I took your 29 days (oldest to newest) and found that there were 3 unusual days thus the following equation [![enter image description here][1]][1] with Actual/Fit and Forecast here [![enter image description here][2]][2] All models are wrong ... but some are useful .... . It is fundamentally an autoregressive process of order 1 after one has adjusted for the three "unusual data points " see [![enter image description here][3]][3] for a clear support for the anomaly identification. Plot of the residuals [![enter image description here][4]][4]from the above model suggesting reduced variability is clearly obvious . It is reasonable to suggest that there has been a break-point in the model error variance suggesting GLS or a weighted model . This was not not investigated here due to sample size ! ). Here is the plot of the original data [![enter image description here][5]][5] [![enter image description here][6]][6] [1]: https://i.sstatic.net/TvkN3.png [2]: https://i.sstatic.net/gS3mW.png [3]: https://i.sstatic.net/bhMsF.png [4]: https://i.sstatic.net/quJM6.png [5]: https://i.sstatic.net/VE2l3.png [6]: https://i.sstatic.net/sYVcc.png