Find the inversion lid
The temperature profile should show warmer air above colder, moist air lower down. A clear lid helps trap the valley cloud beneath the higher slopes.
Eryri / Snowdonia & North Wales
Yr Wyddfa (Snowdon) cloud inversion forecast. Next 24 hours.
See the next 24 hours around Yr Wyddfa, with a focused Eryri map, the strongest dawn window and the wider mountain signal around the summit.
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Local outlook
Yr Wyddfa (Snowdon) over the next 24 hours
Very likely
Likely
Possible
Purple dot: Yr Wyddfa (Snowdon)
Latest regional signal
Unlikely
Best window
No clear viewing window yet
Captured 5 Sep, 11:04 BST · model rating, not a literal probability
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See the next two days
The public map stays focused on the next 24 hours. Premium extends the detailed inversion map, atmospheric profile and forecast window to around two days, often longer.
Local inversion guide
When can you see a cloud inversion at Yr Wyddfa?
The best chance comes when colder, moist air settles on low ground beneath warmer, drier air, winds stay light and the cloud top remains below your viewpoint.
Yr Wyddfa rises above several deep approaches, including Rhyd Ddu, Nant Gwynant and Llanberis. Low cloud can fill one valley while another side of the mountain stays open.
A regional Eryri signal does not guarantee a clear summit. Look for a cloud top comfortably below the mountain, a strong moisture contrast at the top of the layer and dry air above it.
Before you travel: the map shows the wider pattern across Eryri / Snowdonia & North Wales, not a promise for one summit. Check the latest wind, visibility and mountain forecast for your exact route.
See the forecast data and limitationsCompare more than one side
Rhyd Ddu, Nant Gwynant and Llanberis can behave differently. Agreement across nearby forecast points is stronger evidence than fog in only one approach.
Leave clear air above
A useful cloud sea needs its top well below Yr Wyddfa with drier air above. Thick hill cloud can hide the summit even when lower valleys are foggy.
Watch the calmest hours
Light wind helps a cloud pool survive. The strongest window is often near dawn, but exposed summit conditions can still be very different from the valleys.
Quick answers
Cloud inversion questions for Yr Wyddfa (Snowdon)
Are Snowdon and Yr Wyddfa the same forecast here?
Yes. Yr Wyddfa is the Welsh name prioritised by Eryri National Park, and Snowdon is included so people using either name reach the same canonical forecast page.
Can one side of Yr Wyddfa be foggy while another stays clear?
Yes. Eryri's terrain is complex, so valley cloud can vary around Rhyd Ddu, Nant Gwynant and Llanberis. The map helps show whether the wider regional signal agrees.
Does a Likely signal mean the mountain is safe to climb?
No. It is a cloud-inversion signal, not a route or safety recommendation. Yr Wyddfa is a serious mountain; check the full weather forecast, route conditions and official safety advice.
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