How to read the 15-day outlook

The 15-day outlook is a daily forecast for a single airfield or city — one card per day, fifteen days out. It's the planning-horizon companion to the hourly meteogram: use it to answer “is next weekend even worth planning for?”, then drop into the meteogram and cross-section for the go/no-go once the day is close.

Two forecasts, two confidence levels

The outlook stitches together two different models, and the page keeps them visibly separate because the confidence is genuinely different:

• Days 1–5 (“Next days”): built from the same ICON-D2 / ICON-EU meteogram that drives the rest of the site, aggregated down to one card per day. High resolution, hourly under the hood, refreshed with every model run.
• Days 6–15 (“Extended”): from the ECMWF global model (IFS), extracted at your location. Coarser sampling (roughly four points per day) and lower confidence — this is a trend, not a promise.

The further out you look, the more you should read the outlook as a probability rather than a plan. A run of sunny glyphs on days 9–12 means “the atmosphere currently favours settled weather then” — not “book the flight”.

The card front

Each day's card shows, at a glance:

• Weekday & date at the top.
• A weather glyph summarising the dominant condition (sun, cloud, rain, snow, storm).
• Temperature high / low — the day's warmest and coolest 2 m temperatures.
• Dewpoint high / low (“Td”) — a quick read on humidity and how close the air is to saturating into fog or low cloud.
• Precipitation (💧) — the total for the whole day in millimetres. 💧 0 mm means dry.
• Wind — the day's peak sustained speed and gust (8G14 kt = 8 kt gusting 14), with an arrow and label for the prevailing direction. Prevailing here is the vector mean of the day's wind, so a wind that boxes the compass averages out to weak-and-variable rather than to a misleading single heading.

Tap a card for the day's detail

Tap (or click) any card and it flips to a back face with more than the headline numbers.

For days 1–5, the back breaks the daylight hours into Morning / Afternoon / Evening, each with its own temperature, wind (mean, gust, direction), cloud, and precipitation. Cloud is written the way the rest of the site and the watch face phrase it — METAR-style layers like broken 4,900 ft or overcast 1,000 ft — so you can see a low-stratus morning burning off to a scattered afternoon. Below the parts, an aviation footer gives the daytime ceiling, visibility (as min–max ranges, not a single number), freezing level, and a CAPE flag when thunderstorm fuel is present.

For days 6–15, the back shows the day's high/low, dewpoint, wind, cloud cover and rain total — the ECMWF data is too coarse for a trustworthy intraday breakdown, so it stays at daily resolution.

How the daily values are aggregated

The single-number card values come from the underlying hourly / sub-daily data:

• Temperature & dewpoint high/low: the max and min across the whole day.
• Precipitation: the total accumulated over the day (front card and the days 6–15 back). On the days 1–5 back, each Morning/Afternoon/Evening figure is the precipitation for that block only — the three roughly sum to the daily total on the front.
• Wind: peak sustained speed and gust over the day; direction is the vector-mean (prevailing) heading.
• Ceiling, visibility & freezing level: computed over daylight hours only. This is deliberate — overnight fog and low stratus (common in autumn and winter) would otherwise dominate the figures and make every day look un-flyable. Ranges are shown as min–max so you can see how much the day varies.

How to use it for VFR planning

The outlook is a triage tool for the days ahead, not a briefing. It's at its best for questions like “which of the next few weekends looks worth keeping free?” or “is that cross-country later this week even plausible?”. Once a day moves inside the 1–5 window and gets close, switch to the tools built for the go/no-go:

• The meteogram for the hour-by-hour picture at your airfield, including crosswind.
• The cross-section for what the sky looks like along a specific route.
• And always the current METAR/TAF and an authorised weather briefing before flight.

Update cadence & caveats

The days 1–5 band refreshes with every ICON model run through the day. The ECMWF extended tail is regenerated on the full 00Z and 12Z runs, so the long-range days update roughly twice daily. Long-range forecasting is inherently uncertain: expect the days 6–15 cards to shift run-to-run, and weight the near days far more heavily than the far ones.