Thank you, Tom3m.
I see you are not quite sure about the above...as well as I am...
Anyway, I am really apreciate your willingness to help!
In my opinion, the first sentence and the second one both fit the typical pattern of the second conditional, althoug they look a bit unusual, especialy the second sentence.
As far as I can see, the second conditioanal, as pattern, always contains, in the IF-clause, a past tense that should be an instance of the past subjunctive, and yet there are no restrictions to add adverbials or/and complements; anyway it always refers to the present or future.
Your example with 'be to + infinitive'-structure is also interesting... Still I think that my example with the past subjunctive 'were to + infinitive' is not that the same thing... Yes, the 'be to do'-structure is definitely a common modal construction, which can express different things depending on the context and taking into account the tense(as well as mood) in which it may appear.
Going on with the topic, I can suppose
the first sentence expresses the absence of the likelihood at the moment of speaking, as if the speaker knows it for shure in advance, for instance from the daily weather forecast, that it won't be fine tommorow. I also suppose that 'it were to be fine' should make the future reference stronger (perhaps excessively).
Assuming that the past subjunctive always refers to the present, I was a bit confused when I run into such a case with a future reference in the IF-clase.
By the way, what whoud you have made of it, if there hadn't been any adverbial of time? Just as follows:
'If it were fine, we would go to the park'. For me, this rather implies some nearest moment of time in the present than such a distant point as 'tomorrow'; it doesn't necessarily mean that it will be so fine tomorrow.
Should it still seem not so obvious, I will change the context : #3)
If I were you, I wouldn't do it. In this case we can't be so sure about what time point it suggests (I am not you and I will never be you)
And one more couple of examples:
#4)
If I had quite a bit of money, I would buy this car [
either now or the next day - it is not clear and is probably not so important].
#5)
If I were to get pots of money, I would fly to the moon. In my opinion, it depicts the future - relatively distant future possibility that is doubtful in terms of getting money.