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Brecon Beacons

Confidence

High for generally showery conditions through Wednesday and Thursday becoming low on Friday due to doubts over progress of a band of cloud, rain and developments thereafter.

  • Wednesday
  • Thursday
  • Further outlook

Wednesday 19 December 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.

Gales Low likelihood Show detail

Gale force winds (gusts over 50mph) make walking difficult and strenuous with a potential to be blown over by gusts. There is often a marked increase in winds through cols or on exposed ridges and summits. Distances can take longer to cover and compass bearings become harder to follow accurately.

Severe chill effect Low likelihood Show 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.

Heavy persistent rain Low likelihood Show detail

Heavy and persistent rain can lead to drenched clothing and footwear with waterproofs often becoming soaked through, especially if accompanied by strong winds. This can lead to significant loss of body heat and an increased likelihood of hypothermia. Terrain may turn increasingly boggy underfoot while streams can flood and become impassable. There may also be a risk of flooding in valleys or glens. If there is snow cover, a heightened avalanche hazard is possible and avalanche reports should be consulted where available.

Headline

Sunny spells and showers, perhaps prolonged later. Strong southerly winds.

Weather at 600m

06:00 09:00 12:00 15:00 18:00 21:00
Light shower night Light shower day Light shower day Heavy rain Heavy rain Heavy rain
30% 30% 30% 80% 80% 80%
Chance of precipitation
1,100 1,000 1,000 1,100 1,100 1,100
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 SW 17 23 SW 18 24 SW 22 30 SW 27 36 SW 22 31 SW 22 30
300m SW 8 20 SW 10 22 SW 13 26 SW 15 32 SW 13 28 SW 13 28
Valley SW 6 20 SW 9 22 SW 11 25 SW 13 30 SW 11 27 SW 12 28

Temperature (°C) By altitude above mean sea level

06:00 09:00 12:00 15:00 18:00 21:00
600m 4 3 4 4 3 3
300m 5 5 6 6 5 5
Valley 6 6 7 7 6 6

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

06:00 09:00 12:00 15:00 18:00 21:00
600m -1 -2 -2 -3 -3 -3
300m 2 2 3 2 1 1
Valley 3 3 4 3 3 2
Sunrise: 08:18   Sunset: 16:04
Moon phase: Waxing gibbous

Weather

A mostly cloudy morning with a mix of some bright spells and showers, the showers heavy at times and falling increasingly as sleet or snow above about 750m. During the afternoon the showers may merge to give some longer spells of rain, sleet and summit snow before turning more showery again during the evening.

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

Around 60% with occasional or periods above 600m. Chances fall to around 20% during the afternoon with cloud becoming periods above about 450m before rising again through the evening.

Visibility

Good or very good falling to just a few kilometres in rain and sleet showers and below one kilometre in summit snow.

Meteorologist's view

Gusts around 45mph over ridges and summits.

Thursday 20 December 2018

Sunrise: 08:18   Sunset: 16:04
Moon phase: Waxing gibbous

Weather

Clear spells and occasional showers, falling increasingly above about 750m as sleet and snow throughout the day, most frequent across western hills. The showers dying out during the evening.

Maximum wind speed expected

Westerly or southwesterly 25-30mph, gusts around 45mph over ridges and summits.

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

Around 60% with occasional or periods of cloud above 750m but nearer 60% across western hills with occasional or periods of cloud lowering to 600m at times.

Temperature

  • At 600m Around plus 5 Celsius
  • Valley Around plus 3 Celsius at dawn rising to plus 10 Celsius by day.
  • Freezing level Above the summits

Visibility

Good or very good to just a few kilometres in rain and sleet showers and around a kilometre in summit snow.

Friday 21 December 2018

Sunrise: 08:19   Sunset: 16:05
Moon phase: Full

Cloudy with outbreaks of rain clearing to sunny or clear spells and showers soon after dawn. Strong southerly winds veering southwesterly and touching gale force at times. Freezing level above summits

Saturday 22 December 2018

Sunrise: 08:19   Sunset: 16:05
Moon phase: Full

Clear or sunny spells and showers, wintry above about 750m. Strong to gale force westerly or southwesterly winds easing. Freezing level above the summits.

Sunday 23 December 2018

Sunrise: 08:20   Sunset: 16:06
Moon phase: Full

Mostly cloudy with showers or longer spells of rain. Occasionally strong southwesterly winds. Freezing level above the summits.

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