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Rule Fog Hunter

Dolbadarn Castle - Fog Hunter - Snowdonia (Eryri)

Llanberis, Wales, United Kingdom

Thick, moody fog for atmospheric forest and landscape shots

Currently

Real-time conditions
Dewpoint Spread0.7°C
Visibility24135 (Clear)
Relative Humidity95%
Wind Speed4.6m/s (calm conditions)

Upcoming Opportunities

When all conditions match, PhotoWeather marks an opportunity window.

Times shown in Europe/London
fog weather icon
Next opportunity
Dense Fog
Dolbadarn Castle
Wed, Apr 8 · 22:00–03:00 · 5h window
Medium confidence
67%
🌫️Fog Probability64.9-96.4%
Dewpoint Spread: 0.1°C
Visibility: 364 (Fog)
Relative Humidity: 99%
Wind Speed: 3.6m/s (calm conditions)
fog weather icon
Moderate Fog
Dolbadarn Castle
Sun, Apr 12 · 22:00–01:00
🌫️Fog Probability:62.7%
Low
fog weather icon
Moderate Fog
Dolbadarn Castle
Mon, Apr 13 · 18:00–19:00
🌫️Fog Probability:69%
Low
fog weather icon
Dense Fog at Sunset
Dolbadarn Castle
Mon, Apr 13 · 19:00–21:00
🌫️Fog Probability:83.5-88.6%
High
fog weather icon
Dense Fog
Dolbadarn Castle
Mon, Apr 13 · 21:00–02:00
🌫️Fog Probability:86-100%
High
fog weather icon
Moderate Fog
Dolbadarn Castle
Wed, Apr 15 · 16:00–17:00
🌫️Fog Probability:74.6%
Medium
fog weather icon
Moderate Fog at Sunset
Dolbadarn Castle
Wed, Apr 15 · 20:00–21:00
🌫️Fog Probability:83.6%
Medium
+4 more windows in the next 10 days

