Snowdonia mountain area forecast
Forecast issued: 0458 on Thursday, 5 December 2013
Overview for Thursday
Strong winds, strengthening throughout, with storm force gusts at height. Rain from mid-morning, perhaps turning to snow as it clears later. Feeling very cold later, with icy surfaces developing.
High risk of Gales: Widespread gales developing throughout, with walking, even at low levels difficult, with buffeting.
High risk of Persistent extensive hill fog: Extensive. Becoming clearer in the afternoon as rain clears, but returning in showers.
Medium risk of Storm force winds: Increasingly treacherous above 500 m, with gusts exceeding 80 mph possible over high ridges later.
Medium risk of Severe chill effect: Strong winds and rain could bring severe chill, unless adequately equipped.
Medium risk of Heavy persistent rain: Rain becoming persistent this morning into the early afternoon.
Low risk of Thunderstorms: Band of rain during afternoon will include a low risk of isolated lighting strikes.
No risk of Blizzards; Heavy snow; Strong sunlight;
Weather summary and probability of precipitation for Thursday
|Dawn to 0900||Cloudy||20% chance of precipitation|
|0900 to 1200||Heavy Rain||60% chance of precipitation|
|1200 to 1500||Light rain||70% chance of precipitation|
|1500 to dusk||Heavy rain showers||40% chance of precipitation|
Detailed mountain weather forecast
Cold with many areas clear at first. However, cloud will spread into the hills during the morning, bringing hill fog and light but increasingly persistent rain. This will also be accompanied with a very strong wind, increasing to gale force, with storm force gusts at height. A band of blustery, perhaps heavy rain during the mid-to-late afternoon will then mark a boundary of cold air as it clears by evening. There may be some snow as it clears. Freezing levels will fall during the evening, and surfaces could turn icy, however, winds will begin to ease.
Good to start, but decreasing to poor in rain and very poor in hill fog. Visibility increasing to very good by midnight.
Well broken at first, at 500 m, however, increasing amounts during the day, especially during heavy rainfall. Becoming generally nil by midnight, however ragged patches to 500 m.
Maximum winds above 500m
Westerly 50 mph, increasing to westerly 70-80 mph over exposed ridges. Decreasing to Northwesterly 50 mph by dusk.
Valleys: Minus 2 Celsius, increasing to plus 7 Celsius, decreasing to plus 3 Celsius.
900 m: Minus 1 Celsius, increasing to plus 3 Celsius, decreasing to minus 3 Celsius.
Freezing level: Initially 900 m, increasing to above the summits, during the morning and early afternoon. However, falling to 400 m quickly after heavy rain clears.
Latest: 03/12/2013 17:54 Yr Wyddfa - Snowdon: Isolated patches of snow above 900m. Recommended to carry ice axe and crampons.
A few showers will continue overnight, perhaps falling as snow above 500 m. Surfaces are likely to be frozen during the morning, however, this will only be temporary as warmer air and outbreaks of rain returns from the southwest during the day. Hill fog is likely to become persistent in the west leading to further difficult conditions on the hills.
Initially excellent, although poor to very poor in hill fog. Decreasing to moderate, with outbreaks of rain and increasingly very poor as hill fog becomes extensive.
Ragged patches at 500 m during any morning showers, however becoming extensive at 600 m, especially in west by the evening.
Maximum winds above 500m
Northwesterly 40 mph.
Valleys: Minus 3 Celsius rising to plus 8 Celsius.
900 m: Minus 5 Celsius rising to plus 4 Celsius.
Freezing level: 500 m, increasing to above the summits by midnight.
A mainly cloudy, but milder, day across the park with the freezing level above the summits. Cloud is likely to shroud the hills at times during the day, leading to extensive hill fog. The cloud may well be thick enough for some drizzle in the west, although the best of the brightness will be in the east.
Rather cloudy throughout the day with some patchy light rain or drizzle possible at times. Fresh to strong west to southwesterly winds. Freezing levels above the summits.
Another cloudy day is expected, with further outbreaks of drizzle. However, winds are expected to slowly increase during the day, with upland gales becoming a risk by the evening. Freezing levels above the summits.