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Brecon Beacons

Confidence

High for a dull day Friday, with some rain later. Also for this clearing Saturday, before a period of wet weather early Sunday. However only moderate on details including timing. Moderate for cloudy and humid conditions thereafter.

  • Friday
  • Saturday
  • Further outlook

Friday 17 August 2018

Weather hazards

Poor visibility Medium likelihood Hide detail

Poor visibility presents challenging route finding conditions. Visibility could be significantly less than 50 metres in all directions with few or no visual references, especially on featureless moors or plateaux. Distances become hard to judge and cliff or cornice edges can be difficult to recognise. These conditions require good navigational skills. There is a risk of white-out conditions when mist or fog is combined with extensive snow cover.

Strong sunlight Low likelihood Show detail

Harmful UV levels from sunlight increase with altitude giving a greater risk of sunburn and eye damage, even on some overcast days. On breezy days, the cooling effect of wind on exposed skin may disguise any feeling of sunburn until it is too late. If there is snow cover, glare increases the effect of UV rays especially on the eyes. It is advisable to wear sun block, protective clothing such as a long-sleeved top and hat and have good quality eye protection.

Headline

Dry, bright morning. Becoming cloudy in afternoon with rain later. Strengthening winds.

Weather at 600m

06:00 09:00 12:00 15:00 18:00 21:00
Cloudy Sunny intervals Sunny intervals Overcast Cloudy Cloudy
10% 10% 20% 30% 40% 40%
Chance of precipitation
2,500 2,800 3,000 3,500 3,700 3,300
Freezing level (m)
The level above which snow is expected to settle or the ground is expected to be frozen

Wind speed and direction (mph) By altitude above mean sea level

06:00 09:00 12:00 15:00 18:00 21:00
600m W 12 15 W 16 20 W 18 24 SW 22 28 SW 21 27 SW 21 28
300m SW 7 14 W 11 21 W 12 24 SW 13 25 SW 12 25 SW 12 25
Valley W 6 15 W 10 21 W 11 23 SW 11 24 SW 11 24 SW 11 24

Temperature (°C) By altitude above mean sea level

06:00 09:00 12:00 15:00 18:00 21:00
600m 9 11 12 11 12 12
300m 11 14 15 14 14 14
Valley 12 15 16 15 15 15

Feels like temperature (°C) By altitude above mean sea level

06:00 09:00 12:00 15:00 18:00 21:00
600m 6 7 9 8 8 9
300m 10 12 13 12 12 12
Valley 11 13 14 13 14 14
Sunrise: 06:01   Sunset: 20:34
Moon phase: Waxing crescent

Weather

A bright or sunny start, although cloud will increase through the day. Most places remaining dry throughout, however some outbreaks of light rain or drizzle are likely to spread onto northwestern hills during the late afternoon and evening.

Chance of cloud-free mountain/hill tops at 600m

Greater than 90% at first, with sunny spells likely, and only patchy cloud around 600m. However this will thicken and descend during the afternoon, especially across northwestern hills. Falling to 30% in the west by dusk, with broken cloud at 600m with patches down to 500m during any rain, and 80% in the east.

Visibility

Very good at first, but reducing to just middle distance hills being visible during the afternoon, and falling to just a few kilometres in any rain later.

Meteorologist's view

Gusts around 40mph likely over summits from late afternoon. Temperatures reaching 22 Celsius in eastern valleys.

Recent rainfall

  • Location: Neuadd (Near Pontsticill)
  • Altitude: 353m
  • Measurement date: 03:00 on Fri 17 Aug 2018
  • Last 24 hours: 4.8mm
  • Last 48 hours: 18mm
  • Last 72 hours: 18.4mm

Rainfall data provided by Natural Resources Wales. The Met Office is not responsible for content provided by third parties and may remove this data without warning.

Saturday 18 August 2018

Sunrise: 06:02   Sunset: 20:32
Moon phase: First quarter

Weather

Rather cloudy overnight, but mostly dry, with only a few further outbreaks of rain or drizzle in the west. A mainly bright day then follows with some afternoon sunny spells likely, however cloud will increase again later in the day. Feeling humid.

Maximum wind speed expected

Southwesterly 25mph, with gusts around 40mph over summits, gradually decreasing to 10-15mph from early afternoon.

Chance of cloud-free mountain/hill tops at 600m

Around 30% at dawn with broken cloud around 500m and patches around 400m in the west. Chances improve to 80% or more by mid-morning with cloud mainly around 800m However these fall again to 70% towards midnight as cloud increases and lowers to around 600m.

Temperature

  • At 600m Plus 15 Celsius
  • Valley Around plus 13 Celsius at dawn rising to 24 Celsius
  • Freezing level Above the summits.

Visibility

Some good views of distant hills possible from lower levels, but visibility of just a few kilometres in overnight rain and drizzle.

Sunday 19 August 2018

Sunrise: 06:04   Sunset: 20:30
Moon phase: First quarter

Heavy rain overnight. This clearing east through the morning, with a few sunny spells possible during the afternoon, but staying rather cloudy. Feeling warm. Winds also becoming light.

Monday 20 August 2018

Sunrise: 06:06   Sunset: 20:28
Moon phase: First quarter

A cloudy day, with summits often shrouded and also occasional outbreaks of drizzle. Feeling warm and humid despite the dull conditions and a slight breeze. The best of any brighter spells in the east.

Tuesday 21 August 2018

Sunrise: 06:07   Sunset: 20:26
Moon phase: First quarter

Variable cloud and some sunny spells. Mostly dry, although a few showers and a risk of more persistent rain later. Cloud perhaps obscuring highest summits during any showers or rain. Light winds.

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