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
6matching hours in the next 95 hoursJump to next match
AND logic: all conditions required
Meets requirement
Misses requirement
Time
Europe/London
Fog Probability
≥ 60.0%
Wed, Apr 8
02:000%
03:000%
04:000%
05:0039%
06:0057%
07:0063%
08:000%
09:000%
10:000%
11:000%
12:000%
13:000%
14:000%
15:000%
16:000%
17:000%
18:000%
19:000%
20:0050%
21:0055%
22:0074%
23:00100%
Thu, Apr 9
24:00100%
01:0096%
02:0065%
03:0032%
04:0022%
05:000%
06:000%
07:000%
08:0019%
09:000%
10:000%
11:000%
12:000%
13:000%
14:000%
15:000%
16:000%
17:000%
18:000%
19:000%
20:000%
21:000%
22:000%
23:000%
Fri, Apr 10
24:000%
01:000%
02:000%
03:000%
04:000%
05:000%
06:000%
07:000%
08:000%
09:000%
10:000%
11:000%
12:000%
13:000%
14:000%
15:000%
16:000%
17:000%
18:000%
19:000%
20:000%
21:000%
22:000%
23:000%
Sat, Apr 11
24:000%
01:000%
02:000%
03:000%
04:000%
05:000%
06:000%
07:000%
08:000%
09:000%
10:000%
11:000%
12:000%
13:000%
14:000%
15:000%
16:000%
17:000%
18:000%
19:000%
20:000%
21:000%
22:000%
23:000%
Sun, Apr 12
24:000%
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
Thu, Apr 9 Sunrise 06:31 Sunset 20:05
03:00
0% 7°C 0mm 95% 0cm -26° 7.7°C 0mm 0.05kPa 24135m 7.2m/s 4.6m/s
04:00
0% 6.2°C 0mm 94% 0cm -20° 7.1°C 0mm 0.06kPa 24135m 8.2m/s 5.1m/s
05:00
0% 6°C 0mm 94% 0cm -13° 6.9°C 0mm 0.06kPa 24135m 9.3m/s 5.6m/s
06:00
0% 6.3°C 0mm 94% 0cm -5.3° 7.2°C 0mm 0.06kPa 24134m 11m/s 6.1m/s
07:00
0% 7°C 0mm 96% 0cm 3.6° 7.6°C 0mm 0.04kPa 14971m 11m/s 5.6m/s
08:00
0% 7.5°C 0.38mm 96% 0cm 12° 8°C 0.06mm 0.04kPa 692m 11m/s 5m/s
09:00
0% 7.9°C 0.22mm 98% 0cm 21° 8.2°C 1.1mm 0.02kPa 555m 9.9m/s 4.6m/s
10:00
0% 7.5°C 0.02mm 95% 0cm 30° 8.3°C 1.3mm 0.06kPa 22714m 9.9m/s 5.4m/s
11:00
0% 6.2°C 0mm 87% 0cm 37° 8.3°C 1.3mm 0.14kPa 24135m 9.3m/s 6.7m/s
12:00
0% 5.2°C 0mm 82% 0cm 42° 8.1°C 1.3mm 0.2kPa 24135m 9.5m/s 7.4m/s
13:00
0% 4.8°C 0mm 81% 0cm 44° 7.8°C 1.4mm 0.2kPa 16246m 9.8m/s 7.6m/s
14:00
0% 3.7°C 0mm 77% 0cm 44° 7.5°C 0.13mm 0.24kPa 24135m 9.5m/s 6.9m/s
15:00
0% 3.4°C 0mm 73% 0cm 40° 7.9°C 0.31mm 0.28kPa 22106m 9.9m/s 7.5m/s
16:00
0% 2.5°C 0mm 71% 0cm 34° 7.4°C 0.44mm 0.29kPa 24135m 11m/s 7.6m/s
17:00
0% 1.6°C 0mm 67% 0cm 26° 7.2°C 0.56mm 0.33kPa 24134m 11m/s 7.3m/s
18:00
1% 1.6°C 0mm 70% 0cm 18° 6.8°C 0.69mm 0.3kPa 24134m 11m/s 7.5m/s
19:00
1% 1°C 0mm 70% 0cm 6°C 0.81mm 0.28kPa 24135m 11m/s 7.9m/s
20:00
16% 0.4°C 0mm 71% 0cm 0.49° 5.2°C 0mm 0.26kPa 24135m 11m/s 6.6m/s
21:00
32% -0.2°C 0mm 69% 0cm -8.4° 5°C 0mm 0.27kPa 24134m 11m/s 6.8m/s
22:00
47% -0.4°C 0mm 69% 0cm -16° 4.8°C 0.06mm 0.27kPa 24134m 11m/s 7m/s
23:00
42% -0.5°C 0mm 71% 0cm -22° 4.4°C 0.13mm 0.24kPa 24135m 11m/s 7m/s
Fri, Apr 10 Sunrise 06:31 Sunset 20:05
24:00
37% -0.4°C 0mm 72% 0cm -27° 4.2°C 0.19mm 0.23kPa 24134m 9.5m/s 6.1m/s
