Usually, expressions that use es + adjetivo + que (it’s + adjective + that) are subjunctive triggers.
The adjective used in this combination suggests an opinion, which triggers the use of the subjunctive mood. Let’s see some examples:
Es importante que vayas al médico si te sientes mal.
It’s important for you to go to the doctor if you feel sick.
Es posible que llueva esta tarde.
It’s possible that it will rain this afternoon.
This structure also works in the past and in the future:
Era probable que ella pudiera venir a la fiesta.
It was likely that she would be able to come to the party.
Será imprescindible que estudies para el examen final.
It will be essential that you study for the final exam.
