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Rule Fog Hunter

Pen yr Ole Wen - Fog Hunter - Snowdonia (Eryri)

Bethesda, Wales, United Kingdom

Thick, moody fog for atmospheric forest and landscape shots

Currently

Real-time conditions
Fog Probability
0%
Dewpoint Spread6.2°C
Visibility24134 (Clear)
Relative Humidity66%
Wind Speed7.6m/s (moderate winds)

Upcoming Opportunities

When all conditions match, PhotoWeather marks an opportunity window.

Times shown in Europe/London
fog weather icon
Next opportunity
Dense Fog
Pen yr Ole Wen
Fri, Jun 12 · 16:00–20:00 · 4h window
Low confidence
32%
🌫️Fog Probability77.9-95.3%
Dewpoint Spread: 0.1°C
Visibility: 571 (Fog)
Relative Humidity: 99%
Wind Speed: 2.2m/s (calm conditions)
fog weather icon
Dense Fog at Sunset
Pen yr Ole Wen
Fri, Jun 12 · 20:00–23:00
🌫️Fog Probability:88.6%
Medium

What this forecast looks for

Plain-language explanation from the rule

This 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 hour
0matching hours in the next 95 hours
AND logic: all conditions required
Meets requirement
Misses requirement
Time
Europe/London
Fog Probability
≥ 75.0%
Sun, Jun 7
15:000%
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Mon, Jun 8
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Tue, Jun 9
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Wed, Jun 10
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Thu, Jun 11
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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 score

