lowering

1. (of sky or environment) Dark and menacing.Examples: "The morning had been intensely hot, with but little wind; and the lowering gloomy aspect of the clouds appeared to indicate the approach of one of those sudden gales peculiar to tropical climates, and which, although of short duration, are generally productive of mischief."; "The wide prospect up stream was grey and lowering, the long still-distant waterfront of Dundee, and the Fife shore were alike colourless, and there was ample evidence of rough weather not far ahead."; "Ahead of us the lowering smoke-screen of Leeds and her gloomy satellites hung like an incubus over the land."Synonyms: gloomy, threatening