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Snowdonia

Weather hazards over 300m on Thu 28 Jul 2016

High risk

Persistent extensive hill fog
Persistent during the morning, and returning during the evening. Difficult navigation likely.

Medium risk

Heavy persistent rain
Heavy rain possible Thursday morning. Slippery rocks and paths likely.

Low risk

Strong sunlight
Some afternoon brighter spells, will lead to a risk of sunburn

No risk

Blizzards
none
Heavy snow
none
Storm force winds
none
Gales
none
Severe chill effect
none
Thunderstorms
none

Thu 28 Jul 2016

Outbreaks of rain are likely to turn persistent and occasionally heavy across the park this morning, with hill fog enveloping even modest levels. Whilst this should clear by the afternoon, sunny spells will be slow to develop. One or two further heavy showers are then also likely, before rain and hill fog returns around dusk.

Time
0600 to 0900 0900 to 1200 1200 to 1500 1500 to 1800 1800 to 2100 2100 to 2400
Weather
Heavy rain Heavy rain Sunny intervals Heavy shower day Sunny intervals Light shower night
Precipitation probability
60% 80% 30% 40% 10% 40%

Visibility

Poor to very poor for much of the day, increasing to moderate to good at times during the afternoon.

Hill Fog

Blanket at 500m at first, descending to 300m by dawn. Ragged patches as low as 200m with the heaviest rain. Lifting to 500m during the afternoon, and becoming well broken with some brighter spells. However thickening again around dusk, and descending to 400m by midnight.

Max wind above 500m

Southerly 30-35mph becoming westerly 25mph by midday.

Temperature

Valleys:
Plus 13 Celsius becoming Plus 19 Celsius
800m:
Plus 9 Celsius
Freezing level:
Above the summits.

Fri 29 Jul 2016

Extensive low cloud and persistent rain or drizzle at first, and only gradually clearing southeast by mid-morning. Some warm sunshine is then likely across the park. This will lead to cloud bubbling up and one or two showers developing by the evening, although much of the park will remain dry once the initial rain has passed. There will also be moderate UV levels.

Visibility

Poor to very poor at first, clearing to good to very good by the afternoon. Becoming moderate in any showers.

Hill Fog

Blanket at 400m, with ragged patches down to 200m, mainly in the northwest, during the morning. This clearing south with cloud breaking across the park and hill fog burning away. Whilst highest slopes (above 800m) could remain shrouded into the afternoon, and again during any showers, all hills are likely to see some clear tops by the late afternoon.

Max wind above 500m

Northwesterly 20mph

Temperature

Valleys:
Plus 12 Celsius becoming Plus 17 Celsius
800m:
Plus 8 Celsius
Freezing level:
Above the summits.

Sat 30 Jul 2016

Sunny spells and scattered showers likely through the day, the heaviest showers most likely in the afternoon. Only limited amounts of hill fog expected, but there will be a fresh northwesterly breeze.

Sun 31 Jul 2016

Very little change is expected from Saturday, with further showers moving across the park on the cool northwesterly breeze. However these are likely to be generally lighter than on Saturday.

Mon 01 Aug 2016

With the northwesterly winds continuing to bring showers across the park, it will be another similar day. However, possibly turning a little warmer with the breeze easing, and fewer showers into the afternoon.

Issued at: 0808 on Thu 28 Jul 2016