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
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.
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.
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.
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.
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
|Chance of precipitation|
Wind speed and direction (mph) By altitude above mean sea level
|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
Feels like temperature (°C) By altitude above mean sea level
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.
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.
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.
No adverse ground conditions reported on 28 of Jul
Saturday 29 July 2017
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.
- At 800m 9C
- Valley 9C rising to 19C.
- Freezing level Above the summits.
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.