This 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
Mon, Jun 8 Sunrise 04:51 Sunset 21:39
16:00
98% 6.1°C 0mm 66% 0cm 47° 12°C 0mm 0.48kPa 24134m 9m/s 7.6m/s
17:00
91% 6.8°C 0mm 70% 0cm 38° 12°C 0mm 0.43kPa 24135m 9.9m/s 8.2m/s
18:00
85% 7.4°C 0mm 73% 0cm 29° 12°C 0.06mm 0.37kPa 24135m 10m/s 8.5m/s
19:00
78% 7.5°C 0mm 76% 0cm 20° 12°C 0.06mm 0.33kPa 23922m 11m/s 7.8m/s
20:00
54% 7.7°C 0mm 79% 0cm 12° 11°C 0.06mm 0.28kPa 23605m 11m/s 6.3m/s
21:00
30% 7.7°C 0mm 81% 0cm 4.1° 11°C 0.19mm 0.25kPa 24086m 10m/s 5.6m/s
22:00 ☾
6% 7.5°C 0mm 80% 0cm -2.9° 11°C 0.31mm 0.26kPa 24135m 10m/s 5.6m/s
23:00 ☾
4% 7.3°C 0mm 78% 0cm -8.4° 11°C 0.56mm 0.29kPa 24134m 11m/s 5.9m/s
Tue, Jun 9 Sunrise 04:51 Sunset 21:39
24:00 ☾
2% 7°C 0mm 78% 0cm -12° 11°C 0.63mm 0.28kPa 24135m 12m/s 7m/s
01:00 ☾
0% 6.9°C 0mm 83% 0cm -14° 9.6°C 0.63mm 0.2kPa 24135m 11m/s 5.9m/s
02:00 ☾
1% 6.9°C 0mm 84% 0cm -13° 9.4°C 0.06mm 0.19kPa 24135m 11m/s 6.1m/s
03:00 ☾
1% 7.4°C 0mm 85% 0cm -11° 9.8°C 0.25mm 0.18kPa 20273m 10m/s 6.9m/s
04:00 ☾
2% 7.1°C 0mm 88% 0cm -5.9° 9°C 0.38mm 0.14kPa 24135m 10m/s 6.5m/s
05:00
1% 6.9°C 0mm 89% 0cm 0.7° 8.6°C 0.5mm 0.13kPa 22630m 10m/s 5.9m/s
06:00
1% 6.9°C 0mm 88% 0cm 7.8° 8.8°C 0.63mm 0.14kPa 24135m 10m/s 6.5m/s
07:00
0% 6.8°C 0mm 85% 0cm 16° 9.1°C 0.63mm 0.17kPa 24135m 10m/s 7.1m/s
08:00
10% 7°C 0mm 84% 0cm 25° 9.5°C 0.13mm 0.18kPa 23374m 11m/s 7.9m/s
09:00
20% 7.2°C 0mm 84% 0cm 34° 9.7°C 0.25mm 0.19kPa 24134m 11m/s 9.1m/s
10:00
30% 7°C 0mm 82% 0cm 42° 9.9°C 0.38mm 0.22kPa 24135m 11m/s 9.2m/s
11:00
26% 6.9°C 0mm 79% 0cm 50° 10°C 0.5mm 0.26kPa 24135m 11m/s 9.6m/s
12:00
23% 7°C 0mm 77% 0cm 57° 11°C 0.69mm 0.3kPa 23944m 12m/s 9.7m/s
13:00
19% 6.8°C 0mm 74% 0cm 60° 11°C 0.88mm 0.34kPa 24040m 12m/s 10m/s
14:00
31% 6.4°C 0mm 71% 0cm 59° 12°C 0.13mm 0.4kPa 24073m 13m/s 10m/s
15:00
44% 6.3°C 0mm 68% 0cm 54° 12°C 0.25mm 0.46kPa 24135m 12m/s 9.9m/s
16:00
56% 6.4°C 0mm 67% 0cm 47° 12°C 0.38mm 0.47kPa 24134m 12m/s 9.6m/s
17:00
56% 6.5°C 0mm 66% 0cm 38° 13°C 0.5mm 0.49kPa 24135m 11m/s 8.4m/s
18:00
56% 7.3°C 0mm 70% 0cm 29° 13°C 0.63mm 0.43kPa 23938m 11m/s 7.5m/s
19:00
56% 7.6°C 0mm 73% 0cm 21° 12°C 0.88mm 0.38kPa 24004m 10m/s 7m/s
20:00
46% 7.5°C 0mm 77% 0cm 12° 11°C 0.19mm 0.31kPa 20201m 10m/s 6m/s
21:00
35% 7.2°C 0mm 79% 0cm 4.2° 11°C 0.44mm 0.27kPa 21449m 9.8m/s 4.9m/s
22:00 ☾
25% 6.6°C 0mm 80% 0cm -2.8° 9.9°C 0.5mm 0.25kPa 23722m 9.3m/s 4.7m/s
23:00 ☾
19% 6.7°C 0mm 82% 0cm -8.3° 9.7°C 0.56mm 0.22kPa 24134m 9.1m/s 4.7m/s
Wed, Jun 10 Sunrise 04:50 Sunset 21:40
24:00 ☾
12% 6.6°C 0.02mm 81% 0cm -12° 9.7°C 0.69mm 0.23kPa 23701m 8.9m/s 4.5m/s
01:00 ☾
6% 6.9°C 0.24mm 83% 0cm -14° 9.7°C 1mm 0.21kPa 12432m 7.8m/s 4.2m/s
02:00 ☾
4% 6.6°C 0mm 82% 0cm -13° 9.6°C 0.19mm 0.22kPa 24134m 4.8m/s 2.8m/s
03:00 ☾
3% 6.2°C 0mm 82% 0cm -10° 9.2°C 0.31mm 0.22kPa 24134m 5.5m/s 3.4m/s
