That is a somewhat special case. The ordinary use of doch is a contradicting answer to a negative question. Example:
Kommst heute nicht mehr ins Büro. Doch, ich komme später noch einmal rein.
In Bavarian, oh jå is used the same way.
In the above case, doch is an agreeing answer to the negative question (the speaker indeed intended to leave and the ned/nicht in the question isn't really a negotiation but a flavouring particle) but the speaker adds a caviat (in the end, they didn't leave because of the bad weather). In standard German, this special meaning is triggered by doch being immediately followed by aber (but) and in Bavarian by jå immediately followed by åwa. This special meaning is in both languages normally reinforced by a specific prosody, which includes a lengthened pronunciation of doch/jå (yeeeees but...). But this lengthening is prosodic and not phonemic. Bavarian has no phonemic vowel length. This may be accompanied by raising or å from [ɔ]~[ɒ] to [o]. But this also isn't phonemic and it is optional. I find the phonemic transcription /o:/ misleading.
Also, the sample sentence contains errors: schlecht isn't really a Bavarian word. In this sentence one would say schiach and not schlecht. The standard German version contains two typos (furt instead of fort and is instead of ist).