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Snowdonia mountain area forecast

Forecast issued: 0415 on Wednesday, 27 August 2014

Overview for Wednesday

Fine and dry although breezy for much of the day with some sunshine. Increasingly cloudy through the afternoon though, with outbreaks of rain and strengthening winds during the evening.

Hazards

High risk of Gales: Southeasterly winds will bring mean speeds of around 50mph later.

High risk of Persistent extensive hill fog: Cloud bases will lower by the evening, mainly across eastern slopes.

Medium risk of Severe chill effect: Feeling closer to 5C in exposure to gale force southeasterly winds.

Low risk of Strong sunlight: Any prolonged spells of sunshine during the early afternoon may present a risk of sunburn.

No risk of Blizzards; Heavy snow; Storm force winds; Thunderstorms; Heavy persistent rain;

Weather summary and probability of precipitation for Wednesday

Dawn to 0900 Sunny intervals Sunny intervals 0% chance of precipitation
0900 to 1200 Sunny intervals Sunny intervals 0% chance of precipitation
1200 to 1500 Sunny intervals Sunny intervals 0% chance of precipitation
1500 to dusk Cloudy Cloudy 10-30% chance of precipitation

Detailed mountain weather forecast

Wednesday

Weather

Any early mist and fog patches will quickly lift, then remaining dry through much of the day, with some decent spells of sunshine, especially during the morning. Cloud will gradually build from the south later in the afternoon, lowering by evening with increasing amounts of hill fog. Outbreaks of rain will spread across the park later in the evening. Southeasterly winds will be gradually increase through the day, with gales developing through the afternoon and evening and bringing a pronounced chill effect.

Visibility

Poor within any early mist or fog patches. Generally good, but becoming moderate to poor in the rain later in the day, and very poor in hill fog.

Hill fog

Patches of fog below 500 metres at first, soon breaking and lifting after dawn. Otherwise, generally nil however bases will then lower from the southwest through the evening with widespread hill fog down to 500-700 metres after dusk.

Maximum winds above 500m

Southeasterly 30-35mph, increasing through the day to 45-50mph.

Temperature

Valleys: Plus 5 becoming 19 Celsius.
900 m: Plus 10 Celsius.
Freezing level: Above the summits.

Thursday

Weather

Outbreaks of rain will clear away during the early hours, with cloud gradually lifting and breaking around dawn. Some scattered showers are possible though, mainly through the morning, which may be heavy for a time. A largely dry and bright day will develop with some spells of warm sunshine. It will be rather breezy though, especially over exposed ridges and summits. Winds will strengthen further later in the evening.

Visibility

Good becoming very good, although temporarily reducing to moderate during any showers later in the day. Poor in any hill fog.

Hill fog

Bases 500-700 metres fairly widely at first, this soon breaking and mostly lifting above the summits with just patches around 500 metres by sunrise. Generally nil for the rest of the day, perhaps just patches down to 600 metres with showers later in the day.

Maximum winds above 500m

Southwesterly 30-35mph with gusts to 50-55mph near any showers.

Temperature

Valleys: Plus 9 becoming 19 Celsius.
900 m: Plus 9 Celsius.
Freezing level: Above the summits.

Outlook

Friday

Remaining unsettled and windy with scattered blustery showers. Some of these may turn thundery or merge into longer spells of rain. Hill fog is likely to be rather extensive, and gales are expected to develop during the morning leading to a significant chill effect.

Saturday

A brighter day than of late with sunny spells and a scattering of showers. The showers may ease from the west later in the day. Westerly winds will be much lighter than on Friday, although perhaps still gusty at times near showers.

Sunday

After a cool, dry and largely clear night, it should be a dry and bright morning. Increasing amounts of cloud will arrive in the west by the middle of the day though, with outbreaks of rain spreading eastwards across the park later. It will turn very windy leading to hazardous walking conditions with a chill effect.


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