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Snowdonia

Confidence

High for the general weather story this week. Lower confidence for when the rain will clear east on Tuesday and for timings of rain arriving on Friday.

  • This evening
  • Monday
  • Tuesday
  • Further outlook

Sunday 16 December 2018

Sunrise: 08:24   Sunset: 15:59
Moon phase: First quarter

Mainly cloudy with showery rain, falling as sleet or snow above 700m, but becoming mainly dry late in the evening. Fresh southerly winds, about 20mph, gusting 30mph on the summits.

Monday 17 December 2018

Weather hazards

Gales High likelihood Hide 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 Medium 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.

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.

Headline

Dry with sunny spells in morning, becoming windy with outbreaks of rain arriving in afternoon. Feeling cold.

Weather at 800m

00:00 03:00 06:00 09:00 12:00 15:00 18:00 21:00
Cloudy Partly cloudy night Partly cloudy night Sunny intervals Cloudy Light rain Light rain Light rain
30% 10% 10% 10% 10% 70% 70% 70%
Chance of precipitation
1,000 1,000 1,000 1,100 1,300 1,600 1,700 1,700
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

00:00 03:00 06:00 09:00 12:00 15:00 18:00 21:00
900m W 20 25 W 22 28 SW 23 29 S 25 31 S 34 43 S 38 49 S 40 52 S 46 59
600m SW 13 18 SW 15 20 SW 16 20 S 17 23 S 25 33 S 28 38 S 31 41 S 35 47
300m SW 6 17 SW 7 18 SW 7 16 S 8 17 S 13 29 S 15 34 S 15 37 S 18 43
Valley SW 6 17 SW 7 19 SW 7 16 S 9 17 S 13 30 S 15 33 S 16 37 S 18 43

Temperature (°C) By altitude above mean sea level

00:00 03:00 06:00 09:00 12:00 15:00 18:00 21:00
900m 1 1 1 2 2 3 5 5
600m 3 3 3 4 4 5 6 7
300m 5 5 4 5 7 7 8 9
Valley 6 6 6 6 8 8 9 10

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

00:00 03:00 06:00 09:00 12:00 15:00 18:00 21:00
900m -5 -6 -6 -5 -5 -4 -2 -3
600m -2 -2 -2 -2 -2 -1 1 1
300m 3 2 2 2 3 4 5 5
Valley 4 4 3 3 5 5 6 7
Sunrise: 08:25   Sunset: 15:59
Moon phase: First quarter

Weather

Dry in the early hours with clear spells then Monday morning will be dry with bright or sunny spells. Clouding over in the afternoon with patchy rain arriving from the west. Rain perhaps heavy for a time in the evening, but staying mostly light and intermittent.

Chance of cloud-free mountain/hill tops at 800m

80% in the morning with a few patches of low cloud. Becoming 30% during the afternoon with extensive cloud developing, bases 500-700m.

Visibility

Patchy early morning mist but otherwise good through the morning with excellent air clarity. Becoming poor at times from around mid-afternoon as rain and low cloud arrives.

Meteorologist's view

A quiet morning of weather but note that conditions will become more hazardous from mid-afternoon onwards as winds strengthen bringing a significant wind chill.

Ground conditions

No recent ground conditions report available.

Tuesday 18 December 2018

Sunrise: 08:26   Sunset: 16:00
Moon phase: Waxing gibbous

Weather

Very windy with extremely challenging walking conditions on high ground. Patchy rain in early hours but rain will become heavy and persistent by dawn and last for most of the day to give drenching conditions. Heavy rain clears away to the east in the afternoon followed by clear intervals and scattered showers, wintry on summits.

Maximum wind speed expected

Southerly average 50-60mph with gusts 80mph, easing through the afternoon to 20-30mph gusts 40mph.

Chance of cloud-free mountain/hill tops at 800m

Almost nil due to persistent cloud with bases 400-600m for most of the day. Becoming 70% through evening as cloud lifts and breaks up.

Temperature

  • At 800m Plus 5 Celsius, falling to Plus 2 Celsius after dark.
  • Valley Plus 9 or 10 Celsius, falling to Plus 2 Celsius after dark
  • Freezing level 1700m falling to 1100m in evening.

Visibility

Poor for most of the day with low cloud at height and often a few km or less at low levels. Becoming clearer later as rain moves away east in the afternoon.

Wednesday 19 December 2018

Sunrise: 08:27   Sunset: 16:00
Moon phase: Waxing gibbous

Bright spells and occasional showers, wintry above 600m. Feeling cold with fresh or strong southwesterly winds and freezing level 900m.

Thursday 20 December 2018

Sunrise: 08:27   Sunset: 16:00
Moon phase: Waxing gibbous

Another day of sunny intervals and occasional showers, wintry above 600m. Some showers heavy with hail or thunder possible. Feeling cold with strong west or southwesterly winds. Freezing level 900m

Friday 21 December 2018

Sunrise: 08:28   Sunset: 16:01
Moon phase: Full

A dry, bright and frosty start but rain, preceded by summit snow, is expected to spread east in the afternoon. Strengthening southwesterly winds.

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