Rule
Fog Hunter
Cwm Idwal - Fog Hunter - Snowdonia (Eryri)
Bethesda, Wales, United Kingdom
Thick, moody fog for atmospheric forest and landscape shots
Currently
Real-time conditionsDewpoint Spread1.6°C
Visibility24135 (Clear)
Relative Humidity90%
Wind Speed5.4m/s (moderate winds)
Upcoming Opportunities
When all conditions match, PhotoWeather marks an opportunity window.
Times shown in Europe/London
Next opportunity
Moderate Fog
Cwm Idwal
Sun, Apr 12 · 22:00–01:00 · 3h window
Low confidence
19%
🌫️Fog Probability62.7%
Dewpoint Spread: 0.6°C
Visibility: 24135 (Clear)
Relative Humidity: 96%
Wind Speed: 2.0m/s (calm conditions)
Moderate Fog
Cwm Idwal
Mon, Apr 13 · 18:00–19:00
🌫️Fog Probability:69%
Low
Dense Fog at Sunset
Cwm Idwal
Mon, Apr 13 · 19:00–21:00
🌫️Fog Probability:83.5-88.6%
High
Dense Fog
Cwm Idwal
Mon, Apr 13 · 21:00–02:00
🌫️Fog Probability:86-100%
High
Moderate Fog
Cwm Idwal
Wed, Apr 15 · 16:00–17:00
🌫️Fog Probability:74.6%
Medium
Moderate Fog at Sunset
Cwm Idwal
Wed, Apr 15 · 20:00–21:00
🌫️Fog Probability:83.6%
Medium
Moderate Fog
Cwm Idwal
Wed, Apr 15 · 21:00–23:00
🌫️Fog Probability:79.3-83.6%
Medium
+3 more windows in the next 10 days
What this forecast looks for
Plain-language explanation from the ruleThis forecast tracks when valley inversions and mountain mist create atmospheric conditions for photography in Snowdonia's glacial valleys. We monitor temperature inversions, humidity patterns, and wind conditions to predict optimal fog photography opportunities.
Snowdonia's deep glacial valleys—Nant Gwynant, Llanberis Pass, and Ogwen Valley—act as natural fog bowls where cold air settles overnight, creating spectacular valley inversions with mountain peaks rising through cloud seas. The region's high rainfall and numerous lakes add moisture to the atmosphere, producing frequent mist conditions that transform slate landscapes and mountain tarns into ethereal scenes.
What makes Snowdonia fog photography distinctive:
- Valley inversions - Nant Gwynant and Ogwen Valley trap cold air, creating cloud seas with peaks emerging above
- Lake mist - Llyn Padarn and Llyn Ogwen generate morning mist that drifts across mirror-still water
- Slate atmosphere - Historic slate quarries at Llanberis create moody industrial landscapes in fog
- Glacial cwms - Cwm Idwal's enclosed cirque traps mist, creating atmospheric waterfall scenes at Devil's Kitchen
The most reliable fog conditions occur during settled high-pressure periods in autumn and winter (September-February) when clear skies allow overnight cooling to create temperature inversions. Nant Gwynant valley is particularly prone to inversions—position yourself at higher viewpoints like Pen-y-Gwryd or along the A498 to capture peaks rising through cloud. Llyn Padarn generates morning mist that drifts past Dolbadarn Castle's tower, creating atmospheric castle scenes. Cwm Idwal's enclosed glacial bowl traps mist against the dramatic headwall of Devil's Kitchen. The timing is critical—arrive before dawn as mist typically burns off within an hour or two of sunrise. Wales's wet climate means fog is common, but our forecast identifies the photogenic conditions when visibility is just right—not too thick to lose definition, not too thin to lack atmosphere.
