angry clouds black cat black clouds blackening blocking the light breakers ahead broken mirror cardhouse cause for alarm clouding crisis danger danger sign dangerous ground darkening dimming early symptom eclipsing emergency endangerment extinguishment falling barometer gaping chasm halcyon bird hazard high sign house of cards imperilment jeopardy menace obfuscation obnubilation obscuration obscurement obumbration occulting omen overcast overclouding overshading overshadowing overshadowment owl pass peril pinch plight precursor predicament preliminary sign premonitory sign premonitory symptom prodroma prodrome quarantine flag quicksand rainbow raven red flag red light risk rocks ahead shading shadowing shooting star skull and crossbones storm clouds storm petrel stormy petrel strait symptom thin ice threat thundercloud thunderhead warning sign warning signal yellow flag yellow jack