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Snowdonia

Confidence

High confidence for spells of rain over the next few days and for being mild, but less confidence for how long the periods of wet conditions will last, especially after Tuesday.

  • This evening
  • Monday
  • Tuesday
  • Further outlook

Sunday 22 October 2017

Sunrise: 07:55   Sunset: 18:06
Moon phase: New

Dry with some clear spells into the evening but cloudy later with rain spreading from the west

Monday 23 October 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.

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.

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.

Heavy persistent rain Medium 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.

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

A wet, rather windy and murky start to the week but drier and brighter conditions developing Monday afternoon

Weather at 800m

00:00 03:00 06:00 09:00 12:00 15:00 18:00 21:00
Heavy rain Heavy rain Heavy rain Light rain Cloudy Sunny intervals Cloudy Cloudy
70% 90% 80% 60% 00% 00% 00% 20%
Chance of precipitation
2,800 3,000 3,000 2,500 1,900 1,700 1,600 2,200
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 SW 28 35 SW 34 42 SW 37 47 SW 30 39 W 26 34 W 22 29 SW 19 25 S 24 31
600m SW 19 25 SW 23 30 S 25 34 SW 22 30 W 19 27 SW 16 23 SW 14 20 S 18 25
300m SW 8 20 S 12 26 S 13 29 SW 11 26 W 11 25 SW 9 20 S 7 15 S 9 23
Valley SW 13 24 SW 22 39 SW 26 45 SW 20 35 W 21 36 SW 16 28 SW 12 21 SW 14 26

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 6 7 8 9 8 8 7 7
600m 8 9 10 11 10 10 9 9
300m 10 11 12 13 13 13 11 11
Valley 11 12 12 13 14 14 12 12

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 1 2 3 4 3 3 3 2
600m 4 5 6 7 7 7 6 5
300m 8 8 9 11 11 11 9 9
Valley 9 9 10 11 12 12 10 10
Sunrise: 07:57   Sunset: 18:04
Moon phase: Waxing crescent

Weather

Some heavy rain overnight and a wet start to Monday with murky conditions blown onto the hills with strong or gale force southwest winds. Rain will become lighter and more patchy through the morning and die out by lunchtime as winds turn more westerly. Brighter through the afternoon with some sunshine, but walking in some areas may be difficult, with full river courses and soggy ground after earlier rain. A god deal of high cloud through the afternoon however with thicker cloud spreading in from the southwest late evening.

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

Not much chance at first with extensive cloud down to 300 or 400m, but chance improving through the morning, with cloud breaking and base lifting late to around 800m by late morning. Much better chance in the afternoon and for much of the evening with patchy cloud base mostly above the tops, though thicker and lower cloud late evening

Visibility

Poor locally very poor at first, but gradually improving through the morning with good clarity to the air through the afternoon

Meteorologist's view

Strong to gale force winds expected with wind speeds likely to be a little stronger than tables suggest, especially in the morning. 300m wind speeds in particular will be stronger, generally around 25 gusts 35mph. There will also be a significant wind chill with the wet and windy conditions, even though it will be mild at all levels.

Ground conditions

No adverse ground conditions reported on 22 of Oct

Tuesday 24 October 2017

Sunrise: 07:58   Sunset: 18:02
Moon phase: Waxing crescent

Weather

Outbreaks of rain, heavy and prolonged at times, with extensive hill fog. Any drier interludes will be over eastern tops late in the day . Windy with gales at height, though winds easing during the afternoon.

Temperature

  • At 800m Plus 12
  • Valley Plus 16
  • Freezing level Well above the tops

Visibility

Generally poor with areas of hill fog even over modest hill heights, though eastern ranges will fair a little better, perhaps good at times later.

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

Low likelihood, with extensive cloud down to 500m, but periods 300m on western slopes. Best chance later in the day over easternmost hills where cloud will be a little more broken

Maximum wind speed expected

Southwesterly 50 gusts 65mph in the morning across many of the higher slopes, but closer to 30mph later in the afternoon.

Wednesday 25 October 2017

Sunrise: 08:00   Sunset: 18:00
Moon phase: Waxing crescent

A mostly dry start with some bright spells, but cloud will thicken to bring outbreaks of rain or drizzle and extensive low cloud and hill fog. Mostly fresh south south or southwesterly winds, though light and rather variable at times over eastern summits.

Thursday 26 October 2017

Sunrise: 08:02   Sunset: 17:58
Moon phase: Waxing crescent

Cloudy with patchy rain or drizzle and rather extensive low cloud and hill fog, but some drier and perhaps brighter interludes in the afternoon. Fresh to strong southwest winds, but falling light through the afternoon and feeling warm and rather muggy..

Friday 27 October 2017

Sunrise: 08:04   Sunset: 17:55
Moon phase: First quarter

Mainly cloudy, but some brighter spells, especially in the east and mainly dry, though there could be a little drizzle over western slopes at times. Light winds from the west or southwest, but fresher southerly winds later.

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