The phrase "black cloud" usually refers to a feeling of sadness, negativity, or trouble that hangs over a person or situation. It symbolizes a dark and gloomy aura that can bring down someone's mood or situation. Full definition
Helping to create a perpetual black cloud over the organization that may be difficult to recover from let alone restore sustainability. (buyerpersonainsights.com)
The concerns are one of the few black clouds hanging over what is a booming industry. (theguardian.com)
Of course with peak oil looming over us like an ominous black cloud, some are using this as an opportunity to push for more domestic drilling too. (treehugger.com)