Ten minutes here and you'll read a storm setup like a chaser. Pro features are marked and included in your 7-day trial.
Create an account and open the app. Allow location when your browser asks, and the map will center on you and record your trail.
On a phone, use Share, then Add to Home Screen on iPhone, or Install app in Chrome's menu on Android, so it opens full screen.
No GPS? Tap the location label at the top, or long-press the map and choose I'm here.
The bar along the bottom shows your speed, heading, temperature, wind, elevation, tonight's low and nearby warnings. Radar loops on its own; the slider changes how see-through it is.
Long-press on a phone, or right-click on a computer, for Route here, Weather, Explore, Waypoint and Storm data. Switch to satellite or topo with the layers button in the top right.
Your exact spot blends the nearest stations and adjusts them to your elevation for the temperature now and tonight's low. Below that are storm ingredients, a 48-hour chart, the nearest official stations and the 7-day forecast.
Every NWS warning near you, with details like tornado observed or hail 1.75 inches, projected storm tracks, and the time each storm passes closest to you. Turn on Enable alarms for a sound and notification.
With Pro, radar cells show rotating storms: a diamond for a mesocyclone (a rotating supercell) and a triangle for a tornado vortex signature (tight rotation that can mean a tornado is forming). SPC mesoanalysis shows the Storm Prediction Center's live maps for your region.
In the Storms tab, choose Show on map, then Storms, Supercells or Tornado. Clear means nothing; green is low, then yellow, orange, red and purple for extreme. Drag the time slider to look ahead 24 hours. The target marks the best spot in view.
Tap anywhere on the map while it's on to see that spot's numbers.
| Number | What it means | Worth watching |
|---|---|---|
| CAPE | Fuel for storms | 1,000 J/kg and up; 2,500 is strong |
| Shear | Wind changing with height, which lets storms rotate | 40 kt and up |
| CIN | The cap that can stop storms from forming | Near zero means storms can fire |
| Cloud base | Lower bases favor tornadoes | Under about 3,300 ft |
| Supercell index | Supercell ingredients together, like SPC's SCP | 1 elevated, 2 high, 4 extreme |
| Tornado index | Tornado ingredients together, like SPC's STP | 1 and up is favorable |
StormTrail's indexes are estimates from free model data and leave out helicity. On a big day, check SPC's own maps in the mesoanalysis panel.
Open the Route tab and type where you're going, or long-press the map and choose Route here. The route is colored green, yellow or red by the forecast for the time you'll be there, with a chart of temperature, rain and wind and any warnings crossing it. Buttons along the bottom find fuel, camps, ghost towns and hot springs on the way.
Explore finds ghost towns, mines, ruins, oddities, hot springs and viewpoints from OpenStreetMap, including places most map apps don't list.
With Pro, Deep Dig sends the AI through Reddit, forums, blogs and history sites and pins every lead it finds, little-known places first. It takes a few minutes and keeps going if you switch tabs.
Ask in plain English: Where are the storms heading and are we safe? or Abandoned mines within 50 miles that aren't touristy. With Pro: Find the best supercell spot this afternoon, pin it and route me there. The panel shows each step it takes.
Each question uses one credit; a chase brief uses 3 and Deep Dig uses 10. Lite gets 15 a day and Pro gets 400.