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72-hour requirements breakdown
What passed or failed, hour by hour0matching hours in the next 95 hours
AND logic: all conditions required
Meets requirement
Misses requirement
Time Europe/London | Fog Probability ≥ 60.0% |
|---|---|
| Wed, Apr 8 | |
| 02:00 | 0% |
| 03:00 | 0% |
| 04:00 | 0% |
| 05:00 | 0% |
| 06:00 | 0% |
| 07:00 | 0% |
| 08:00 | 0% |
| 09:00 | 0% |
| 10:00 | 0% |
| 11:00 | 0% |
| 12:00 | 0% |
| 13:00 | 0% |
| 14:00 | 0% |
| 15:00 | 0% |
| 16:00 | 0% |
| 17:00 | 0% |
| 18:00 | 0% |
| 19:00 | 0% |
| 20:00 | 0% |
| 21:00 | 0% |
| 22:00 | 0% |
| 23:00 | 0% |
| Thu, Apr 9 | |
| 24:00 | 27% |
| 01:00 | 0% |
| 02:00 | 0% |
| 03:00 | 0% |
| 04:00 | 0% |
| 05:00 | 0% |
| 06:00 | 0% |
| 07:00 | 0% |
| 08:00 | 0% |
| 09:00 | 0% |
| 10:00 | 0% |
| 11:00 | 0% |
| 12:00 | 0% |
| 13:00 | 0% |
| 14:00 | 0% |
| 15:00 | 0% |
| 16:00 | 0% |
| 17:00 | 0% |
| 18:00 | 0% |
| 19:00 | 0% |
| 20:00 | 0% |
| 21:00 | 0% |
| 22:00 | 0% |
| 23:00 | 0% |
| Fri, Apr 10 | |
| 24:00 | 0% |
| 01:00 | 0% |
| 02:00 | 0% |
| 03:00 | 0% |
| 04:00 | 0% |
| 05:00 | 0% |
| 06:00 | 0% |
| 07:00 | 0% |
| 08:00 | 0% |
| 09:00 | 0% |
| 10:00 | 0% |
| 11:00 | 0% |
| 12:00 | 0% |
| 13:00 | 0% |
| 14:00 | 0% |
| 15:00 | 0% |
| 16:00 | 0% |
| 17:00 | 0% |
| 18:00 | 0% |
| 19:00 | 0% |
| 20:00 | 0% |
| 21:00 | 0% |
| 22:00 | 0% |
| 23:00 | 0% |
| Sat, Apr 11 | |
| 24:00 | 0% |
| 01:00 | 0% |
| 02:00 | 0% |
| 03:00 | 0% |
| 04:00 | 0% |
| 05:00 | 0% |
| 06:00 | 0% |
| 07:00 | 0% |
| 08:00 | 0% |
| 09:00 | 0% |
| 10:00 | 0% |
| 11:00 | 0% |
| 12:00 | 0% |
| 13:00 | 0% |
| 14:00 | 0% |
| 15:00 | 0% |
| 16:00 | 0% |
| 17:00 | 0% |
| 18:00 | 0% |
| 19:00 | 0% |
| 20:00 | 0% |
| 21:00 | 0% |
| 22:00 | 0% |
| 23:00 | 0% |
| Sun, Apr 12 | |
| 24:00 | 0% |
How to read: colored cells show whether each predicate requirement is met; highlighted rows mean the full rule matched (an opportunity).
What does Fog Probability mean?
Inputs that drive the scoreThis derived score summarizes multiple raw weather signals. The table below shows the supporting inputs hour by hour, so you can see what's pushing the score up or down.
| Time Europe/London | Clear Sky Probability (Ensemble) % | Dew Point °C | Rainfall mm | Relative Humidity % | Snowfall cm | Solar Elevation ° | Temperature °C | Total Precipitation mm | Vapor Pressure Deficit kPa | Visibility m | Wind Gusts m/s | Wind Speed m/s |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Thu, Apr 9
Sunrise 06:31
Sunset 20:05 | ||||||||||||
