Window informs; it doesn't decide.It shows the weather and the published reference lines — the 20 mph surface-wind limit, winds aloft, the ceiling — and leaves the go/no-go call to you and your range's rules. Every figure is best-effort and carries its source and valid time. Confirm conditions yourself before you fly.
How to read this
Pick a launch field and Window pulls the weather a flyer actually needs to decide whether to fly — fetched live in your browser, from the field you choose. It takes no rocket parameters and gives no verdict; it surfaces the data and the reference lines and lets you decide.
- Right now is the surface wind against the 20 mph NFPA/NAR/Tripoli launch limit — a reference line, never a go/no-go. Winds are named for the direction they blow from.
- Today & tomorrow is the hourly wind, with the upcoming calm windows (stretches under your line, day or night) surfaced above it. Tap a window, or drag the slider, to set the hour shown in the winds-aloft profile.
- Winds aloft is wind speed and direction by true height above the field, surface up to waiver altitudes — the thing general weather apps bury. Each pressure level is placed at its real height AGL.
- Sky & ceiling is the observed ceiling from the nearest reporting station where there is one, labelled observed, with a modelled multi-day cloud picture beside it.
- Units & sharing — toggle Imperial/Metric (and knots) any time; it never refetches. The field is in the URL, so a link is shareable and reload-proof. Saved fields, units, and your personal wind line stay in this browser.
- Offline— if a fetch fails or you lose signal, Window shows the last data it loaded for that field with an “as of” flag, never a stale reading dressed as fresh.
How this is derived
Every number on this page is fetched live from a free public provider, in your browser, for the field you chose. Here is where each one comes from, the model and valid time behind it, and where it can be wrong.
Surface wind, temperature & precip
From the Open-Meteo Forecast API, using a US-optimised GFS/HRRR blend (gfs_seamless), requested in imperial units. The current reading carries its own valid time; it's a model analysis, not a station observation, so a gusty or terrain-affected field can differ from what you feel at the pad. Winds are the direction the air comes from.
The 20 mph line
NFPA 1127 and the NAR/Tripoli safety codes set 20 mph as the surface-wind ceiling for launching. Window draws it as a reference and colours the current wind as it approaches and crosses it — but it never says no-go. The call is yours, with your field's rules and your own judgment. A personal, lower line can be set and is stored only in your browser.
Winds aloft (the profile)
Open-Meteo pressure-level winds (1000 down to 250 hPa) for the selected hour. Each level is placed at its true height above the field: the level's geopotential height minus the field's ground elevation (Open-Meteo's reported elevation for the coordinates). Levels below the field are dropped. This is a model profile — resolution thins with altitude, and a real sounding can differ — but it's the best free upper-air data available, since NOAA retired the public RAP/rucsoundings feed for the continental US.
Cloud ceiling & sky
The observed ceiling is the lowest broken or overcast layer from the nearest NWS reporting station's latest observation (a METAR), converted to feet; the nearest automated stations that report no cloud layers are skipped. It's labelled observedand stamped with the station and how long ago it reported. The multi-day sky picture and the fallback when no station is reachable are Open-Meteo's modelled cloud cover, labelled modelled. A forecast ceiling in feet (TAF) is planned for a later version — its source has no browser access today.
Active alerts
NWS active watches, warnings, and advisories for the field (/alerts/active), most severe first. NWS is a best-effort enhancement: if it can't be reached, alerts and the observed ceiling are simply absent rather than shown as an error, and the sky falls back to the modelled cloud cover.
Calm windows
The hourly forecast already knows when the wind lays down, so Window surfaces the upcoming stretches where the sustainedwind stays at or below your line (the 20 mph reference, or a lower personal one), scanning the next two days from now. Each window shows its peak wind and gust and whether it falls in daylight (Open-Meteo's day/night flag). It is plain aggregation of the hourly numbers against a line you chose — it highlights low-wind daylight stretches, it doesn't tell you to fly.
Multi-day outlook & daylight
Open-Meteo daily aggregates for ~7 days: high/low temperature, the day's maximum sustained wind and gust, dominant wind direction, peak precipitation probability, mean cloud cover, and sunrise/sunset (field-local — for planning setup and leaving daylight for recovery). A day whose max wind crosses 20 mph is marked — again as a reference, not a verdict.
Freshness, caching & offline
A field is fetched once and cached in your browser for about ten minutes, so a reload or a units change doesn't refetch. If you're offline or a fetch fails, Window shows the last data it successfully loaded for that field, with a prominent “as of” staleness flag. The service worker caches only the app shell for instant load — it never caches a forecast, so freshness is always real.