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Brecon Beacons

Confidence

High confidence for a drier and generally sunny day Monday and for somewhat milder conditions to push in from west later Tuesday and during Wednesday, but lower confidence for timings.

  • Monday
  • Tuesday
  • Further outlook

Monday 11 December 2017

Weather hazards

Severe chill effect Medium likelihood Hide detail

Wind significantly lowers the ‘feels-like’ temperature relative to the actual temperature, with even moderate winds significantly adding to the chilling effect. Strong winds can result in a severe and debilitating wind chill many degrees below the actual temperature. This effect will be enhanced in rain or wet snow. Without protection, prolonged exposure could result in frost nip or frostbite on exposed parts of the body and/or hypothermia.

Poor visibility Medium likelihood Show 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

Snow clearing overnight to leave Monday cold but generally sunny.

Weather at 600m

06:00 09:00 12:00 15:00 18:00 21:00
Light snow Cloudy Sunny day Sunny day Clear night Clear night
10% 00% 00% 00% 00% 00%
Chance of precipitation
100 0 0 0 100 100
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 NE 28 34 N 24 30 N 19 25 N 16 22 N 15 21 NW 14 18
300m NE 13 28 N 13 28 N 9 17 NW 5 12 NW 6 10 W 6 10
Valley NE 11 27 N 12 27 N 8 19 W 5 13 W 6 10 W 6 10

Temperature (°C) By altitude above mean sea level

06:00 09:00 12:00 15:00 18:00 21:00
600m -3 -4 -3 -3 -3 -3
300m -2 -3 -1 -4 -5 -4
Valley -1 -2 -1 -3 -4 -3

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

06:00 09:00 12:00 15:00 18:00 21:00
600m -12 -13 -11 -10 -10 -9
300m -7 -9 -6 -7 -9 -7
Valley -6 -7 -5 -6 -8 -7
Sunrise: 08:11   Sunset: 16:03
Moon phase: Third quarter

Weather

Patchy cloud left in east at daybreak, but this will clear away in the morning to leave a dry day with long sunny spells. Dry and clear through the evening. Cold with a significant chill where exposed to the north or northeasterly winds.

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

Around 20% overnight with extensive cloud down to 400m or lower, but generally 80 t 100% by day with most cloud clearing away southwards in the morning.

Visibility

Poor perhaps very poor at times overnight but then very good or excellent through the day with most snow covered peaks easily seen.

Meteorologist's view

A cold day at all levels and a significant chill is possible where exposed to the wind, though generally light winds away from higher slopes

Recent rainfall

  • Location: Neuadd (Near Pontsticill)
  • Altitude: 353m
  • Measurement date: 03:00 on Sun 10 Dec 2017
  • Last 24 hours: 2.8mm
  • Last 48 hours: 5.4mm
  • Last 72 hours: 18mm

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.

Tuesday 12 December 2017

Sunrise: 08:12   Sunset: 16:03
Moon phase: Third quarter

Weather

A widespread and sharp frost at all heights but temperatures slowly rising over lower slopes in the morning with sunny spells though there could be the odd light snow shower and some freezing fog at lower levels will likely persist well into the afternoon. High cloud slowly filtering in from the west with cloud lowering onto western slopes by evening and becoming quite misty with outbreaks of rain, but falling as snow time down to around 400m.until later, but a thaw at lower levels. A significant chill on higher slopes.

Maximum wind speed expected

North or northeasterly 20mph at first, but becoming west or northwesterly 10mph in afternoon, but southwesterly 20mph later

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

Good chance until late afternoon with patchy cloud generally above summits, but less chance from late afternoon with cloud base lowering to between 500 and 700m. More patchy in east, but generally broken in west through the evening and lowering to 400m in rain and snow.

Temperature

  • At 600m Minus 1 slowly rising to plus 3 Celsius.
  • Valley Minus 5 slowly rising to plus 4 Celsius
  • Freezing level 200, rising to 500m in afternoon then 900m later

Visibility

Good or very good, though very poor where any fog persists and becoming

Wednesday 13 December 2017

Sunrise: 08:13   Sunset: 16:03
Moon phase: Third quarter

Cloudy start with outbreaks of rain and this will become more prolonged and heavier in the morning, especially over western slopes. Becoming brighter through the afternoon but scattered snow showers later. Strong southwesterly turning westerly in the afternoon with gales on higher summits later. Freezing level falling to 450m later.

Thursday 14 December 2017

Sunrise: 08:14   Sunset: 16:03
Moon phase: Waning crescent

Clear or sunny spells and wintry showers. Strong occasionally gale force westerly winds easing then turning northerly. Freezing level around 450m.

Friday 15 December 2017

Sunrise: 08:15   Sunset: 16:03
Moon phase: Waning crescent

Clear or sunny spells and the odd wintry shower at first with moderate north to northeasterly winds. Freezing level rising to around 600m.

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