After recent snowfall at Kunzum Pass top, the stretch from Batal to Losar has been declared closed by officials for year 2016. Civilian traffic is now no longer allowed to travel on this stretch of the road. Even though the state run bus service from Manali to Kaza is now no longer operational, local cab drivers are still commuting on the road. This too however will stop after the snow at the top of the pass increases.
If you were planning a trip to Spiti, It is advised to travel from Shimla to Kaza and return via the same route. Do not risk travelling on Manali to Kaza stretch as it is quite risky right now. The road leading to Chandratal too is snowed out and there is no accommodation available at the lake anymore.
In my opinion, now is not really an ideal time to visit Spiti valley. If you are interested in catching some snow, then give it another couple of months and go in the month of January or February because at that time, the entire valley will be under a thick cover of snow. Right now, snow is only limited to the peaks like Kunzum Pass. The weather however has already gotten way too cold already.
Road from Manali to Keylong however is still open as Rohtang Pass has not yet been declared closed. Do not however plan anything as Rohtang too will close any day now.