a baleful look.
a by-election at a time highly unpropitious for the Government.
a dead and ominous silence prevailed.
a sinister smile.
forbidding thunderclouds.
his threatening behavior.
his tone became menacing.
ill omens.
ill predictions.
my words with inauspicious thunderings shook heaven.
ominous rumblings of discontent.
sinister storm clouds.
the situation became ugly.
ugly black clouds.