We have four months of data (10 minute interval), this seems have nice pattern (at least for eye ball).
We are using STL to decompose the time series and apply "random walk" to project next month worth of data. Some how projected data is not following the input data pattern. Here is screenshot. The one marked with RED line is forecated output.
We couldn't figure out what behavior in input data might be causing this. Any help would be appreciated.
It is interesting that R also generating similar chart:
EDIT: I couldn't upload file, but here is link for data set.
EDIT As everyone commented, it seems there is steep increase in trend at the end of time series. Here is trend chart (trend values extracted by STL):