Weather warnings may have been issued

Snowdonia

Confidence

High for conditions deteriorating Friday, with low cloud and rain spreading across Snowdonia, turning heavy and persistent. High for sunshine and blustery showers during the weekend, and the start of the coming week. Moderate confidence for heaviest and most frequent showers on Sunday.

Friday 28 July 2017

Weather hazards

Poor visibility High 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.

Heavy persistent rain High likelihood Show detail

Prolonged exposure to heavy rain can result in drenched clothing and a risk of hypothermia if not wearing good quality waterproofs. Terrain may turn increasingly boggy underfoot, while mountain streams will rapidly rise into spate and may 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.

Gales Medium likelihood Show detail

Progress will be impeded by very strong winds. Walking will be difficult and strenuous at times with a potential for one to be blown over in gusts. There can be a marked increase in winds through cols or on exposed ridges and summits. Distances often take longer to cover with compass bearings becoming more difficult to follow accurately.

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.

Forecast

Windy, with drier intervals and a few light showers at first. Cloud then lowering onto hills with heavy rain likely during the afternoon. Poor visibility developing.

Weather at 800m

06:00 09:00 12:00 15:00 18:00 21:00
Cloudy Cloudy Light shower day Heavy rain Heavy rain Light shower night
20% 20% 30% 80% 80% 40%
Chance of precipitation
1,900 1,800 2,400 2,900 2,900 2,300
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
900m SW 44 52 SW 34 42 SW 35 45 SW 33 42 SW 41 50 W 26 33
600m SW 31 38 SW 27 36 SW 28 37 SW 25 33 SW 29 37 W 18 24
300m SW 16 31 SW 15 32 SW 15 31 SW 13 28 SW 15 33 W 9 20
Valley SW 24 44 SW 26 47 SW 25 44 SW 23 40 SW 23 41 W 17 31

Temperature (°C) By altitude above mean sea level

06:00 09:00 12:00 15:00 18:00 21:00
900m 6 7 9 10 11 10
600m 9 10 11 12 13 12
300m 12 13 14 14 14 13
Valley 12 15 15 14 15 14

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

06:00 09:00 12:00 15:00 18:00 21:00
900m 0 2 4 5 6 6
600m 4 6 7 8 8 8
300m 9 10 11 12 12 12
Valley 9 12 13 12 13 13
Sunrise: 05:27   Sunset: 21:18
Moon phase: Waxing crescent

Weather

A rather cloudy start is expected, with a few showery outbreaks of rain. It will also be a windy start, leading to some impaired mobility across the highest peaks and ridges. Some brief brighter or sunny intervals are possible around midday, especially in the east. However conditions across the tops are then expected to deteriorate as an area of rain, heavy at times, spreads east during the afternoon. Cloud will gradually descend onto the hills, leading to some poor visibility across the summits. The rain will be coupled with some strong winds, leading to some poor late conditions, and perhaps some difficult descents.

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

80% at first, with cloud generally remaining above the hills. However this gradually falling to 30% by mid-afternoon, with cloud obscuring hills above 700m, and occasionally as low as 500m in the west. This only improving from the west after dusk, to 70% by midnight.

Visibility

Generally good at first, with hills at moderate distance visible. However becoming restricted to just nearby hills during the afternoon at lower levels due to rainfall. Very low visibility expected across the summits due to being shrouded with cloud.

Meteorologist's view

The best weather is likely through the morning, however it will still be breezy and occasionally wet. With conditions deteriorating in the afternoon, waterproofs are essential and plans for alternative, early descents are recommended.

Ground conditions

No adverse ground conditions reported on 28 of Jul

Saturday 29 July 2017

Sunrise: 05:28   Sunset: 21:16
Moon phase: Waxing crescent

Weather

Fine and dry overnight. Sunny spells are then likely through the day, but there will also be a few showers developing. Cloud is likely to occasionally obscure the very highest points, such as the summit of Snowdon, however there will be some breaks, to allow good views of some distant hills.

Temperature

  • At 800m 9C
  • Valley 9C rising to 19C.
  • Freezing level Above the summits.

Visibility

Good to very good, with distant hills often visible. This will reduce to moderate during any showers with views of some distant hills becoming restricted, however such reductions are likely to be brief.

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

90%, with spells of cloud only obscuring summits above 900m

Maximum wind speed expected

Southwest 20mph gusting 30-35mph.

Sunday 30 July 2017

Sunrise: 05:30   Sunset: 21:15
Moon phase: First quarter

Rather cloudy and windy with the best of any sunny intervals during the morning. Scattered showers are expected for much of the day and could be heavy and thundery during the afternoon. Feeling cool with fresh to strong southwesterly winds.

Monday 31 July 2017

Sunrise: 05:31   Sunset: 21:13
Moon phase: First quarter

Another day of sunny spells and showers although these should tend to be lighter and less frequent than on Sunday. Moderate to fresh southwesterly winds.

Tuesday 1 August 2017

Sunrise: 05:33   Sunset: 21:11
Moon phase: First quarter

Mainly dry with sunny spells and just a chance of the odd shower at times. Light to moderate southwesterly winds. Feeling a little warmer than previous days.

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