04:00 ☾
1% 5.9°C 0mm 85% 0cm -5.8° 8.3°C 0.5mm 0.17kPa 23444m 6.1m/s 4m/s
05:00
1% 6.2°C 0mm 88% 0cm 0.74° 8°C 0.63mm 0.12kPa 24134m 9.4m/s 5.1m/s
06:00
0% 6.3°C 0mm 87% 0cm 7.8° 8.3°C 0.69mm 0.14kPa 24134m 8.9m/s 4.8m/s
07:00
0% 7°C 0.01mm 88% 0cm 16° 9°C 0.88mm 0.14kPa 22902m 9m/s 5.3m/s
08:00
2% 6.9°C 0mm 81% 0cm 25° 10°C 0.13mm 0.23kPa 23278m 8.2m/s 5.8m/s
09:00
3% 7.1°C 0mm 81% 0cm 34° 10°C 0.38mm 0.24kPa 23472m 9.4m/s 7m/s
10:00
5% 6.7°C 0mm 76% 0cm 43° 11°C 0.5mm 0.3kPa 23738m 8.8m/s 7m/s
11:00
4% 6.7°C 0mm 74% 0cm 50° 11°C 0.69mm 0.35kPa 23656m 9.2m/s 7.2m/s
12:00
3% 6.8°C 0mm 73% 0cm 57° 11°C 0.81mm 0.36kPa 23908m 9.5m/s 8.1m/s
13:00
2% 7°C 0mm 73% 0cm 60° 12°C 0.94mm 0.38kPa 24135m 9.6m/s 8.1m/s
14:00
9% 6.9°C 0mm 70% 0cm 59° 12°C 0.06mm 0.44kPa 24134m 9.7m/s 7.7m/s
15:00
17% 7.1°C 0.01mm 69% 0cm 54° 13°C 0.19mm 0.45kPa 24134m 9.8m/s 7.8m/s
16:00
24% 7.3°C 0mm 70% 0cm 47° 13°C 0.31mm 0.44kPa 24117m 9.7m/s 7.6m/s
17:00
21% 7.4°C 0.01mm 70% 0cm 38° 13°C 0.38mm 0.45kPa 24134m 9.6m/s 7.3m/s
18:00
19% 7.5°C 0mm 70% 0cm 30° 13°C 0.44mm 0.44kPa 24135m 8.9m/s 6.6m/s
19:00
16% 8.2°C 0mm 74% 0cm 21° 13°C 0.56mm 0.38kPa 24043m 8.3m/s 5.9m/s
20:00
19% 8.4°C 0.01mm 78% 0cm 12° 12°C 0.06mm 0.31kPa 24135m 7.2m/s 4.6m/s
21:00
21% 8.2°C 0mm 81% 0cm 4.3° 11°C 0.13mm 0.25kPa 24134m 6.4m/s 4.1m/s
22:00 ☾
24% 7.6°C 0mm 82% 0cm -2.7° 10°C 0.13mm 0.22kPa 24135m 5.9m/s 4.2m/s
23:00 ☾
21% 7.7°C 0.01mm 81% 0cm -8.2° 11°C 0.13mm 0.25kPa 24135m 5.7m/s 4.1m/s
Thu, Jun 11 Sunrise 04:50 Sunset 21:41
24:00 ☾
17% 7.5°C 0mm 82% 0cm -12° 10°C 0.13mm 0.23kPa 24134m 5.9m/s 4.1m/s
01:00 ☾
14% 7.7°C 0mm 84% 0cm -14° 10°C 0.13mm 0.2kPa 24134m 7.3m/s 4.5m/s
02:00 ☾
11% 8.5°C 0.64mm 89% 0cm -13° 10°C 2.1mm 0.14kPa 16142m 9.5m/s 4.8m/s
03:00 ☾
7% 9.2°C 1.3mm 94% 0cm -10° 10°C 4mm 0.08kPa 8150m 12m/s 5.1m/s
04:00 ☾
4% 9.9°C 1.9mm 99% 0cm -5.8° 10°C 5.9mm 0.02kPa 159m 14m/s 5.4m/s
05:00
3% 11°C 1.9mm 99% 0cm 0.77° 11°C 7.6mm 0.02kPa 139m 12m/s 4.7m/s
06:00
2% 11°C 2mm 99% 0cm 7.9° 11°C 9.2mm 0.01kPa 120m 11m/s 4.1m/s
07:00
1% 12°C 2mm 99% 0cm 16° 12°C 11mm 0.01kPa 100m 9m/s 3.4m/s
08:00
1% 12°C 1.4mm 99% 0cm 25° 12°C 7.8mm 0.02kPa 105m 10m/s 4.2m/s
09:00
0% 13°C 0.74mm 99% 0cm 34° 13°C 4.8mm 0.02kPa 111m 11m/s 5m/s
10:00
0% 13°C 0.12mm 98% 0cm 43° 13°C 1.8mm 0.03kPa 116m 12m/s 5.7m/s
11:00
0% 13°C 0.1mm 96% 0cm 50° 13°C 1.9mm 0.07kPa 7580m 12m/s 5.7m/s
12:00
0% 13°C 0.07mm 93% 0cm 57° 14°C 1.9mm 0.11kPa 15045m 12m/s 5.7m/s
13:00
0% 13°C 0.05mm 90% 0cm 60° 14°C 2mm 0.16kPa 22510m 12m/s 5.7m/s
14:00
0% 12°C 0.04mm 90% 0cm 59° 13°C 1.4mm 0.15kPa 23052m 11m/s 5m/s
15:00
0% 11°C 0.02mm 90% 0cm 54° 13°C 0.75mm 0.14kPa 23593m 11m/s 4.3m/s
How to read: these inputs help produce the derived score; they are not requirements by themselves.

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