01:00
32% -0.7°C 0mm 72% 0cm -29° 4°C 0.19mm 0.23kPa 24135m 9.2m/s 5.9m/s
02:00
24% -0.9°C 0mm 72% 0cm -28° 3.8°C 0mm 0.23kPa 24134m 7.7m/s 4.4m/s
03:00
15% -1.4°C 0mm 71% 0cm -25° 3.4°C 0mm 0.23kPa 24134m 6.3m/s 3.4m/s
04:00
7% -1.7°C 0mm 70% 0cm -20° 3.2°C 0mm 0.23kPa 24135m 3m/s 2.2m/s
05:00
5% -1.9°C 0mm 69% 0cm -13° 3.2°C 0mm 0.24kPa 24134m 1.9m/s 1.4m/s
06:00
2% -1.9°C 0mm 68% 0cm -5° 3.4°C 0mm 0.25kPa 24134m 1.1m/s 0.72m/s
07:00
0% -1.6°C 0mm 69% 0cm 3.9° 3.6°C 0mm 0.25kPa 24135m 1.2m/s 1.1m/s
08:00
0% -0.8°C 0mm 70% 0cm 13° 4.1°C 0mm 0.25kPa 24134m 2.4m/s 1.8m/s
09:00
0% -1°C 0mm 66% 0cm 22° 4.7°C 0mm 0.29kPa 24134m 4.2m/s 2.9m/s
10:00
0% -1°C 0mm 64% 0cm 30° 5.3°C 0mm 0.32kPa 24135m 5.5m/s 3.8m/s
11:00
0% -0.9°C 0mm 62% 0.02cm 37° 5.8°C 0mm 0.35kPa 24135m 6.5m/s 5.2m/s
12:00
0% -0.7°C 0mm 62% 0cm 42° 6°C 0mm 0.36kPa 23389m 7.4m/s 5.8m/s
13:00
0% -1.1°C 0mm 60% 0cm 45° 6.1°C 0mm 0.37kPa 24134m 8.6m/s 6.2m/s
14:00
0% 0.2°C 0mm 67% 0cm 44° 5.9°C 0mm 0.3kPa 24007m 9m/s 6.5m/s
15:00
0% 1.9°C 0mm 77% 0cm 40° 5.7°C 0.06mm 0.21kPa 7006m 9.8m/s 6.6m/s
16:00
0% 2.1°C 0.01mm 79% 0cm 34° 5.4°C 0.13mm 0.18kPa 20010m 10m/s 7.1m/s
17:00
0% 2.5°C 0.02mm 81% 0cm 27° 5.5°C 0.13mm 0.17kPa 24134m 10m/s 6.1m/s
18:00
0% 3.1°C 0.13mm 86% 0cm 18° 5.2°C 0.25mm 0.12kPa 24133m 11m/s 6m/s
19:00
0% 3.7°C 0.09mm 92% 0cm 9.3° 4.9°C 0.38mm 0.07kPa 24135m 13m/s 6.2m/s
20:00
0% 3.7°C 0.03mm 92% 0cm 0.71° 4.9°C 0.13mm 0.07kPa 24071m 13m/s 6.8m/s
21:00
0% 3.4°C 0.01mm 90% 0cm -8.2° 4.9°C 0.19mm 0.09kPa 24134m 14m/s 7.3m/s
22:00
0% 3°C 0.84mm 87% 0cm -16° 5°C 0.81mm 0.11kPa 12215m 18m/s 8.4m/s
23:00
0% 3.6°C 0.34mm 87% 0cm -22° 5.6°C 1.3mm 0.12kPa 18751m 19m/s 8.7m/s
Sat, Apr 11 Sunrise 06:29 Sunset 20:07
24:00
0% 4.7°C 0.96mm 88% 0cm -26° 6.6°C 1.7mm 0.12kPa 11488m 20m/s 10m/s
01:00
0% 5.8°C 1.1mm 91% 0cm -29° 7.1°C 2.5mm 0.09kPa 10727m 23m/s 13m/s
02:00
0% 3.6°C 1.9mm 94% 0cm -28° 4.6°C 2.1mm 0.05kPa 8017m 12m/s 8.5m/s
03:00
0% 3°C 0.15mm 82% 0cm -25° 5.8°C 2.8mm 0.16kPa 18880m 16m/s 9.1m/s
04:00
0% 1.6°C 0mm 76% 0cm -20° 5.5°C 2.8mm 0.22kPa 24135m 15m/s 9.1m/s
05:00
0% 1.6°C 0mm 80% 0cm -13° 4.9°C 2.9mm 0.18kPa 23942m 15m/s 9.7m/s
06:00
0% 1.2°C 0mm 82% 0cm -4.6° 4°C 3.1mm 0.14kPa 24135m 13m/s 9.4m/s
07:00
0% 1°C 0mm 84% 0cm 4.2° 3.5°C 3.1mm 0.13kPa 24135m 12m/s 8.6m/s
08:00
2% 1°C 0mm 81% 0cm 13° 4.1°C 2.2mm 0.16kPa 17284m 13m/s 8.4m/s
09:00
5% 1°C 0mm 78% 0cm 22° 4.6°C 1.3mm 0.19kPa 10433m 15m/s 8.2m/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 45° 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 0.94° 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 06:27 Sunset 20:09
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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