Cefn yr Ystrad weather forecast.

Cloud-free timing: Cloudy early, clearing later.

A mixed day on Cefn yr Ystrad: summit wind broadly 15-30 mph, with gusts 30-40 mph early in the morning (strong winds). Much calmer lower down - generally 5-15 mph in the valley, rising towards the tops. Cloud base around 500–800 m in the morning, lifting to 1600–1900 m around midday and 1900–2200 m by late afternoon. Summit cloud should lift later, bringing a better chance of clear views. Little or no rain expected. Confidence moderate (forecast models agree on the walking impact of the wind) - the summit peak could reasonably be 24-26 mph, so treat the headline as mid-range.

Forecast confidence: Thunderstorm timing is inherently uncertain and may shift by several hours.

Cloud-free timing: Cloudy early, clearing later.

A mixed day on Cefn yr Ystrad: summit wind broadly 5-15 mph, with gusts 10-20 mph around midday (a moderate breeze). Thunderstorms are a significant hazard from the morning into the afternoon. Exposed summits and ridges are a poor choice while storms are nearby. Cloud base around 400–700 m in the morning, lifting to 1000–1300 m around midday and 1700–2000 m by late afternoon. Summit cloud should lift later, bringing a better chance of clear views. Little or no rain expected.

Forecast confidence: Thunderstorm timing is inherently uncertain and may shift by several hours.

Cloud-free timing: Around 0% early, improving to around 80% later.

A rough, clagged-in day on Cefn yr Ystrad: summit wind broadly 15-30 mph, with gusts 30-40 mph during the evening (strong winds). Thunderstorms are forecast from early morning into the evening. Avoid exposed summits and ridges during the risk period. There could be a spate risk based on forecast rainfall. Burns and unbridged crossings may rise quickly. Most likely from around 04:00 until around 20:00. Much calmer lower down - generally 5-15 mph in the valley, rising towards the tops. Cloud base around 400–700 m through the morning, lifting to 800–1100 m by late afternoon. The top is likely to drift in and out of cloud, with the best chance of a view from late afternoon into the evening. Cloud is likely to hang lowest on southern slopes; the northern side should see somewhat higher bases and better breaks. A persistently wet day is possible, with around 10-20 mm indicated; local totals could vary considerably. Confidence moderate (forecast models agree on the walking impact of the wind) - the summit peak could reasonably be 23-30 mph, so treat the headline as mid-range.

Forecast confidence: Thunderstorm timing is inherently uncertain and may shift by several hours.

Cloud-free timing: Around 0% early, improving to around 60% later.

A rough, clagged-in day on Cefn yr Ystrad: summit wind broadly 15-30 mph, with gusts 35-45 mph early in the morning (strong winds). A meaningful thunderstorm risk is indicated from the morning into the evening. Avoid committing to exposed ridges if storms begin to build. The ground is likely to be wet after recent rain. There could be a spate risk based on forecast rainfall. Burns and unbridged crossings may rise quickly. Most likely from around 05:00 until around 20:00. Much calmer lower down - generally 5-15 mph in the valley, rising towards the tops. Cloud base around 400–700 m through the morning, lifting to 700–1000 m by late afternoon. The top is likely to drift in and out of cloud, with the best chance of a view from late afternoon into the evening. Cloud is likely to hang lowest on western slopes; the eastern side should see somewhat higher bases and better breaks. A persistently wet day is possible, with around 10-20 mm indicated; local totals could vary considerably. Confidence moderate (forecast models agree on the walking impact of the wind) - the summit peak could reasonably be 24-32 mph, so treat the headline as mid-range. Cloud base is the least certain part of this - the models are only moderately agreed, so it could sit a couple of hundred metres either way.

Forecast confidence: Thunderstorm timing is inherently uncertain and may shift by several hours.

Cloud-free timing: Around 0% early, improving to around 80% later.

A wild day on Cefn yr Ystrad: summit wind broadly 10-25 mph, with gusts 25-35 mph around midday (fresh and blowy). Thunderstorms are a significant hazard from the morning into the evening. Exposed summits and ridges are a poor choice while storms are nearby. The ground is likely to be wet after recent rain. There could be a spate risk based on forecast rainfall. Burns and unbridged crossings may rise quickly. Most likely from around 08:00 until around 23:00. Cloud base around 400–700 m through the morning, lifting to 600–900 m by late afternoon. The top is likely to drift in and out of cloud, with the best chance of a view from late afternoon into the evening. Cloud is likely to hang lowest on southwestern slopes; the northeastern side should see somewhat higher bases and better breaks. A persistently wet day is possible, with around 10-20 mm indicated; local totals could vary considerably. Confidence moderate (forecast models agree on the walking impact of the wind) - the summit peak could reasonably be 15-27 mph, so treat the headline as mid-range.

Forecast confidence: Thunderstorm timing is inherently uncertain and may shift by several hours.

Cloud-free timing: Around 33% early, improving to around 60% later.

A mixed day on Cefn yr Ystrad: summit wind broadly 15-30 mph, with gusts 30-40 mph during the evening (strong winds). A meaningful thunderstorm risk is indicated from early morning into the evening. Avoid committing to exposed ridges if storms begin to build. The ground is likely to be wet after recent rain. There could be a spate risk based on forecast rainfall. Burns and unbridged crossings may rise quickly. Most likely from around 17:00 until around 03:00 the following day. Much calmer lower down - generally 5-15 mph in the valley, rising towards the tops. Cloud base around 400–700 m in the morning, lifting to 900–1200 m around midday and 1300–1600 m by late afternoon. The top is likely to drift in and out of cloud; views may come and go. Cloud is likely to hang lowest on southwestern slopes; the northeastern side should see somewhat higher bases and better breaks. Some rain is likely, with around 5-10 mm indicated; timing and local totals remain uncertain. Confidence moderate (forecast models agree on the walking impact of the wind) - the summit peak could reasonably be 23-29 mph, so treat the headline as mid-range.

Forecast confidence: Forecast models disagree on whether meaningful rain reaches the hills during 10:00-16:00.

Cloud-free timing: Cloudy early, clearing later.

A mixed day on Cefn yr Ystrad: summit wind broadly 20-35 mph, with gusts 35-45 mph around midday (gale-force winds). The ground is likely to be wet after recent rain. Cloud is likely to hang lowest on western slopes; the eastern side should see somewhat higher bases and better breaks. Some rain is likely, with up to around 2 mm indicated; timing and local totals remain uncertain. Confidence moderate (forecast models agree on the walking impact of the wind) - the summit peak could reasonably be 22-34 mph, so treat the headline as mid-range.