust a little more.
Saved spots and your account
Tap ☆ Save spot next to a forecast’s name to keep it. In Saved spots, tap ⌂ to make one your home: the site opens there. Without a home spot, it opens at the ski resort with the most snow forecast. Sign in with your email (no password) to keep your spots and settings on every device.
Sharing a forecast
Copy link makes a short link to exactly what you are looking at: the place, height, models and view. Send it to friends before a trip.
Questions
Frequently asked questions
Why is this different from the ski resort's own forecast?
Resorts often use one model, or a forecaster’s summary, for one height. Gradient WX shows every model at the exact height you choose. Compare the models: if most agree with the resort, you can be fairly confident; if they don’t, the weather really is uncertain.
Which height should I choose?
The height you’ll be skiing or walking at. For a resort, use Top, Middle and Bottom to see how the snow line cuts through it. Snow can fall at the top while it rains in the village.
Why does the map look blocky when zoomed right out?
Far out, the map loads fewer points to save data, then fills in detail when you stop. Press Show on map, or choose a higher Detail, to load more.
Why is the snow history for Japan lower than I expected?
The past-weather data (ERA5) smooths out mountains and under-counts heavy snow blowing in off the sea, so the amounts read low there. The share falling as snow is still reliable, which is why the chart shows that.
Do I need an account?
No. Everything is free without one. Signing in only keeps your saved spots, home spot and settings on all your devices.
The page says the weather service is busy. What do I do?
The free weather service limits how many requests anyone can make each minute. Wait a minute and try again. Loading a smaller area, or fewer models, uses less.
Ready?
Find your next powder day
Something unclear, or a forecast that looked wrong? Tell us and we’ll improve the guide.