| 03:00 ☾ | 0% | 7.4°C | 0mm | 90% | 0cm | -26° | 9°C | 0mm | 0.12kPa | 24135m | 7.9m/s | 5.4m/s |
| 04:00 ☾ | 0% | 6.1°C | 0mm | 86% | 0cm | -20° | 8.3°C | 0mm | 0.15kPa | 24135m | 9m/s | 5.6m/s |
| 05:00 ☾ | 0% | 5.2°C | 0mm | 84% | 0cm | -13° | 7.8°C | 0mm | 0.17kPa | 24135m | 11m/s | 6.8m/s |
| 06:00 ☾ | 0% | 5.4°C | 0mm | 86% | 0cm | -5.2° | 7.7°C | 0mm | 0.15kPa | 24134m | 13m/s | 8m/s |
| 07:00 | 0% | 6.2°C | 0mm | 90% | 0cm | 3.6° | 7.8°C | 0mm | 0.11kPa | 5882m | 14m/s | 8.3m/s |
| 08:00 | 0% | 6.7°C | 0.28mm | 90% | 0cm | 12° | 8.3°C | 0mm | 0.11kPa | 21608m | 12m/s | 7.2m/s |
| 09:00 | 0% | 7.4°C | 0.74mm | 94% | 0cm | 21° | 8.3°C | 1mm | 0.07kPa | 1028m | 7.8m/s | 4.6m/s |
| 10:00 | 0% | 7.8°C | 0.55mm | 95% | 0cm | 30° | 8.5°C | 1.7mm | 0.06kPa | 1506m | 10m/s | 5.4m/s |
| 11:00 | 0% | 6.2°C | 0mm | 86% | 0cm | 37° | 8.4°C | 1.9mm | 0.16kPa | 24135m | 11m/s | 8.1m/s |
| 12:00 | 0% | 4.7°C | 0mm | 78% | 0cm | 42° | 8.3°C | 2mm | 0.24kPa | 23736m | 12m/s | 8.8m/s |
| 13:00 | 0% | 4.5°C | 0mm | 81% | 0cm | 44° | 7.5°C | 2.2mm | 0.19kPa | 24135m | 12m/s | 9.3m/s |
| 14:00 | 0% | 3.3°C | 0mm | 76% | 0cm | 44° | 7.3°C | 0mm | 0.25kPa | 24135m | 11m/s | 8.5m/s |
| 15:00 | 0% | 2.8°C | 0.01mm | 71% | 0cm | 40° | 7.7°C | 0.19mm | 0.31kPa | 7600m | 11m/s | 9.3m/s |
| 16:00 | 0% | 2.6°C | 0mm | 71% | 0cm | 34° | 7.5°C | 0.44mm | 0.3kPa | 20001m | 11m/s | 9m/s |
| 17:00 | 0% | 1.9°C | 0mm | 69% | 0cm | 26° | 7.2°C | 0.56mm | 0.32kPa | 24134m | 12m/s | 9.1m/s |
| 18:00 | 1% | 1.9°C | 0mm | 71% | 0cm | 18° | 6.9°C | 0.75mm | 0.29kPa | 24134m | 12m/s | 8.7m/s |
| 19:00 | 1% | 1.6°C | 0mm | 71% | 0cm | 9° | 6.4°C | 0.81mm | 0.28kPa | 24135m | 12m/s | 8.9m/s |
| 20:00 | 16% | 1.2°C | 0mm | 72% | 0cm | 0.47° | 5.9°C | 0mm | 0.26kPa | 24135m | 11m/s | 7.1m/s |
| 21:00 ☾ | 32% | 1°C | 0mm | 73% | 0cm | -8.4° | 5.5°C | 0mm | 0.24kPa | 24134m | 10m/s | 6.5m/s |
| 22:00 ☾ | 47% | 0.9°C | 0mm | 73% | 0cm | -16° | 5.3°C | 0.06mm | 0.24kPa | 24006m | 10m/s | 6.6m/s |
| 23:00 ☾ | 42% | 0.7°C | 0mm | 74% | 0cm | -22° | 5°C | 0.13mm | 0.23kPa | 24135m | 10m/s | 6.7m/s |
| Fri, Apr 10
Sunrise 06:31
Sunset 20:05 | ||||||||||||
| 24:00 ☾ | 37% | 0.4°C | 0mm | 74% | 0cm | -27° | 4.6°C | 0.13mm | 0.22kPa | 24134m | 9.2m/s | 5.8m/s |
| 01:00 ☾ | 32% | 0.4°C | 0mm | 76% | 0cm | -29° | 4.3°C | 0.19mm | 0.2kPa | 24135m | 9.1m/s | 5.5m/s |
| 02:00 ☾ | 24% | 0.1°C | 0mm | 75% | 0cm | -28° | 4.2°C | 0mm | 0.2kPa | 24134m | 7.6m/s | 4.1m/s |
| 03:00 ☾ | 15% | -0.2°C | 0mm | 74% | 0cm | -25° | 3.9°C | 0mm | 0.21kPa | 24134m | 7.3m/s | 3.9m/s |
