Flyfun Weather — the weather briefing tool for GA I wanted, with a European bias...

Hi all,

I’ve been working on a weather briefing tool for cross-country GA flying and thought I’d share it in case it’s useful to others (I am hoping so). It’s called Flyfun Weather and it’s free to use at weather.flyfun.aero.

Why I built it: I fly cross-country across Europe quite a bit, and the pre-flight weather ritual was getting tedious: flipping between Windy layers, pulling GRAMETs from Autorouter, checking ForeFlight, trying to mentally compare what different models say about icing, clouds, and convection at different altitudes. I kept thinking: why am I doing this manually every time? So I started building a tool that pulls all of it together automatically and produces advisories that consolidate what I was piecing together by hand. Along the way I went down the rabbit hole of Skew-T diagrams, thermodynamic indices, and the different methods used to predict icing and clouds from model data. It’s genuinely fascinating stuff, and I wanted the tool to expose that richness rather than hide it.

I also wanted something that works well for European flying: comparing multiple NWP models (GFS, ECMWF IFS, DWD ICON, Météo-France, UK Met Office) along your route, with data you’d normally have to piece together from several sources.

What it does:

- Route advisories — icing, convection, cloud ceilings, turbulence, crosswinds — rated green/amber/red per model so you can see where forecasts agree and where they don’t. An altitude advisory suggests the best flight level considering all conditions.
- Interactive cross-sections — vertical slices along your route showing clouds, icing, wind, humidity across multiple layers. A compare view overlays all models on the same layer.
- Skew-T soundings at every waypoint and interpolated points along the route, per model.
- METAR/TAF section appears on the day of the flight for a final cross-check.
- AI synopsis — an optional LLM-generated plain-language summary of the weather situation.
- Compact and full detail modes: quick overview or dive into all the raw numbers.

It’s designed mainly for D-7 to D-0 planning — helping you build a picture of how weather is evolving before a flight, not as a replacement for your official briefing.

Data sources: Most forecast data comes from [Open-Meteo](https://open-meteo.com/), which I also enrich with raw GRIB data from GFS and DWD ICON for additional variables like cloud water content and icing indices that aren’t available through the API. One frustration: ECMWF IFS is arguably the best model, but the freely available data has the fewest pressure levels (13 vs 28 for GFS) — which limits the vertical detail in soundings and cross-sections. I may look into what the full-resolution ECMWF data would cost to access.

What it is not (yet):

This is an early-stage personal project. It’s not certified, not a replacement for official sources, and there are plenty of rough edges. I’m a pilot and developer, not a meteorologist — so the interpretations may not always be perfect. That’s actually one reason I expose all the raw data: so you can form your own judgment rather than relying on a black box.

The advisory tuning and model selection are geared toward European conditions — DWD ICON and Météo-France ARPEGE have much better resolution over Europe than GFS alone — but it works globally.

I’d love feedback:

If you give it a try, I’d genuinely appreciate hearing what’s useful, what’s confusing, and what’s missing. There’s a feedback button on the briefing page, or you can reach me here. The project is open-source on [GitHub](https://github.com/roznet/flyfun-weather) if you’re curious about how it works. I also run it currently on a small server, so it can be a bit slow, but if enough people like it and it becomes a bottleneck, i can easily upgrade it.

I’d also particularly welcome discussion around the weather models and methods themselves — how different icing prediction approaches compare, when one model tends to be more reliable than another in certain regions, that sort of thing. Part of why I built this was to learn, and I’d love to hear from pilots or meteorology enthusiasts who have insights on this.

Hope this can become something genuinely useful for planning. Happy flying.

PS: here is an example of a briefing for a flight I actually did, if you want to see what it looks like.