Here's why:
* Subjunctive mood is used to express hypothetical or uncertain situations, wishes, or commands.
* The sentence uses the conditional clause "If it were to rain tomorrow" to express a hypothetical situation that may or may not happen.
* The verb "were" is in the subjunctive mood because it is used to express a hypothetical condition rather than a factual statement.
Here's a breakdown:
* "If it were to rain tomorrow" (subjunctive mood, hypothetical condition)
* "the picnic would be canceled" (conditional mood, consequence of the hypothetical condition)
Let me know if you have any other sentences you'd like to analyze!