The heavy rain was a forerun event for the upcoming storm.
forerun sign
Frequency:
60
%
The increased tension between the two countries was a forerun sign of potential conflict.
forerun indicator
Frequency:
45
%
The sudden drop in temperature was a forerun indicator of the approaching cold front.
Idiomatic Expressions for forerun
Phrase: forerunner of things to come
Meaning: something that serves as an indication or prediction of future events or developments
Usage: The recent protests are seen as a forerunner of things to come in the country.