Learn Farsi: شاید در تهران برف ببارد.

The word shâyad means might or maybe. In Farsi, when you express a possibility using shâyad, the main verb of the sentence must change to the subjunctive form. This is why the verb takes the be- prefix instead of the usual mi- prefix used for regular present tense actions.

Does shâyad always go at the beginning of the sentence?

Generally, yes. Impersonal modal verbs like shâyad (might) and bâyad (must) usually sit at the start of the sentence or clause. The main action verb, like be-bârad, is pushed all the way to the end of the sentence.

Why do we need both barf and be-bârad to say it might snow?

In English, snow can be a noun or a verb. Farsi handles this differently. The word barf is strictly a noun meaning snow. To describe the action of snowing, Farsi pairs it with the verb bâridan, which means to rain, snow, or precipitate. You are literally saying snow might fall.

Why does the verb be-bârad end with -ad? Is there a word for it in this sentence?

The -ad ending is the verb suffix for he, she, or it. However, Farsi does not use an empty placeholder word like the English it for weather. Instead, the noun barf (snow) is the actual subject of the sentence. The verb ending matches the snow, so the sentence literally means maybe snow falls in Tehran.