Mountain Weather

Mountain inversion forecast.

Current cloud-sea candidates, how inversions form and why the view from the summit can be very different from the glen.

Live model signal

Upcoming inversion candidates.

These peaks may stand above a bounded layer of valley cloud. They are possibilities, not promises—confidence and cloud height matter.

Forecast run Tuesday 25 August 2026

Arkle

Low confidence
Best chanceEarly morningPossible cloud top484 mSummit clearance303 m

An outside chance of a cloud sea early in the morning, below the summit, with a possible top in 400-700 m, but the cloud could just as easily sit over the top.

Cùl Beag

Low confidence
Best chanceEarly morningPossible cloud top631 mSummit clearance138 m

An outside chance of a cloud sea early in the morning, below the summit, with a possible top in 600-900 m, but the cloud could just as easily sit over the top.

Cùl Mòr

Low confidence
Best chanceEarly morningPossible cloud top631 mSummit clearance218 m

An outside chance of a cloud sea early in the morning, below the summit, with a possible top in 600-900 m, but the cloud could just as easily sit over the top.

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.

A sunlit Scottish ridge emerging above a cloud inversion
A clear summit can sit only a few hundred metres above a cold, cloudy glen.

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

Best chance describes the broad part of the day when the model keeps a bounded cloud layer below the summit. It is a planning window, not an appointment: the layer may form or break earlier than shown. The possible cloud top estimates the upper boundary of the modelled valley cloud. Summit clearance is the vertical gap between that cloud top and the mountain summit. A larger positive clearance is encouraging, but low confidence means the cloud could still sit over the top. An “earlier signal retained” label means a useful signal from a previous forecast run has weakened or disappeared in the latest run; it is kept as a low-confidence possibility when the wider weather pattern still supports it.

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.