An Socach (Braemar): Thursday 5 November 2026 to Wednesday 11 November 2026
Morning valley fog may recur on these dates. Separate daily possibilities, not continuous fog. Check the timing and confidence for each date.
What is a cloud inversion?
Normally, air becomes colder with height. During a temperature inversion, a layer of warmer air sits above cooler air near the ground. Moisture can become trapped below that warmer layer, filling valleys and glens with cloud while higher summits remain clear.
When are inversions most likely?
Look for settled high pressure, light winds and long clear nights, especially in autumn and winter. Cold air drains into valleys overnight, while drier air above may remain warmer. A strong inversion can persist well into the day; a weak one may break as sunshine warms the ground or wind increases.
How to read the inversion forecast
Possible timing describes when the model indicates a bounded cloud layer below the summit. Separate spells are listed separately. Times are approximate, not predictions of exactly when fog will form or clear. Cloud top estimates the upper boundary of that lower layer; higher cloud may still limit sunshine. “Unavailable” means the current height cannot be assessed. An earlier signal retained is a cautious watch based on a previous run or a neighbouring forecast date, not a newly confirmed inversion. Confidence bands describe limitations in the evidence, not measured probabilities.
Compare the forecast with cloud observations
Our Snowdon and Tryfan cloud-base observations use webcam views and terrain heights to estimate where cloud meets the slopes. Check the observation time and compare it with the forecast for that mountain.
Cloud base is the lower edge, not the cloud top. These observations alone cannot confirm an inversion or tell you that the summit is above the whole cloud layer. They are provisional, camera-facing estimates, with gaps when the view cannot be assessed.
What if the cloud top is close to the summit?
Cloud heights are uncertain. A summit near the estimated top can still be worth watching, even when the central forecast leaves it in cloud. We include borderline candidates with an estimated top up to 300 m above the summit, labelled low confidence. That allowance is provisional, not a measured error range. The summit may stay in cloud throughout.
A cloud base near the summit is not enough on its own: the layer could extend much higher. Valley-fog possibilities are listed separately when the weather favours early mist but its depth cannot be established. Consecutive dates describe recurring opportunities, not a promise of uninterrupted cloud below the hills.
What should you check?
- The forecast cloud top and the height of your intended summit.
- Wind speed at several elevations; stronger wind can mix the layers.
- Humidity, valley fog and observations from nearby high-level stations.
- Freezing conditions below the cloud, where paths and roads may be icy.
Plan for the cloud too.
The summit view is only part of the day. Navigation can be difficult in dense cloud below an inversion, and cold damp air can make lower slopes feel raw. Carry the kit and navigation skills for the least photogenic part of the route, not just the hoped-for view.