Difference in sentences using は+が vs は+は


So I've come across these two sentences:

>   1. 雨は降っていますが、雪は降っていません
>

and

>   2. 雨は降っていません。雪が降っています。
>

so what i think is happening is that the first sentence shows contrast.

in the first sentence, we simply introduce two topics and give information
about them.

in the second sentence we introduced one topic, and since we already mentioned
降っている it became old information and then we can use が to specify what does
come down/fall.

it's a sentence that doesnt come to contrast but to show
correction/specificity of the topic.

is that correct..?




With all due respect, I disagree with your analysis, especially of the second
sentence.

First of all, I don’t think the existence of the first part in each sentence
is very important. The question seems to have more to do with how to interpret
が and は in a negative sentence.

雪 **が** 降っています is a very natural, matter-of-fact sentence that states it is
snowing. However, its negative version 雪 **が** 降っていません sounds as if the state
described by 雪が降っています is the normal or expected state, but that state is
currently not fulfilled because snow is missing.

雪 **は** 降っていません, on the other hand, specifically negates 雪 as something that
is falling. Something else might be falling.

Your first sentence sounds natural because of this. 「雨は降っていますが、雪 **が**
降っていません」 would imply it is supposed to be snowing, too, and that would sound
weird.

Your second sentence could be either 「雨は降っていませんが、雪 **が** 降っています」 or
「雨は降っていませんが、雪 **は** 降っています」. The latter somewhat emphasizes the fact that snow
_is_ coming down from the sky although rain is not.