| 04:00 ☾ | 7% | -0.6°C | 0mm | 72% | 0cm | -20° | 3.9°C | 0mm | 0.22kPa | 24135m | 4.8m/s | 3.2m/s |
| 05:00 ☾ | 5% | -0.8°C | 0mm | 71% | 0cm | -13° | 3.8°C | 0mm | 0.23kPa | 24134m | 4.1m/s | 3.2m/s |
| 06:00 ☾ | 2% | -1.2°C | 0mm | 70% | 0cm | -4.9° | 3.9°C | 0mm | 0.24kPa | 24134m | 3.1m/s | 2.7m/s |
| 07:00 | 0% | -1.1°C | 0mm | 68% | 0cm | 3.9° | 4.2°C | 0mm | 0.26kPa | 24135m | 3.2m/s | 2.8m/s |
| 08:00 | 0% | -0.9°C | 0mm | 68% | 0cm | 13° | 4.5°C | 0mm | 0.27kPa | 24134m | 3.1m/s | 2.6m/s |
| 09:00 | 0% | -0.8°C | 0mm | 65% | 0cm | 22° | 5.1°C | 0mm | 0.31kPa | 24134m | 3.5m/s | 3m/s |
| 10:00 | 0% | -1.5°C | 0mm | 61% | 0cm | 30° | 5.5°C | 0mm | 0.35kPa | 24135m | 3.3m/s | 2.5m/s |
| 11:00 | 0% | -2°C | 0mm | 56% | 0cm | 37° | 6°C | 0mm | 0.41kPa | 24135m | 3.7m/s | 2.6m/s |
| 12:00 | 0% | -2°C | 0mm | 54% | 0cm | 42° | 6.5°C | 0mm | 0.44kPa | 24134m | 4.9m/s | 3.4m/s |
| 13:00 | 0% | -1.7°C | 0mm | 55% | 0cm | 45° | 6.7°C | 0mm | 0.44kPa | 24134m | 6.1m/s | 4.1m/s |
| 14:00 | 0% | -0.8°C | 0mm | 58% | 0cm | 44° | 6.9°C | 0mm | 0.41kPa | 24134m | 7m/s | 4.6m/s |
| 15:00 | 0% | 0.1°C | 0.01mm | 63% | 0cm | 40° | 6.7°C | 0mm | 0.37kPa | 24134m | 7.3m/s | 4.7m/s |
| 16:00 | 0% | 1.3°C | 0mm | 70% | 0cm | 34° | 6.4°C | 0mm | 0.29kPa | 24134m | 7.4m/s | 4.5m/s |
| 17:00 | 0% | 2.1°C | 0mm | 75% | 0cm | 27° | 6.2°C | 0.06mm | 0.24kPa | 24134m | 6.6m/s | 4m/s |
| 18:00 | 0% | 2.6°C | 0.02mm | 79% | 0cm | 18° | 6°C | 0.06mm | 0.2kPa | 24135m | 6.4m/s | 4.1m/s |
| 19:00 | 0% | 2.9°C | 0.02mm | 82% | 0cm | 9.2° | 5.7°C | 0.13mm | 0.16kPa | 13019m | 7.4m/s | 4.5m/s |
| 20:00 | 0% | 3.1°C | 0.09mm | 86% | 0cm | 0.69° | 5.4°C | 0mm | 0.13kPa | 24135m | 11m/s | 5m/s |
| 21:00 ☾ | 0% | 3.4°C | 0.08mm | 87% | 0cm | -8.2° | 5.4°C | 0.19mm | 0.12kPa | 24134m | 12m/s | 5.4m/s |
| 22:00 ☾ | 0% | 2.8°C | 0.62mm | 82% | 0cm | -16° | 5.7°C | 0.44mm | 0.17kPa | 13734m | 15m/s | 6.1m/s |
| 23:00 ☾ | 0% | 3°C | 0.13mm | 84% | 0cm | -22° | 5.5°C | 0.81mm | 0.15kPa | 24134m | 16m/s | 6.8m/s |
| Sat, Apr 11
Sunrise 06:29
Sunset 20:07 | ||||||||||||
| 24:00 ☾ | 0% | 3.8°C | 0.6mm | 82% | 0cm | -26° | 6.6°C | 1.2mm | 0.17kPa | 14403m | 17m/s | 7m/s |
| 01:00 ☾ | 0% | 4.8°C | 1.7mm | 84% | 0cm | -28° | 7.4°C | 2.9mm | 0.17kPa | 7849m | 19m/s | 8.7m/s |
| 02:00 ☾ | 0% | 5.5°C | 3.5mm | 89% | 0cm | -28° | 7.2°C | 1.9mm | 0.11kPa | 4483m | 14m/s | 9m/s |
| 03:00 ☾ | 0% | 3.3°C | 0.67mm | 90% | 0cm | -25° | 4.8°C | 3.4mm | 0.09kPa | 1933m | 17m/s | 8m/s |
