A Met Office spokesman said: “Frequent heavy snow showers are expected, along with very gusty winds and a chance of frequent lightning affecting some places.
“There is a small chance of longer journey times or cancellations as road, rail, air and ferry services are affected.
“There is a slight chance that power cuts may occur, with the potential to affect other services, such as mobile phone coverage
“There is a slight chance that some rural communities could become cut off.”
Storm Gladys is the fourth named storm in a week after Dudley, Eunice and Franklin all caused chaos.