Завтра вечером ожидается сильный ветер.

Вечером is the instrumental singular form of вечер. In Russian, parts of the day are very often used in the instrumental without a preposition to mean in the morning / in the evening / at night, etc.

So:

• утром = in the morning
• днём = in the daytime
• вечером = in the evening
• ночью = at night

That is why завтра вечером naturally means tomorrow evening.

Here завтра is an adverb of time, meaning tomorrow. It does not change form for case, number, or gender in this use.

So in завтра вечером, you have two time expressions together:

• завтра = tomorrow
• вечером = in the evening

Together they give a more specific time: tomorrow evening.

Ожидается is the 3rd person singular form of ожидаться. In sentences like this, it has a passive-like meaning: is expected.

The -ся ending often helps form this kind of impersonal or passive-style expression in Russian. Compare:

• Метеорологи ожидают сильный ветер = Meteorologists expect strong wind.
• Ожидается сильный ветер = Strong wind is expected.

So ожидается is very common in forecasts, reports, and formal announcements.

Because in this sentence сильный ветер is the grammatical subject of ожидается.

In English, the idea is strong wind is expected. Since strong wind is the subject, Russian uses the nominative:

• сильный = nominative masculine singular
• ветер = nominative masculine singular

If it were an active sentence with someone doing the expecting, then you would get the accusative:

• Метеорологи ожидают сильный ветер = Meteorologists expect strong wind.

But with ожидается, the thing expected becomes the subject.

It is singular because the subject, ветер, is singular.

Russian verbs agree with their subject in number, and in the past tense also in gender. Here:

• ветер = singular
• so ожидается = singular

If the subject were plural, the verb would also be plural:

• Завтра ожидаются дожди. = Rains are expected tomorrow / Rain showers are expected tomorrow.

Russian does not use a dummy subject like English it in sentences such as It is raining or It is windy.

English often requires it for grammar, even when it does not refer to anything real. Russian usually does not. In this sentence, there is no need for a placeholder subject.

Also, here the sentence already has a real subject: сильный ветер.

Formally, ожидается is a present-tense form. But because the sentence includes a future time expression, завтра вечером, the whole sentence is understood as referring to the future.

Russian often does this in forecasts, schedules, announcements, and news style. The time phrase makes the meaning clear.

This is similar to English sentences like:

• The train leaves tomorrow.
• Rain is expected tomorrow.

So the form is present, but the time reference is future.

Yes, absolutely.

• Завтра вечером будет сильный ветер = There will be strong wind tomorrow evening.
• Завтра вечером ожидается сильный ветер = Strong wind is expected tomorrow evening.

The difference is mostly in tone:

• будет is more direct and neutral: there will be
• ожидается sounds more like a forecast or prediction: is expected

In weather reports, ожидается is especially common.

No, Russian word order is flexible. The version you have is a very natural forecast/report style order:

• Завтра вечером ожидается сильный ветер.

It presents the time first, then the forecasted event.

Other orders are possible, but they shift emphasis:

• Сильный ветер ожидается завтра вечером.
  Emphasizes strong wind more.
• Ожидается сильный ветер завтра вечером.
  Also possible, but a bit less smooth in many contexts.

So the original sentence is a very standard, neutral choice.

Russian has no articles, so there is no separate word for a, an, or the.

That means сильный ветер can mean different things depending on context:

• strong wind
• a strong wind
• the strong wind

In a weather forecast, English also often uses no article in a general sense, so strong wind is a natural translation. But the Russian itself does not mark article meaning directly.

A natural stress pattern is:

ЗАвтра ВЕчером ожидаЕтся СИльный ВЕтер.

More precisely by word:

• зАвтра
• вЕчером
• ожидАется
• сИльный
• вЕтер

A rough pronunciation guide:

• завтра ≈ ZAF-tra
• вечером ≈ VYE-che-ram
• ожидается ≈ a-zhi-DA-ye-tsa
• сильный ≈ SEEL-nyy
• ветер ≈ VYE-ter

If you want to sound natural, make sure the stressed syllables are clear, especially in ожидАется and вЕтер.