| 04:00 ☾ | 0% | 2.4°C | 0mm | 76% | 0cm | -20° | 6.4°C | 3.8mm | 0.23kPa | 24135m | 16m/s | 9.5m/s |
| 05:00 ☾ | 0% | 1.1°C | 0mm | 74% | 0cm | -13° | 5.4°C | 3.8mm | 0.23kPa | 24135m | 17m/s | 9.9m/s |
| 06:00 ☾ | 0% | 1.7°C | 0mm | 78% | 0cm | -4.5° | 5.1°C | 3.8mm | 0.19kPa | 24135m | 16m/s | 11m/s |
| 07:00 | 0% | 1°C | 0mm | 77% | 0cm | 4.3° | 4.7°C | 3.8mm | 0.19kPa | 24135m | 14m/s | 10m/s |
| 08:00 | 2% | 1°C | 0mm | 76% | 0cm | 13° | 4.9°C | 2.7mm | 0.2kPa | 17284m | 14m/s | 9.4m/s |
| 09:00 | 5% | 1°C | 0mm | 75% | 0cm | 22° | 5°C | 1.5mm | 0.21kPa | 10433m | 15m/s | 8.7m/s |
| 10:00 | 7% | 1°C | 0mm | 74% | 0cm | 30° | 5.2°C | 0.38mm | 0.23kPa | 3582m | 16m/s | 8m/s |
| 11:00 | 8% | 1.4°C | 0.03mm | 79% | 0cm | 37° | 4.8°C | 0.71mm | 0.18kPa | 10106m | 17m/s | 9.2m/s |
| 12:00 | 8% | 1.8°C | 0.06mm | 83% | 0cm | 43° | 4.4°C | 1mm | 0.14kPa | 16629m | 18m/s | 10m/s |
| 13:00 | 9% | 2.1°C | 0.09mm | 87% | 0cm | 45° | 4°C | 1.4mm | 0.1kPa | 23153m | 19m/s | 12m/s |
| 14:00 | 19% | 2.6°C | 0.07mm | 89% | 0cm | 44° | 4.2°C | 1.1mm | 0.09kPa | 18326m | 19m/s | 12m/s |
| 15:00 | 29% | 3.2°C | 0.05mm | 91% | 0cm | 41° | 4.5°C | 0.79mm | 0.07kPa | 13500m | 18m/s | 12m/s |
| 16:00 | 39% | 3.7°C | 0.03mm | 93% | 0cm | 35° | 4.7°C | 0.5mm | 0.06kPa | 8673m | 18m/s | 12m/s |
| 17:00 | 36% | 3.9°C | 0.03mm | 94% | 0cm | 27° | 4.8°C | 0.79mm | 0.05kPa | 7203m | 18m/s | 12m/s |
| 18:00 | 34% | 4°C | 0.04mm | 94% | 0cm | 18° | 4.8°C | 1.1mm | 0.05kPa | 5732m | 18m/s | 12m/s |
| 19:00 | 31% | 4.1°C | 0.04mm | 95% | 0cm | 9.5° | 4.9°C | 1.4mm | 0.05kPa | 4261m | 17m/s | 12m/s |
| 20:00 | 31% | 3.9°C | 0.21mm | 94% | 0cm | 0.92° | 4.8°C | 1.3mm | 0.05kPa | 5793m | 16m/s | 11m/s |
| 21:00 ☾ | 31% | 3.8°C | 0.39mm | 94% | 0cm | -7.9° | 4.6°C | 1.3mm | 0.05kPa | 7324m | 16m/s | 9.9m/s |
| 22:00 ☾ | 31% | 3.6°C | 0.56mm | 94% | 0cm | -15° | 4.5°C | 1.2mm | 0.05kPa | 8856m | 15m/s | 9m/s |
| 23:00 ☾ | 28% | 3.7°C | 0.54mm | 94% | 0cm | -22° | 4.5°C | 2.4mm | 0.05kPa | 8942m | 14m/s | 8.3m/s |
| Sun, Apr 12
Sunrise 06:26
Sunset 20:08 | ||||||||||||
| 24:00 ☾ | 24% | 3.8°C | 0.53mm | 95% | 0cm | -26° | 4.6°C | 3.7mm | 0.05kPa | 9028m | 13m/s | 7.5m/s |
| 01:00 ☾ | 21% | 3.9°C | 0.51mm | 95% | 0cm | -28° | 4.6°C | 4.9mm | 0.04kPa | 9114m | 11m/s | 6.7m/s |
| 02:00 ☾ | 22% | 3.8°C | 0.4mm | 94% | 0cm | -28° | 4.6°C | 3.8mm | 0.05kPa | 8636m | 12m/s | 7.4m/s |
How to read: these inputs help produce the derived score; they are not requirements by themselves.
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