1) Option chain data: On PUT side, Highest OI and Put writing are understandably at 27500 but on CALL side things are jumbled up. Highest Total OI is at 28000 but highest call writing is seen at 28100 with highest call unwinding at 28200, which in turn has 2nd highest total OI. My interpretation is that more Call writers are finding 28000 & 28100 as credible resistances. So for tomorrow's expiry 27500 to 28100 looks like big range.
2) Charts: Banknifty was much more stronger today than Nifty and finished as a strong green candle with HH and HL, scaling and closing above 20 (27685). By closing above this level now there is not much resistance left till 28250. So tomorrow being expiry, a wild move can take BNF till 28100 easily. There are no clear cut buying areas as such but 20 line can act as support so we can buy there with strict SL of around 60 points.
All the best.Happy trading.