For Viana do Castelo :
No gale warning.
For the night from Thursday to Friday N force 3 in the early part of the night becoming NNE force 2. Gusts reaching 11 knots in the early part of the night.
Slight sea. Low, fairly long swell from WNW. Good visibility becoming good in the middle of the night then good. Daytime of Friday 21 august : The weather will become more uncertain during the day.
Sunny becoming changeable in the afternoon. No precipitation in the morning, possibility of showers in late afternoon. In the evening, cloudy spells, sometimes dense.
Possibility of showers NNW force 2 becoming NW force 3 in the middle of the day then NNW. Gusts reaching 12 knots from the middle of the day. Slight sea becoming smooth to slight in the evening. Low, fairly long swell from WNW. Good visibility becoming excellent in the middle of the day.